Important Questions - Metals Non metals

 

Ans: C

Q2.A non-metal X is an important constituent of our food. It forms two oxides Y and Z. Y is toxic and causes suffocation and even death while Z is responsible for global warming. Identify X, Y and Z.

(a)   X=C,Y=CO,Z=CO2

      (b)X=S,Y=SO2,Z=SO3

        ( c) X=p,Y=P2O3,Z=P2O5

       (d) X=O,Y=O2,Z=O3

Ans: A

 

 

 

 

Q3. A student adds an equal amount of copper sulphate solution in two beakers. He adds zinc in beaker P and silver in beaker Q. The student observes that the color of the solution in beaker P changes while no change is observed in beaker Q. Which option arranges the metals in increasing order of reactivity? *

(a) silver-zinc-copper    (b)zinc-copper- silver

 (c )silver-copper-zinc          (d)copper-silver-zinc

Ans: C

 

4. Which of the following is the correct arrange-ment of the given metals in ascending order of their reactivity?

Zinc, Iron, Magnesium, Sodium

(a) Zinc > Iron > Magnesium > Sodium

(b) Sodium > Magnesium > Iron > Zinc

(c) Sodium > Zinc > Magnesium > Iron

(d) Sodium > Magnesium > Zinc > Iron

Ans: D

 

 

 

 

 

 

 5. In thermite welding a mixture of …… and …… is ignited with a burning magnesium ribbon which produces molten iron metal as large amount of heat is evolved.

(a) iron (III) oxide and aluminium powder

(b) iron (II) oxide and aluminium powder

(c) iron (III) chloride and aluminium powder

(d) iron (III) sulphate and aluminium powder

Ans: A

 

 6. An alloy reacted with dilute hydrochloric acid to produce a gas which ‘pops’ a lighted splint. The residue reacted with dilute nitric acid to form a blue solution. Which one of the following pairs of metals is present in the alloy?

(a) Copper and lead

(b) Lead and magnesium

(c) Lead and zinc

(d) Copper and magnesium

Ans: d

7.  Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?

(i) Au

(ii) Cu

(iii) Na

(iv) K

(a) (i) and (ii)

(b) (i) and (iii)

(c) (ii) and (iii)

(d) (iii)and (iv)

Ans: a

 

 

 

Q8.Which one of the following four metals would be displaced from the solution of its salts by the other three metals?

(a) Mg

(b) Zn

(c) Ag

(d) Cu

Ans: C

Q9. A scientist is attempting to represent an ionic bond between calcium and chlorine. The figure below shows the progress he has made so far. What should be the next step in his representation of the ionic bond?

(a) Transfer an electron from the calcium atom to the chlorine atom.

(b). Transfer an electron from the chlorine atom to the calcium atom.

(c ) Add another chlorine atom to accept an electron from the calcium atom.

(d). Add another calcium atom to donate an electron to the chlorin​e

Ans: A

 

Q10.A student performs some activities on two substances and records the observations in a table as shown below:

 

Which option classifies the substance into metals and Non -Metals?

(a)Both substance are non metals

(b) both the substances are metals.

(c) substance M is a metal while N  is non metal substance

(d) M is a non metal while N is a metal

Ans: (c) substance M is a metal while N  is non metal substance

 

 

 

 

Q11. Which of the following two combinations are correct?

 

 

A. i and iii  B. i and iv  C. ii and iii  D. ii and iv

 

Ans: d

 

 

 

 

 

 

 

 

Q12. Which one of the following structure correctly depicts the compound cacl2​

 

Ans:D

 

 

 

Q13. Choose the incorrect match.

 (a) A metal used in joining electric wires - Magnesium

 (b) A metal whose oxide is soluble in both acids and bases - Zinc

(c) A metal unreactive towards oxygen and dilute acids - Gold

 (d) A metal extracted by using electrolytic reduction - Aluminium

Ans:A

 

Q14. What happens when calcium is treated with water?

(i) It does not react with water.

(ii) It reacts violently with water.

(iii) It reacts less violently with water.

(iv) Bubbles of hydrogen gas formed stick to the surface of calcium.

 (a) (i) and (iv) (b) (ii) and (iii) (c) (i) and (ii) (d) (iii) and (iv)

Ans: D

 

Q1. State the property utilised in the following:

(i) Graphite in making electrodes.

(ii) Electrical wires are coated with Polyvinyl Chloride (PVC) or a rubber-like material.

(iii) Metal alloys are used for making bells and strings of musical instruments.

 

Ans: i) Graphite is a non-metallic conductor of electricity 1 so is cheap, insoluble in water, acids and bases; and is non-corrosive material. Due to these properties, it is used in making electrodes.

(ii) Polyvinyl Chloride (PVC) or a rubber-like material are insulators and hence do not allow electrons to flow. Hence, these are used in coating the electrical wires.

(iii) Metals and metal alloys are generally sonorous in nature, i.e. they produce sound. Due to this property, they are used for making bells and strings of musical instruments.

 

 

Q2.     Choose the following metals to answer the questions below

(Aluminum, Copper, Calcium, Iron, Magnesium, Potassium, Nickel, Zinc)

Name a metal which

1. is manufactured by electrolysis of its molten oxide
2. is used to galvanaize Iron
3. is alloyed with Zinc to make Brass
4. reacts with aqueous copper(II)sulfate to give a pink solid
5. does not reacts with cold water

Ans: Metal manufactured by electrolysis of molten oxide is Aluminum

Metal used to galvanize the iron is Zinc

Metal alloyed with Zinc to make Brass is Copper

Metal reacts with aqueous copper(II)sulfate to give pink solid is Iron

 

Q3. A,B       and    C       are     3        elements     which          undergo      chemical          reactions    according   to      following equations:

 Answer      of      the     following:

i.        Which        element       is       most  reactive?

ii.       Which        element       is       least  reactive?

 Ans:

1)Reactivity series,B most reactiveA,C least reactive

2)B is the most reactive element

3) C is the least reactive element.

Q4. An element X on reacting with O2 form X2O. This Oxide dissolves in water and turns blue litmus paper red. Predict the nature of element whether it is a metal or a nonmetal.

Ans. The oxide is acidic in nature as it has turned blue litmus to red. Hence X is a nonmetal.

Q5. A metal ‘X’ is found in the form of filings which burns vigorously when sprinkle of flame. When these filings are treated with Sulphur a black colored compound ‘Y’ is formed which is not attracted by magnet. ‘X’ reacts with dil HCl to liberate hydrogen gas ‘X’ reacts with steam to from ‘Z’ along with hydrogen gas. Identify ‘X’, ‘Y’, and ‘Z’. Write the reaction  involved.

Elements 'X' is iron. Iron fillings burn vigorously when sprinkled on the flame. These react with sulphur to form ferrous sulphide which is a black colored compound.

Fe+S→FeS

Iron reacts with dil HCl to form ferrous chloride and hydrogen gas.

Fe+2HCl→FeCl2+H2

Iron reacts with steam to form Fe3O4and hydrogen gas 3Fe+4H2O→Fe3O4+4H2

So X is iron, Y is FeSand Z is Fe3O4

Q6. A chemical compound ‘X’ is used in the soap and glass industry. It is prepared from brine.

(a) Write the chemical name, common name and chemical formula of ‘X’.

(b) Write the equation involved in its preparation.(c) What happens when it is treated with water containing Ca and Mg salts?

Ans: (a) The chemical name is Sodium carbonate. Its common name is Washing Soda. The chemical formula of the compound in its hydrated form is Na2CO3 .10H2O   and the chemical formula in its anhydrous form is Na2CO3.

(b) Sodium carbonate is prepared in the industries by various processes. One such common process is the thermal decomposition of sodium bicarbonate. The reaction that is involved here is as follows:

 

Thus, in the manufacture process, we can find the use of brine (NaCl) in the production of sodium carbonate.

(c) As sodium carbonate is water-soluble and magnesium carbonate and calcium carbonate are insoluble, so it is used to soften water by removing Mg2+and Ca2+ Thus, when sodium carbonate is treated with water containing Ca and Mg salts, it removes them and thus, softens the water.

 

Q 7 Compounds containing oxygen are of great interest in the field of chemistry. Because of oxygen's high reactivity, it is most often found in compounds. Oxygen reacts rapidly with group 1 elements. All alkali metal oxides form basic solutions when dissolved in water. The principal combustion product is the most stable product with respect to the reactants. For example, with careful control of oxygen, the oxide M2O (where M represents any alkali metal) can be formed with any of the alkali metals. When a metal reacts with oxygen to form a metal oxide, a redox reaction occurs. Metal + Oxygen → Metal oxide Different metals burn in oxygen with different rates depending on their differing activeness. The more reactive metal towards oxygen, the brighter and faster the combustion of the metal. Given figure below shows the experiment is conducted to build the reactivity series of metals. Oxygen that is used in combustion of other metals is provided by heating solid potassium manganate (VII). When heated, lithium, sodium, potassium, rubidium, and cesium ignite through combustion reactions with oxygen. Glass wool Metal filing Heat up Heat up Potassium Manganate (VII) crystal

 

   Ans: (a) Metals such as silver and gold do not react with oxygen even at high temperatures as they are relatively inert. (b) Copper does not burn but is coated with black colored copper oxide. When heated, copper does not burn, but the hot copper metal is coated with a black coloured layer of copper (II) oxide. 2Cu + 02  2CuO (c) Almost all metals combine with oxygen to form metal oxides. Metal + Oxygen  Metal oxide Some metal oxides, such as sodium oxide and potassium oxide, dissolve in water to form alkalis: Moreover, some metal oxides, such as aluminium oxide and zinc oxide, show both acidic and basic nature and are known as amphoteric oxides. OR (c) The metal oxides sodium oxide and potassium oxide dissolve in water to form alkalis as follows: Na2O(s) + H20(l)  2NaOH(aq) K2O(s) + H20(l)  2 KOH(aq) 

 

Q8.A metal A, which is used in thermite process, when heated with oxygen gives an oxide B, which is amphoteric in nature. Identify A and B. Write down the reactions of oxide B with HCl and NaOH.

 

Aluminium and Iron are used in a thermite process, however, only aluminium when heated with oxygen, gives aluminium oxide, which is an amphoteric substance, meaning it can react with both acids and bases. Hence, A is aluminium and B is aluminium oxide.

 

The reaction of aluminium oxide with hydrochloric acid can be written as follows:

Al2O3+6HCl→2AlCl3+3H2O

The reaction of aluminium oxide with sodium hydroxide can be written as follows:

Al2O3+2NaOH→2NaAlO2+H2O

 

Q9.Give reasons: (i) Reactivity of Al decreases if it is dipped in HNO3. (ii) Carbon cannot reduce the oxides of Na or Mg. (iii) NaCl is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state. (iv) Iron articles are galvanised. (v) Metals like Na, K, Ca and Mg are never found in their free state in nature.

Ans: (a) Nitric acid is a strong oxidizing agent. Due to this, when aluminium is dipped in nitric acid, a layer of aluminium oxide is deposited on aluminium. As a result; reactivity of aluminium decreases when it is dipped in nitric acid.

(b) Sodium and magnesium are highly reactive metals. Hence, they have higher affinity to oxygen than to carbon. Due to this, carbon fails to reduce the oxides of sodium or magnesium.

(c)  NaCl is an ionic compound. Ionic compounds do not conduct electricity in solid state. But ionic compounds are good conductors of electricity in molten state and in aqueous solution.

(d) Iron has a tendency to react with atmospheric moisture. This process is called rusting and leads to corrosion of iron. Iron articles are galvanized to prevent rusting of iron.

(e) Na, K. Ca and Mg are highly reactive metals. They can easily form compound with most of the elements. Due to this, these metals are not found in their free state in nature.

 

 

Q10. (a) Write the chemical name of Na2CO3.10H2O and Na2CO3. (b) Write the significance of 10H2O. (c) Mention the term used for water molecules attached with a salt. (d) With the help of a chemical equation, explain the method of preparation of both Na2CO3.10H2O and Na2CO3. Also, list two uses of Na2CO3.10H2O.

 

Ans: Na2CO3.10H2O - Sodium carbonate decahydrate. Na2CO3 - Anhydrous sodium carbonate 10H2O - Water of crystallization which impacts shape and colour to the crystals. Preparation: NaCl + H2O + CO2 + NH3 → NH4CI +NaHCO3   2NaHCO3 +Heat→ Na2CO3 + H2O + CO2   Na2CO3 + 10H2O → Na2CO3.10H2O Uses: (i) Used in glass, soap and paper industries. (ii) Used in the manufacture of borax. (iii) Used as a cleansing agent for domestic Purpose.

 

Q11. Nikita took Zn, Al, Cu, Fe, Na and Mg metal. She then puts each metal win cold water and then in hot water. She reacted the metals with steam. 1) Name the metal(s) which reach with cold water 2)Name the metal(s) which react with steam 3)Name the metal(s) which react with hot water. 4)Arrange the metals in the decreasing order of their reactivity.

Ans. (i) Na (ii) Al, Zn, Fe (iii) Mg (iv) Na>Mg>Al>Zn>Fe>Cu

 

Q12. Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows.

Answer the following questions based on above information:

(i) Which is the most active metal and why?

(ii) What would be observed if B is added to a solution of copper (II) sulphate and why?

(iii) Arrange the metals A, B, C and D in order of increasing reactivity.

(iv) Container of which metal can be used to store both zinc sulphate solution and silver nitrate solution. Give reason for your choice.

(v) Which of the above solutions can be easily stored in a container made up of any of these metals?

 

 

Ans:

(a) So, from the following results, we can conclude that B is the most reactive metal.

 

 

(b) When B is added to the copper sulphate solution then it will displace copper from copper sulphate.

 

 

(c) Increasing order of reactivity of A, B, C, and D is:

D < C < A < B.

 

 

(d) As D is less reactive from all the metal, so D can be used as a container to store zinc sulphate and silver nitrate solutions.

 

 

(e) Zinc sulphate can be easily stored in a container made up of these metals.

 

 

 

 

 

 

HOT Questions -Acid Bases Questions

 Q1. The diagram shows the reaction between metal and dil. acid. What is the reason for different behaviour of Mg in test tube B ?

 

a. Mg is lighter element than dil. HCI.

b. Mg reacts with dil. HCl to produce H2 gas which helps in floating.

c. Mg reacts with dil. HC1 to produce N2 gas which helps in floating.

d. Mg reacts with dil. HCI to produce CO2 gas which helps in floating.

Ans: B 

Q2. A blue litmus paper was first dipped in dil. HCl and then in dil. NaOH solution. It was observed that the colour of the litmus paper 

a. changed first to red and then to blue 

b. changed to red 

c. remained blue in both the solutions 

d. changed first to red and then to blue

d. changed first to red and then to blue Explanation: Blue paper turn in red indicate the sample is acidic. Blue paper that does not change color indicates the sample is a base. HCl is acidic and NaOH is base, So, dil. HCl turns blue litmus red which becomes blue again in NaOH.

Q3. 5 mL of acetic acid was added to equal volume of water and the mixture was shaken well for one minute and allowed to settle. The correct representation of the observation made would be as given in test tube (1)

  

 a. III b. I c. II d. IV

         IV Explanation: Acetic acid dissolves in water forming clear solution.

Q4. On putting few drops of an unknown liquid on pH strip, the colour of pH strip changed to green. The liquid taken is likely to be 

a. pH paper shows green colour with water us neutral.

       b. dilute sodium hydroxide solution 

c. dilute hydrochloric acid 

d. lemon juice

     Q5What happens when a solution of an acid is mixed with a solution of a base in a test tube? 

(i) The temperature of the solution increases

(ii) The temperature of the solution decreases 

(iii) The temperature of the solution remains the same

(iv) Salt formation takes place

(a) (i) only (b) (i) and (iii) (c) (ii) and (iii) (d) (i) and (iv)

 Ans: (d) (i) and (iv) When acid is mixed with a solution of base it results in a neutralization reaction. Neutralization is an exothermic reaction which results in the formation of salt.

     Q6. A scientist in a chemistry lab wants to make salt of pH5.5 using acid and base. The table    shows the acid and base present in the lab.

1 HCL

2 NaOH

3 H2CO3

4 NH4OH

5 CH3COOH

 Which of the acid and base he should use for the reaction?

a. CH3COOH and NaOH

b. HCL and NaOH

c. H2CO3 and NaOH

d. HCL and NH4OH

Ans: (c) HCl and NH4OH    The salt having pH 5.5 is acidic. So, to prepare an acidic salt, a strong acid (HCl) and a weak base (NH4OH) is required.

Q7. Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained? 

  

Which of the following will turn phenolphthalein pink?

(a) NaOH(aq) (b) HCl(aq) (c) CH3COOH(aq) (d) H2O

Ans: (a) NaOH(aq)

Phenolphthalein solution is a colourless indicator which gives pink colour in basic solution.

Phenolphthalein solution remains colourless in acidic solution as well as in neutral solution.

Q8. Common salt besides being used in kitchen can also be used as the raw material for making:

 (i) washing soda (ii) bleaching powder (iii) baking soda (iv) slaked lime 

(a) (i) and (ii) (b) (i), (ii) and (iv) (c) (i) and (iii) (d) (i), (iii) and (iv) 

Ans: (c) (i) and (iii) The common salt obtained is an important raw material for various other materials of daily use, such as sodium hydroxide, baking soda, washing soda and many more.

Q9Ayush is putting in the test tube containing water whereas Piyush is putting water in the lest tube containing . Which of the two is likely to face danger?

(a) Piyush (b) Ayush (c) None of the two (d) Both Ayush and Piyush

 Ans: (a) Piyush Piyush is likely to face danger. Addition of water to concentrated sulphuric acid is an exothermic reaction and can lead to explosions. Water should not be poured into a container containing an acid

Q10. Anand took four colourless solutions P, Q, R and S, and performed the following tests. What is the definite conclusion that Anand can reach?

   

 

(a) Both P and S are salt solutions. 

(b) Both Q and S are basic solutions. 

(c) Both Q and R are salt solutions. 

(d) Both P and R are neutral solutions. 

Ans: (d) Both P and R are neutral solutions. Since there is no change in the colour of solution P and R with any of the indicators so they are neutral solutions.

Answer the following Questions:

. Q1. Case Study - 1 Sohan went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him, which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was sad but after a futile argument, the man beat a hasty retreat.

 (a) What is used for dissociation of gold? [1]

 (b) Why the weight of the bangle was reduced drastically? [1]

 (c) Aqua-regia is a strong oxidising agent. (True or False). [2] 

                                     OR

 (c) What is the other name of the solution (in Latin) used by that man posing as the goldsmith? Why is it so called? 

Ans: (a) Aqua regia is used for dissolving gold. Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid in the ratio of 1 : 3

b)As the gold from the bangles was dissolved in aqua-regia, their weight was reduced drastically. (c) True. Aqua Regia is a strong oxidising agent due to the formation of NOCl (Nitrosyl chloride) and chlorine produced by reaction of two acids. OR Goldsmith used a solution known as Aqua regia, which is known as royal water in Latin. This mixture was given its name (literally, royal water") by the alchemists because of its ability to dissolve gold. It is a red or yellowish liquid.

Q2. The primary reason behind the formation of the toxic foam is high phosphate content in the wastewater because of detergents used in dyeing industries, dhobi ghat and households. Yamuna’s pollution level is so bad that parts of it have been labelled ‘dead’ as there is no oxygen in it for aquatic life to survive. Study the passage and answer the questions that follow:

 (i) Give an idea about the pH value of the water of river Yamuna if the reason of froth is high content of detergents dissolved in it. What does it tell us about the concentration of hydroxide ion and hydronium ion? [2] 

(ii) The table provides the pH value of four solutions P, Q, R and S Solution pH value P 2 Q 9 R 5 S 11 

Arrange the solutions in increasing order of their hydronium ion concentration. [2] OR 

(ii) What is the effect of high content of phosphate ion in river Yamuna? [2]

 Ans: (i) Detergents being basic increase the pH of water above 7. It will have high concentration of hydroxide ion (OH–) and low concentration of hydronium ion (H3O+). (ii) Higher the pH , lower is the hydronium ion concentration. So, S < Q< R< P OR (ii) Phosphate ion increases the growth of algae which ultimately decrease the level of dissolved oxygen. 

Q3. (a) Write the chemical name of Na2CO3.10H2O and Na2CO3. (b) Write the significance of 10H2O. (c) Mention the term used for water molecules attached with a salt. (d) With the help of a chemical equation, explain the method of preparation of both Na2CO3.10H2O and Na2CO3. Also, list two uses of Na2CO3.10H2O.

 Ans:Na2CO3.10H2O - Sodium carbonate decahydrate. Na2CO3 - Anhydrous sodium carbonate 10H2O - Water of crystallization which impacts shape and colour to the crystals. Preparation: NaCl + H2O + CO2 + NH3 → NH4CI +NaHCO3   2NaHCO3 +Heat→ Na2CO3 + H2O + CO2   Na2CO3 + 10H2O → Na2CO3.10H2O Uses: (i) Used in glass, soap and paper industries. (ii) Used in the manufacture of borax. (iii) Used as a cleansing agent for domestic Purpose. 

Q4. (a) For the preparation of cakes, baking powder is used. If at home, your mother uses baking soda instead of baking powder, how will it affect the taste of the cake and why? (b) How is baking soda be converted into baking powder? (c) What makes the cake soft and spongy?

 Ans: (a) The cake will have a bitter taste because of the formation of Na2CO3 / sodium carbonate while baking / heating. (b) By adding tartaric acid. (c) The liberated CO2 gas.

Q5. The pH of a solution is a measure of its hydrogen ion (H+) concentration. It is measured generally using pH scale. The values on pH scale ranges from 0 to 14. A pH of 1 is very acidic and corresponds to a high concentration of H+ ions. A pH of 14 is very basic and corresponds to a low concentration of H+ ions. The pH of a neutral solution is 7. The table given below shows the pH and H+ ion concentration of some common aqueous solutions. The leftmost column shows the number of moles of H+ ions in 1 mole of liquid. The pH and Hydrogen ion (H+) Concentration of Some Solutions H+ Concentration (moles) pH Solution 10–1 1 10–2 2 Gastric (stomach) juice, cola, lemon juice 10–3 3 Vinegar 10–4 4 Tomato juice 10–5 5 Black coffee, rain water 10–6 6 Urine 10–7 7 Pure water 10–8 8 Sea water 10–9 9 Baking soda 10–10 10 10 –11 11 Milk of magnesia 10–12 12 Household bleach 10–13 13 Oven cleaner 10–14 14 (i) How is the hydrogen ion concentration and pH related to each other? (ii) On the basis of above table, arrange the following in the decreasing order of H+ concentration. Pure water, tomato juice, milk of magnesia, sea water (iii) A solution of pH 2 is filled in two separate beakers. A few drops of methyl orange and phenolphthalein are added into separate solutions. How will the colour of the indicators change? OR (iii) Two solutions X and Y have pH values of 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink?

 Ans: (i) pH is inversely proportional to the hydrogen ion concentration. (ii) The decreasing order of H+ concentration is Tomato juice > Pure water > Sea water > Milk of magnesia (iii) The solution of pH 2 is acidic in nature. So, the colour change is Methyl orange: red; phenolphthalein: colourless OR (iii) X will turn blue litmus to red because it is acidic in nature having pH value less than 7. Y will turn phenolphthalein from colourless to pink because it is basic in nature having pH value greater than 7

Q6. In an industrial process used for the manufacture of sodium hydroxide, a gas ‘A’ is formed as a by-product. The gas ‘A’ reacts with lime water to give a compound ‘B’ which is used as a bleaching agent in the chemical industry. Identify ‘A’ and ‘B’. Also give the chemical equations of the reactions involved

. Ans: A — Cl2 (Chlorine gas) B — CaOCl2 (Calcium oxychloride) 2NaCl + 2H2O → 2NaOH + Cl2 + H2 Cl2 + Ca(OH)2 → CaOCl2 + H2O

Q7. A chemical compound ‘X’ is used in the soap and glass industry. It is prepared from brine. (i) Write the chemical name, common name and chemical formula of ‘X’. (ii) Write the equation involved in its preparation. (iii) What happens when it is treated with water containing Ca or Mg salts? 

Ans: (i) Chemical Name – Sodium Carbonate decahydrate Common Name – Washing Soda Chemical Formula - Na2CO3 .10H2O (ii) NaCl + H2O + CO2 + NH3 ⎯⎯→ NH4Cl + NaHCO3 2NaHCO3 ⎯⎯⎯→ Heat Na2CO3 + H2O + CO2 Prepared by: M. S. KumarSwamy, TGT(Maths) Page - 8 - Na2CO3 + 10H2O ⎯⎯→ Na2CO3 .10H2O (iii) It helps in removing permanent hardness./ It forms insoluble Ca or Mg salts in the form of scum. 

Q8. A teacher provided acetic acid, water, lemon juice, aqueous solution of sodium hydrogen carbonate and sodium hydroxide to students in the school laboratory to determine the pH values of these substances using pH papers. One of the students reported the pH values of the given substances as 3, 12, 4, 8 and 14 respectively. Which one of these values is not correct? Write its correct value stating the reason. 

Ans: The pH value of water given is incorrect. Its correct value is 7 since it is neutral in nature.

Q9.Sahil took five solutions A, B, C, D and E and tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is: (a) Neutral (b) Strongly alkaline (c) Strongly acidic (d) Weakly acidic (E) Weakly alkaline? Arrange the pH in increasing order of hydrogen ion concentration. 

Ans: Given pH for the solutions are A = 4, B = 1, C = 11, D = 7, E = 9. Hydrogen ions concentration increases with decrease in pH value and thus strength of acid increases with decrease in pH value from 7 to 0. On the other hand, hydroxide ion’s concentration decreases with increase in pH value and thus strength of bases increases with increase in pH value from 7 to 14. While neutral solution has pH value = 7. Therefore, (a) Solution D is neutral having pH value equal to 7. (b) Solution C is strongly alkaline as its pH value is equal to 11 (c) Solution B is strongly acidic as its pH value is equal to 1 (d) Solution A is weakly acidic as its pH value is equal to 4 (e) Solution E is weakly alkaline as its pH value is equal to 9 Hence arrangement of given pH value in increasing order of hydrogen ion concentration: C (11) < E (9) < D (7) < A (4) < B (1) 30. 

Q10. Identify the acid and base which form sodium hydrogen carbonate. Write chemical equation in support of your answer. State whether this compound is acidic, basic or neutral. Also, write its pH value. 

Ans: Acid - H2CO3 Base - NaOH NaOH + H2CO3 → NaHCO3 + H2O Compound is basic in nature. pH value - ranges between 7 to 10

Q11. Manoj performed an experiment to understand that heat is produced when a few drops of concentrated sulphuric acid is slowly added into a beaker containing water. For this, he took 10 mL water in a beaker and added a few drops of concentrated H2SO4 to it. Then, he swirled the beaker slowly. During the process, a vigourous reaction takes place. It is an exothermic process. - (a) Why is it recommended that the acid should be added to water and not water to the acid? (b) How will the concentration of hydrogen ions gets affected if an acid is diluted? (c) What is this process called? Define the process. OR If we have hydrochloric acid and acetic acid of equal concentration, which will be a stronger acid and why? 

Ans: (a) Dilution of concentrated acid is an exothermic process. If water is added to a concentrated acid, the heat generated may cause the mixture to splash out and cause burns. When the acid is added to water slowly with constant stirring, the mixture will not splash out. (b) Concentration of H+ decreases with increase in dilution. (c) Dilution of the acid. Dilution of an acid or base means mixing an acid or base with water. This is done to decrease the concentration of ions (H3O + /OH- ) per unit volume. OR Hydrochloric acid will be a stronger acid, because it produces more H+ ions.

Q12. A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y, it gives a compound Z, used for disinfecting drinking water. Identify X, Y, G, and Z. (5)

Ans: The gas that is evolved at anode during the electrolysis of brine is chlorine. Hence, G is chlorine. When chlorine gas is passed over dry slaked lime - Ca(OH)2 , it produces bleaching powder which is used for disinfecting drinking water. Hence, Y is slaked lime (calcium hydroxide) and Z is calcium oxy-chloride (bleaching powder). Since Y and Z are calcium salts, therefore X is also a calcium salt. Since, X is a metal carbonate, it is calcium carbonate. Carbonates react with acids to produce carbon dioxide gas which when through a solution of slaked lime (Y) forms insoluble calcium carbonate. X Calcium carbonate Y Slaked lime (Calcium hydroxide) G Chlorine Z Calcium oxy-chloride (Bleaching powder)

HOT Based Questions Chemical Reactions and Equations

 

Take 3 g of barium hydroxide in a test tube, now add about 2 g of ammonium chloride and mix the contents with the help of a glass rod. Now touch the test tube from outside.
(i) What do you feel on touching the test tube?
(ii) State the inference about the type of reaction occurred.
(iii) Write the balanced chemical equation of the reaction involved. (Board Term I, 2017)
Answer:
(i) When barium hydroxide is added into ammonium chloride, the bottom of test tube is found to be cooler.
(ii) It is an endothermic reaction.
(iii) Ba(OH)₂ + 2NH₄Cl → BaCl₂ + 2NH₄OH

 

 

(i) Why is respiration considered as an exothermic reaction?
(ii) Write chemical name and the formula of the brown gas produced during thermal decomposition of lead nitrate.
(iii) Why do chips manufactures flush bags of chips with gas such as nitrogen? (Board Term I, 2015)
Answer:
(i) The glucose produced in our body during digestion combines with oxygen in the cells of our body and provides energy. The special name of this reaction is respiration. Thus respiration is an exothermic process because energy is produced during this process.
C6H₁₂O_6(aq) + 6O_2(g) → 6CO_2(g) + 6H₂O_(l) + Energy

Brown gas evolved is nitrogen dioxide (NO₂).

 

A water insoluble substance X on reaction with dilute hydrochloric acid released a colourless and odourless gas accompanied by brisk effervescence. When the gas passed through water, the solution obtained turns blue litmus red. On bubbling the gas trough lime water, it initially became milky and milkiness disappeared when the gas was passed in excess. Identify the substance X. Write the chemical equation of the reaction involved.

 

Here we will first find out the gas. It is stated that this gas turns lime water milky so it is sure that the gas is carbon dioxide (CO₂). 

When CO₂ reacts with water then carbonic aid is formed (H₂CO₃), which turns blue litmus red. 

CO₂ + H₂O → H₂CO₃ 

When CO₂ is passed through lime water (Ca(OH)₂) it turns it milky and on excess passing of carbon dioxide it forms calcium bicarbonate which forms a colourless solution, so the reaction is: 

Ca(OH)₂ + CO₂→ CaCO₃ + H₂O 

On passing in an excess amount 

CaCO₃ + H₂O + CO₂→ Ca(HCO₃)₂ 

For the identification of substance X, we know that in product carbon dioxide is there so there must be something of carbon must be there in reactant and X is water-insoluble so it should be calcium carbonate that is insoluble. 

So the reaction is: 

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂ 

X= CaCO₃

 

Compound ‘X’ decomposes to form compound ‘Y’ and CO₂ gas. Compound ‘Y’ is used in the manufacturing of cement.

(i) Name the compounds X and Y.

(ii) Write the chemical equation for this decomposition reaction.

Answer: Calcium carbonate (limestone) decomposes on heating to give calcium oxide and carbon dioxide.

CaCO₃ (s) ⎯→ CaO(s) + CO₂ (g)
calcium calcium   Carbon
Carbonate oxide  dioxide

A substance X, which is an oxide of a group 2 element, is used intensively in the cement industry. This element is present in bones also. On treatment with water it forms a solution which turns red litmus blue. Identify X and write the chemical reactions involved.

Answer: Element ‘X’ is calcium. When calcium oxide reacts with water it forms calcium hydroxide. Since calcium hydroxide is a base, thus it turns red litmus blue. Reaction involved in the reaction of calcium oxide with water can be written as follows:

CaO + H₂O ⇨ Ca(OH)₂ + Heat

Calcium belongs to group 2nd in periodic table. It is used in cement industry and also found in bones.

A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.

(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.

Answer:

2Mg + O₂ ⎯→ 2MgO

3Mg + N₂ ⎯→ Mg₃N₂

(a) X is MgO and Y is Mg₃N₂

(b) MgO + H₂O ⇨ Mg(OH)₂

ou are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute HNO₃, ZnCl₂ and H₂O. In which of the above containers these solutions can be kept?

Answer:

With Cu container:
The solution of dilute HCl, ZnCl₂ and H₂O can be kept in the container made of copper.  Since copper is a less reactive metal and is placed below the hydrogen in activity series.  It does not react with HCl, ZnCl2 and H2O.

Cu + HCl(dil)  -----------> No reaction

Cu + ZnCl₂  -------------> No reaction

Cu + H₂O  ----------------> Nop reaction

Cu reacts with dil HNO₃ and gets oxidised to give nitric oxide. HNO₃(dil) cannot be kept in copper container.

Cu(s)  +  8HNO₃(aq)  ——>  3Cu(NO₃)₂(aq)  +  2NO(g)  +  4H₂O(l)

With Al container:
While aluminium is highly reactive metal and reacts with HCl and ZnCl₂.

2Al + 6 HCl ----------> 2AlCl₃ + 3H₂ (g)

2Al + 3ZnCl₂ ---------> 2AlCl₃  + 3Zn

HNO₃ may be kept in Al container, since it forms a protective layer of Aluminium Oxide (Al₂O₃). It there is no layer of Al₂O₃ is there or breached, dil HNO₃ reacts with Al to form aluminium nitrate.

4Al   +  3O₂  --------> 2Al₂O₃ 
3Al + 4HNO₃ ----------> 3Al(NO₃)₃ + NO + 2H₂O

Aluminum metal rapidly develops a thin layer of aluminum oxide that prevents the metal from reacting with water. When this layer is breached a reaction develops, releasing highly flammable hydrogen gas.

2Al + 6H₂O -------> 2Al(OH)₃ + 3H₂

A solid substance P which is very hard is used in the construction of many buildings, especially flooring. When substance P is heated strongly, it decomposes to form another solid Q and a gas R is given out. Solid Q reacts with water with the release of a lot of heat to form a substance S. When gas R is passed into a clear solution of substance S, then a white precipitate of substance T is formed. The substance T has the same chemical composition as starting substance.
(i) What is substance P? Write its common name as well as chemical formula.
(ii) What is substance Q?
(iii) What is gas R?
(iv) What is substance S? What is its clear solution known as?
(v) What is substance T? Name any two natural forms in which substance occurs in nature.

(a) Calcium carbonate, limestone, CaCO3
(b) Calcium oxide, CaO
(c) Carbon dioxide, CO2
(d) Calcium hydroxide, Ca(OH)2 ;Lime water
(e) Calcium carbonate ; Limestone and Marble

 

 

A metal forms a salt XSO4. The salt XSO4 forms a clear solution in water which reacts with sodium hydroxide solution to form a blue precipitate Y. Metal X is used in making electric wires and alloys like brass.
(a) What do you think metal X could be?
(b) Write the name, formula and colour of salt XSO4.
(c) What is the blue precipitate Y?
(d) Write a chemical equation of the reaction which takes place when salt XSO4 reacts with sodium hydroxide solution. Give the state symbols of all the reactants and products which occur in the above equation.

(a) Metal X is Cu (Copper).

(b) Copper sulphate, CuSO4, Blue colour.

(c) Copper hydroxide, Cu(OH)2 it is a blue precipitate.

(d) CuSO4(aq)+2NaOH(aq)⟶Cu(OH)2(s)+Na2S04(aq)

 

A metal X forms a water soluble salt XNO3. When an aqueous solution of XNO3 is added to common salt solution, then a white precipitate of compound Y is formed along with sodium nitrate solution. Metal X is said to be the best conductor of electricity and it does not evolve hydrogen when put in dilute hydrochloric acid.
(a) What is metal X?
(b) What is salt XNO3?
(c) Name the compound Y.
(d) Write the chemical equation of the reaction which takes place on reacting XNO3 solution and common salt solution giving the physical states of all the reactants and products.
(e) What type of chemical reaction is illustrated by the above equation?

(a) Silver (Ag)
(b) Silver nitrate ( AgNO3)
(c) Silver chloride ( AgCl)
(d) AgNO3(aq)+NaCl(aq)⟶AgCl(s)+NaNO3(aq)
(e) Double displacement reaction.

 

 

 

 

 

 

 

 

Important Mcq of chemical reaction and equation

 

Q1.Which of the following is precipitation as well as double displacement reaction? a) NaOH + HNO3 → NaNO3+ H2O b) Cu + 2AgNO3 → Cu(NO3)2 + 2Ag c) 2Hg + O2 → 2 HgO d) FeCl3 + NH4OH → Fe(OH)3 + 3NH4Cl Ans: D

 

Q2. Exposure of silver chloride to sunlight for a long duration turns grey due to Which among the following statement(s) is(are) true?

1. the formation of silver by decomposition of silver chloride.

 2. Sublimation of silver chloride.

 3. Decomposition of chlorine gas from silver chloride.

4. Oxidation of silver chloride.

 (a) Only 1 (b) 1 and 3 (c) 2 and 3 (d) Only 4

Ans: a

 

Q3.Dissolution of sugar in water is a physical change. Physical changes are changes affecting the form of a chemical

substance but not its chemical composition    Fe2O3+2Al→Al2O3+2Fe

 

The above reaction is an example of a-

(a) combination reaction

(b) double displacement reaction

(c) decomposition reaction

(d) displacement reaction

 

Ans : d

 

Q4.Which of the following statements about the given reaction are correct?

3Fe(s)+4H2O(g)→Fe3O4(s)+4H2(g)

(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidizing agent

(a) (i), (ii) and (iii)
(b) (iii) and (iv)
(c) (i), (ii) and (iv)
(d) (ii) and (iv)

Ans: C

 

Q5.A shiny - brown substance X on heating in air turns black and a new compound Y is formed. Name the substance X and black compound Y.If hydrogen gas passed over it changes back to X

 

A X = Fe and Y = FeO

B X = Cu and Y = Cu(OH)₂

C X = Cu and Y = CuO

D X = Al and Y = AlO₃

Ans: C

 

 

 

 

Q6.Four students A,B,C and D were asked to carry out a decomposition reaction. Each one followed a different method as mentioned:

1: Heated an aqueous solution of iron sulfate in a test tube.

2. Added Zn granules to iron sulfate in a test tube and then heated the mixture.

3. Heated crystals of iron sulfate in a test tube.

4. Heated crystals of iron sulfate along with the copper sulfate crystals in a china dish. The student who adopted the correct method is:

 

1. 1
2. 2
3. 3
4. 4

 

Ans: C

 

Q7.Three beakers labelled as A, B and C each containing 25 ml of water were taken. A small amount of NaOH, anhydrous CuSO₄ and NaCl were added to the beakers A, B and C respectively. It was observed that there was an increase in the temperature of the solution contained in beakers A and B, whereas in case of beaker C, the temperature of the solution falls. Which one of the following statement(s) is (are) correct?
(i) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has occuBftd.
(iii) In beaker C exothermic process has occurred.
(iv) In beaker C endothermic process has occurred.
(a) (i) only
(b) (ii) only
(c) (i) and (iv)
(d) (iv), (ii) and (iii)

Answer

Answer: c

 

 

 

 

 

 

 

Q8.Name the products formed when iron filings are heated with dilute hydrochloric acid
(a) Fe (III) chloride and water
(b) Fe (II) chloride and water
(c) Fe (II) chloride and hydrogen gas
(d) Fe (III) chloride and hydrogen gas

Answer/ Explanation

Answer: d
Explaination: Reason: 2Fe + 6HCl → 2FeCl₃ (Iron (III) chloride) + 3H₂

 

Q9.A dilute ferrous sulphate solution was gradu¬ally added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disap¬pears. Which of the following is the correct explanation for the observation?
(a) KMnO₄ is an oxidising agent, it oxidises FeSO₄.
(b) FeSO₄ acts as an oxidising agent and oxidises KMNO₄.
(c) The colour disappears due to dilution; no reaction is involved.
(d) KMnO₄ is an unstable compound and de-composes in presence of FeSO₄. to a colourless compound.

Answer

Answer: a

 

Q10.Burning Magnesium ribbon is brought in the gas jar of carbon dioxide. Which of the following is correct ?

(i) It keeps on burning

(ii) It gets extinguished

(iii) Although CO2 is non-supporter of combustion but burning magnesium breaks CO2 into carbon and oxygen, oxygen helps in burning.

(iv) Carbon dioxide is a supporter of combustion.

(a) (i) and (iv)

(b) (i) and (iii)

(c) (i) and (ii)

(d) (iii) and (iv)

 

Answer

Answer: b