1. (a) What is the colour of ferrous sulphate crystals? How does
this colour change after heating?
(b) Name the products formed on strongly heating ferrous
sulphate crystals. What type of chemical reaction occurs in this
change
1. (a) What is the colour of ferrous sulphate crystals? How does this colour change after
heating?
(b) Name the products formed on strongly heating ferrous sulphate crystals. What type of
chemical reaction occurs in this change
ANSWER: (a) The colour of ferrous sulphate is green. It changes to brown after heating.
(b) The product formed is ferric oxide (Fe2O3). This is a decomposition reaction.
2. A student suffering from myopia is not able to see distinctly
the objects placed beyond 5 m. List two possible reasons due to
which this defect of vision may have arisen. With the help of ray
diagrams, explain
2. A student suffering from myopia is not able to see distinctly the objects placed beyond
5 m. List two possible reasons due to which this defect of vision may have arisen. With
the help of ray diagrams, explain
ANSWER: Two possible reason due to which the defect of vision may have arisen
are:
(1) increase in curvature of the lens.
(2) increase in length of the eyeball.
3. (a) Define excretion.
(b) Name the basic filtration unit present in the kidney.
(c) Draw excretory system in human beings and label the
following organs of excretory system which perform following
functions:
(i) form urine.
(ii) is a long tube which collects urine from kidney.
iii) store urine until it is passed out.
3. (a) Define excretion.
(b) Name the basic filtration unit present in the kidney.
(c) Draw excretory system in human beings and label the following organs of excretory
system which perform following functions: (i) form urine. (ii) is a long tube which collects
urine from kidney. iii) store urine until it is passed out.
ANSWER: (a) The biological process involved in
the removal of these harmful metabolic wastes
from the body is called excretion.
(b) The basic filtration unit in the kidney is known
as Nephron.
(c) i. kidney form urine.
ii. The ureter is the long tube which collects the
urine from Kidney.
iii. The urinary bladder is a structure which stores
the urine until it is passed.
(c)
4. Both soap and detergent are some type of salts. What is the
difference between them? Describe in brief the cleansing action
of soap. Why do soaps not form lather in hard water? List two
problems that arise due to the use of detergents instead of
soaps.
4. Both soap and detergent are some type of salts. What is the difference between them? Describe
in brief the cleansing action of soap. Why do soaps not form lather in hard water? List two
problems that arise due to the use of detergents instead of soaps.
ANSWER: Soaps are the sodium and potassium salts of long chain carboxylic acids
whereas detergents are ammonium or sulfonate salts.
Cleansing action of soap : One part of soap molecules is ionic and dissolves in water. The
other part is non-ionic hydrophobic part which dissolves in oil. Thus soap molecules
arrange themselves in the form of a micelle.
On rinsing with water soap is washed off, lifting the oily dirt particles with it. Soap does
not forms lather in hard water because it forms insoluble precipitate.
Problem due to the use of detergent are :
(i) Detergent are non-biodegradable. (ii) It leads to water or soil pollution
5. (i) Name and state the rule to determine the direction of
force experienced by a current carrying straight conductor
placed in a uniform magnetic field which is perpendicular to it.
(ii) An alpha particle while passing through a magnetic field
gets projected towards north. In which direction will an
electron project when it passes through the same magnetic
field?
5. (i) Name and state the rule to determine the direction of force experienced by a current
carrying straight conductor placed in a uniform magnetic field which is perpendicular to it.
(ii) An alpha particle while passing through a magnetic field gets projected towards north. In
which direction will an electron project when it passes through the same magnetic field?
ANSWER: (i) Fleming's left hand rule.
According to this rule : Stretch the thumb,
fore finger and middle finger of your left hand
such that they are mutually perpendicular. If
the forefinger points in the direction of
magnetic field and the middle finger in the
direction of current, then the thumb will
point in the direction of motion or force
acting on conductor.
(ii) As the direction of the force on a negatively charged electron will be opposite
to that of a positively charged alpha particle hence, an electron will experience a
force that pushes it towards the south when it passes through the same
magnetic field as that of alpha particle.
6. (a) What is ozone? How is it formed in the upper layers of the
Earth's atmosphere? How does ozone affect our ecosystem?
(b) “We do not clean a pond in the same manner as we do in an
aquarium." Give reason to justify this statement.
6. (a) What is ozone? How is it formed in the upper layers of the Earth's atmosphere? How
does ozone affect our ecosystem?
(b) “We do not clean a pond in the same manner as we do in an aquarium." Give reason to
justify this statement.
ANSWER: (a) Ozone is a molecule formed by three atoms of oxygen.
UV radiations split some molecular oxygen (O2) into free oxygen atoms (O + O).
These atoms then combine with molecular oxygen to form ozone.
Ozone layer shields the surface of the earth from damaging UV radiation of the
sun. / Depletion of ozone layer causes harmful effects on the organism.
(b)A pond is a natural ecosystem. It has decomposers whereas an aquarium is
an artificial ecosystem and does not contain decomposers. Therefore it needs
regular cleaning for proper functioning.
7. Write the name and the structural formula of the compound
formed when ethanol is heated at 443K with excess of conc.
H2SO4. State the role of conc. H2SO4 in this reaction. Write
chemical equation for the reaction.
7. Write the name and the structural formula of the compound formed when ethanol is
heated at 443K with excess of conc.
H2SO4. State the role of conc. H2SO4 in this reaction. Write chemical equation for the
reaction.
ANSWER: H2SO4 is a dehydrating agent. So, ethanol undergoes dehydration i.e., loses a
water molecule to form ethane.
8. (a) If the image formed by a mirror for all positions of the
object placed in front of it is always diminished, erect and
virtual, state the type of the mirror and also draw a ray diagram
to justify your answer. Write one use such mirrors are put to
and why.
(b) Define the radius of curvature of spherical mirrors. Find the
nature and focal length of a spherical mirror whose radius of
curvature is + 24 cm.
8. (a) If the image formed by a mirror for all positions of the object placed in front of it is
always diminished, erect and virtual, state the type of the mirror and also draw a ray diagram
to justify your answer. Write one use such mirrors are put to and why.
(b) Define the radius of curvature of spherical mirrors. Find the nature and focal length of a
spherical mirror whose radius of curvature is + 24 cm.
ANSWER:
(a) If the image formed by a mirror for all positions of the object placed in front of it is
always diminished, erect and virtual, then the type of the mirror is Convex.
Such mirrors are used as rear view mirrors in automobiles, as this type of mirror gives
erect, and a wider field of view of objects coming behind the automobile.
8. (a) If the image formed by a mirror for all positions of the object placed in front of it is
always diminished, erect and virtual, state the type of the mirror and also draw a ray diagram
to justify your answer. Write one use such mirrors are put to and why.
(b) Define the radius of curvature of spherical mirrors. Find the nature and focal length of a
spherical mirror whose radius of curvature is + 24 cm.
ANSWER:
(b) Radius of curvature of a spherical mirror is the distance between pole (P) and
centre of curvature, (C).
Given:
Radius of curvature, R =+24 cm
To find: Nature and focal length (f) of a spherical mirror.
Solution:
We know that radius of curvature is given as-
R=2f
then, f = R/2
Putting the value of R in the above equation, we get- f = 24/2 = +12 cm
Thus, the focal length of the spherical mirror is 12cm, and the plus sign implies that
the nature of the mirror is concave.
9. Which one of the two multicellular organisms Spirogyra and
Planaria reproduces by regeneration and why? Give an
example of any other organism which can also reproduce by
the same process.
9. Which one of the two multicellular organisms Spirogyra and
Planaria reproduces by regeneration and why? Give an example of
any other organism which can also reproduce by the same process.
ANSWER: Planarians can regenerate new
heads, tails, sides, or entire organisms from
small body fragments in a process taking days
to weeks. For example, a planarian split
lengthwise or crosswise will regenerate into
two separate individuals. Whereas in Spirogyra
asexual reproduction takes place by
fragmentation.
10. State the reason why carbon can neither form C4+ cations
nor C4- anions, but forms covalent compounds. Also state
reasons to explain why covalent compounds:
(i) are bad conductors of electricity?
(ii) have low melting and boiling points ?
10. State the reason why carbon can neither form C4+ cations nor C4- anions, but forms covalent
compounds. Also state reasons to explain why covalent compounds:
(i) are bad conductors of electricity?
(ii) have low melting and boiling points ?
ANSWER: The atomic number of Carbon is 6 with an electronic configuration of 2, 4.
Hence, carbon has 4 electrons in its valence shell. Carbon can lose or gain 4 electrons in
order to gain stability. It cannot gain four electrons as carbon atom having 6 protons is
very small to handle 10 electrons and it cannot donate electrons as it needs a lot of
energy to do so. Hence, it cannot form
C4+ cation or C4−anion and thus forms a covalent bond.
1. Covalent compounds are formed by sharing of electrons. They don't have a free
electron that is required for electricity transfer (electricity is the flow of free electrons),
thus they are bad conductors.
2. Covalent compounds have low melting and boiling points because they have weak
intermolecular forces between bonds. Hence, less energy/temperature is needed to break
the bonds.
11. An electric motor rated 1100 W is connected to 220 V mains.
Find:
(i)The current drawn from the mains,
(ii) Electric energy consumed if the motor is used for 5 hours
daily for 6 days.
(iii) Total cost of energy consumed if the rate of one unit is 5.
11. An electric motor rated 1100 W is connected to 220 V mains.
Find:(i)The current drawn from the mains, 5 A
(ii) Electric energy consumed if the motor is used for 5 hours daily for 6days. 33000 Wh
(iii) Total cost of energy consumed if the rate of one unit is 5. 7 165
ANSWER: We know,
power= 1100W
volt= 220V
a) Now, P=VI
1100 = 220×I
1100/220 = I
I = 5 ampere
b) E = Pt
E =1100×5×6
E = 33000Wh
E = 33 KWh
c) 1 KWh=1 unit
33 KWh=33 units
So, 1 unit = Rs.5
33 units = Rs.33×5
cost = Rs.165
12. (a) What happens when in a human female the egg released
by the ovary is not fertilised?
(b) Name one bacterial and one viral infection caused due to
unsafe sex.
12 (a) What happens when in a human female the egg released by the ovary is not
fertilised?
(b) Name one bacterial and one viral infection caused due to unsafe sex.
ANSWER: (a) If the egg is not fertilized, it lives for about one day and
the uterine lining formed to receive the fertilized egg slowly breaks
and comes out through the vagina as blood and mucous along with
unfertilized egg.
(b) Bacterial infection: Gonorrhoea/Syphilis. Viral infection: Warts /
AIDS.
13. (a) Distinguish between ‘roasting’ and ‘calcination’.Which of
these two is used for sulphide ores and why?
(b) Write a chemical equation to illustrate the use of aluminium
for joining cracked railway lines.
(c) Name the anode, the cathode and the electrolyte used in the
electrolytic refining of impure copper.
13. (a) Distinguish between ‘roasting’ and ‘calcination’.Which of these two is used for sulphide ores
and why?
(b) Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
(c) Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure
copper.
ANSWER: (a)Roasting: It is the process in which sulphide ores of the metals are converted into
oxides by heating them in the presence of excess air, For example zinc sulphide is converted
into zinc oxide by roasting.
Calcination: It is the process in which carbonates ores of the metals are decomposed into oxides
by heating them in the absence or limited air. For example, zinc carbonate is decomposed into
zinc oxide and carbon dioxide by calcination.
Out of roasting and calcination, only roasting is used for sulphide ores. This is because it is easier
to obtain metal from its oxide as compared to its sulphide.
13. (a) Distinguish between ‘roasting’ and ‘calcination’.Which of these two is used for sulphide ores
and why?
(b) Write a chemical equation to illustrate the use of aluminium for joining cracked railway lines.
(c) Name the anode, the cathode and the electrolyte used in the electrolytic refining of impure
copper.
ANSWER: (b)
(c) Anode - Impure Copper
Cathode - Strip of Pure Copper
Electrolyte - Acidified copper sulphate solution
14. A student holding a mirror in his hand, directed the
reflecting surface of the mirror towards the Sun. He then
directed the reflected light on to a sheet of paper held close to
the mirror.
(a) What should he do to burn the paper ?
(b) Which type of mirror does he have ?
14. A student holding a mirror in his hand, directed the reflecting surface of the mirror
towards the Sun. He then directed the reflected light on to a sheet of paper held close to
the mirror.
(a) What should he do to burn the paper ?
(b) Which type of mirror does he have ?
ANSWER: a) To burn the paper ‚student
should move (adjust )the mirror in such a
way that paper is positioned at the focus of
the mirror .
(b) He has concave mirror
15. Name the parts A, B and C shown in the following diagram
and state one function of each.
15 Name the parts A, B and C shown in the following diagram and state one function of
each.
ANSWER: A- Anther: It plays an important role in reproduction. It is responsible for
producing male gametophyte called pollen
B- Filament : It is a stalk-like structure that attaches to the base of the flower and
supports anther. It carries nutrients to anther. Long filaments help anther to
attract pollinating agents like bees and birds
C- Ovary: Ovary is the most important reproductive part of a flower. Ovary holds
ovules, which fertilizes to develop into a seed.
16. Write the molecular formula of the following carbon
compounds:
(i) Methane
(ii) Propane
(b) Carbon compounds have low melting and boiling points.
Why?
16. (a) Write the molecular formula of the following carbon compounds:
(i) Methane
(ii) Propane
(b) Carbon compounds have low melting and boiling points. Why?
ANSWER: (a) Molecular formula of the carbon compounds are:
Methane —
Propane —
(b) As carbon compounds are covalent compounds and forces of attraction between
these molecules is not very strong hence they have low melting and boiling points.
17. An object is placed at a distance of 30 cm from a concave
lens of focal length 15 cm. List four characteristics (nature,
position, etc.) of the image formed by the lens.
17. An object is placed at a distance of 30 cm from a concave lens of focal length 15 cm. List
four characteristics (nature, position, etc.) of the image formed by the lens.
ANSWER:
Given, object distance, u = - 30 cm and focal length, f = -15 cm
Characteristics of image :
(i) The image is formed at a distance of 10 cm from the concave lens on the left side.
(ii) Image formed is virtual.
(iii) Image formed is erect.
(iv) The size of the image formed is diminished.
18. (a) Why is there a difference in the rate of breathing
between aquatic organisms and terrestrial organisms? Explain.
(b) Draw a diagram of human respiratory system and label -
pharynx, trachea, lungs, diaphragm and alveolar sac on it.
18. (a) Why is there a difference in the rate of breathing between aquatic organisms and
terrestrial organisms? Explain.
(b) Draw a diagram of human respiratory system and label - pharynx, trachea, lungs,
diaphragm and alveolar sac on it.
ANSWER: (a) The rate of breathing in
aquatic organisms is much faster than in
terrestrial organisms because aquatic
animals breathe from the oxygen
dissolved in water. The dissolved oxygen
present in water bodies is less as
compared to the amount of oxygen
present in the atmosphere.
(b)
19. On heating blue coloured powder of copper (Il) nitrate in a
boiling tube, black copper oxide, O2 and a brown gas X is formed.
(a) Identify the type of reaction and the gas X.
(b) Write balanced chemical equation of the reaction.
(c) Write the pH range of aqueous solution of the gas X.
19. On heating blue coloured powder of copper (Il) nitrate in a boiling tube, black copper oxide, O2
and a brown gas X is formed.
(a) Identify the type of reaction and the gas X.
(b) Write balanced chemical equation of the reaction.
(c) Write the pH range of aqueous solution of the gas X.
ANSWER:
● The chemical reaction in which one reactant breaks down into two or more
products is known as a decomposition reaction(AB=A+B).
● The heating of Copper (II) nitrate, results in the loss of a water molecule and
anhydrous Copper (II) nitrate is formed.
● On further heating it gives a black residue of Copper oxide, a brown colour Nitrogen
dioxide gas, and colorless gas.
● The balanced chemical equation of the reaction is,
● Therefore, the brown gas is formed is Nitrogen dioxide respectively.
● Since Nitrogen dioxide is acidic, the pH range of Nitrogen dioxide is less than 7.
● Here, the Copper (II) decomposes to form copper oxide, nitrogen dioxide gas, and
oxygen gas as products, therefore, this is a decomposition reaction.
20. (a) Write the function of each of the following parts of
human eye:
(i) Cornea (ii) Iris (iii) Crystalline lens (iv) Ciliary muscles
(b) Why does the sun appear reddish early in the morning? Will
this phenomenon be observed by an astronaut on the Moon?
Give reason to justify your answer.
20. (a) Write the function of each of the following parts of human eye:
(i) Cornea (ii) Iris (iii) Crystalline lens (iv) Ciliary muscles
(b) Why does the sun appear reddish early in the morning? Will this phenomenon be
observed by an astronaut on the Moon? Give reason to justify your answer.
ANSWER:
(a) (i) Cornea: If refracts most of the light into eyes.
(ii) Iris: Gives colour to eyes, controls size of pupil.
(iii) Crystalline Lens: Focuses the image of the object on the retina.
(iv) Ciliary Muscles: Holds the eye lens and adjusts its focal length.
(b) At sunrise , the sun is located near horizon of earth and hence light travel a long
distance through earth atmosphere.The suspended atmospheric particle have
wavelength similar to blue light.When sunlight falls on atmosphere the blue light is
scattered out by these atmospheric particle the light reaches earth is predominantly
red.Hence,red light reaches our eyes, the sun and its surrounding appear reddish No,
same phenomenon will not occur on moon as there is no atmospheric to scatter light.
21. (a) What are hormones?
State one function of each of the following hormones:
(i) Thyroxine
(ii) Insulin
(b) Name the hormones secreted by the following endocrine
glands and specify one function of each :
(a) Thyroid (b) Pituitary (c) Pancreas
21.(a) What are hormones? State one function of each of the following hormones:
(i) Thyroxine (ii) Insulin
(b) Name the hormones secreted by the following endocrine glands and specify one
function of each : (i) Thyroid (ii) Pituitary (iii) Pancreas
ANSWER: (a) Hormones are the chemical substances which coordinate and
control the activities of living organisms and also their growth.
(i) Function of Thyroxine: This hormone regulates the metabolism of
carbohydrates and fats.
(ii) Function of insulin: This hormone helps in regulating sugar level in the
blood.
(b) (i) Thyroid secretes thyroxine hormone.
Function: Thyroxine regulates carbohydrate, protein and fat metabolism in
the body so as to provide the best balance for growth.
(ii) Pituitary secretes the growth hormone.
Function: Growth hormone regulates growth and development of the body.
(iii) Pancreas secretes insulin.
Function: helps in regulating blood sugar levels.
22. List the important products of the Chlor-alkali process. Write
one important use of each
22. List the important products of the Chlor-alkali process. Write one important use of each
ANSWER:
● There are three products that are produced in the Chlor-alkali process. These are
Sodium Hydroxide (NaOH), chlorine gas (Cl2), and hydrogen gas (H2)
Uses of sodium hydroxide:
● It is used for making soaps and detergents.
Uses of chlorine:
● It is used in the production of bleaching powder.
Uses of Hydrogen gas:
● It is used in the hydrogenation of oils to obtain vegetable ghee.
23. Study the following circuit and find:
(i) Effective resistance of the circuit
(ii) Current drawn from the battery
(iii) Potential difference across the
5 Ω resistor-
23. Study the following circuit and find:
(i) Effective resistance of the circuit
(ii) Current drawn from the battery
(iii) Potential difference across the 5 Ω resistor-
ANSWER:
24. (i) In a cross between violet flowered plants and white
flowered plants, state the characteristics of the plants obtained
in the F, progeny.
(ii) If the plants of F, progeny are self-pollinated, then what
would be observed in the plants of F, progeny?
(iii) If 100 plants are produced in F, progeny, then how many
plants will show the recessive trait?
24. (i) In a cross between violet flowered plants and white flowered plants, state the
characteristics of the plants obtained in the F, progeny.
(ii) If the plants of F, progeny are self-pollinated, then what would be observed in the plants
of F, progeny?
(iii) If 100 plants are produced in F, progeny, then how many plants will show the recessive
trait?
ANSWER: (i) In a cross between violet flowered (VV) plants and white flowered
(vv) plants, the plants obtained in the F1
progeny will bear purple flowers as
purple flower is dominant trait. Genotype of the F1
progeny will be
heterozygous (Vv).
(ii) If the plants of F1
progeny are self-pollinated, the plants in F2
generation will
be purple flowered and white flowered in a ratio of 3:1
(iii) If 100 plants are produced in F2
progeny, then 25 plants will show the
recessive trait.
25. When ethanol reacts with ethanoic acid in the presence of
conc. H2S4 a substance with fruity smell is produced. Answer
the following :
(i) State the class of compounds to which the fruity smelling
compounds belong. Write the chemical equation for the
reaction and write the chemical name of the product formed.
(ii) State the role of conc. H2SO4 in this reaction.
25. When ethanol reacts with ethanoic acid in the presence of conc. H2S4 a substance with fruity
smell is produced. Answer the following :
(i) State the class of compounds to which the fruity smelling compounds belong. Write the
chemical equation for the reaction and write the chemical name of the product formed.
(ii) State the role of conc. H2SO4 in this reaction.
ANSWER: (i) The fruity smelling compounds belong to the class of esters (Ethyl acetate).
The reaction of an alcohol with an acid to from ester and water is called as esterification.
CH3COOH (Ethanoic acid) + C2H5OH (Ethanol) → CH3COOC2H5 (Ethyl Acetate) +H2O
Here, the ester formed is Ethyl Acetate. It is a sweet smelling ester.
(ii) The concentrated H2SO4 acts as a catalyst and a dehydrating agent and helps in the
removal of water formed in the reaction between alcohol and carboxylic acid.
26. Draw the pattern of magnetic field lines produced around a
current carrying straight conductor passing perpendicularly
through a horizontal cardboard. State and apply right-hand
thumb rule to mark the direction of the field lines. How will the
strength of the magnetic field change when the point where
magnetic field is to be determined is moved away from the
straight conductor? Give reason to justify your answer.
26. Draw the pattern of magnetic field lines produced around a current carrying straight
conductor passing perpendicularly through a horizontal cardboard. State and apply
right-hand thumb rule to mark the direction of the field lines. How will the strength of the
magnetic field change when the point where magnetic field is to be determined is moved
away from the straight conductor? Give reason to justify your answer.
ANSWER: If a current carrying conductor is imagined to be held in your right hand such
that the thumb points along the direction of current, then the direction of the
wrapped fingers will give the direction of magnetic field lines.
27. Write down difference between Arteries and Veins.
27. Write down difference between Arteries and Veins.
ANSWER:
Arteries Veins
1. Arteries are bright red. 1. Veins are blue in color.
2. Arteries carry blood away from heart. 2. Veins carry blood towards the heart.
3. Arteries carry oxygenated blood 3. Veins carry deoxygenated blood.
4. Arteries are more muscular in comparative to veins 4. Veins are less muscular in comparative to arteries.
5. Arteries contain high blood pressure. 5. Veins contain low blood pressure
6. Arteries are divided into arterioles. 6. Veins are divided into venules.
28. The teacher while conducting practicals in the laboratory
divided the students into three groups and gave them various
solutions to find out their pH and classify them into acidic, basic
and neutral solutions.
Group A Lemon juice, vinegar, colourless aerated drink
Group B Tomato juice, coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
(a) For the solutions provided, which group is/are likely to have pH
value (i) less than 7, and (ii) greater than 7 ?
28. The teacher while conducting practicals in the laboratory divided the students into three
groups and gave them various solutions to find out their pH and classify them into acidic, basic and
neutral solutions.
Group A Lemon juice, vinegar, colourless aerated drink
Group B Tomato juice, coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
(a) For the solutions provided, which group is/are likely to have pH value (i) less than 7, and (ii)
greater than 7 ?
ANSWER:
(a) (i) Groups A and B- less than 7
(ii) Group C - greater than 7
29. The teacher while conducting practicals in the laboratory
divided the students into three groups and gave them various
solutions to find out their pH and classify them into acidic, basic
and neutral solutions. Group A Lemon juice, vinegar, colourless
aerated drink Group B Tomato juice, coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
b) List two ways of determining pH of a solution
29. The teacher while conducting practicals in the laboratory divided the students into three
groups and gave them various solutions to find out their pH and classify them into acidic, basic and
neutral solutions. Group A Lemon juice, vinegar, colourless aerated drink Group B Tomato juice,
coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
b) List two ways of determining pH of a solution
ANSWER:
(b) pH paper and universal indicator
30. The teacher while conducting practicals in the laboratory divided
the students into three groups and gave them various solutions to
find out their pH and classify them into acidic, basic and neutral
solutions. Group A Lemon juice, vinegar, colourless aerated drink
Group B Tomato juice, coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
(c) Explain, why the sour substances such as lemon juice are effective
in cleaning the tarnished copper vessels
OR
(c) pH has great importance in our daily life. Justify this statement
by giving two examples.
30. The teacher while conducting practicals in the laboratory divided the students into three
groups and gave them various solutions to find out their pH and classify them into acidic, basic and
neutral solutions. Group A Lemon juice, vinegar, colourless aerated drink Group B Tomato juice,
coffee, ginger juice
Group C Sodium hydroxide, sodium chloride, lime water
(c) Explain, why the sour substances such as lemon juice are effective in cleaning the tarnished
copper vessels
OR
(c) pH has great importance in our daily life. Justify this statement
by giving two examples.
ANSWER:
(c) • Copper vessel is tarnished due to formation of BasiC copper carbonate.
• Lemon juice being acidic react with copper oxide and the salt formed is washed away
OR
● An optimal pH is required for digestion.
● Change in pH can cause tooth decay.
● Animals and plants defend themselves through change in pH.
● Survival of aquatic life becomes difficult when pH of river water becomes low.
31. MnO2 + x HCL -> MnCl2 + y H2O + z Clz
In order to balance the above chemical equation, the values of x, y
and z respectively are:
(a) 6, 2, 2
(b) 4, 1, 2
(c) 4,2,1
(d) 2, 2, 1
32. Select washing soda from the following:
(a) NaHCO3
(b) Na2CO3.5H,0
(c) Na2CO3.10H20
(d) NaOH
33. The emission of brown fumes in the given
experimental set-up is due to:
(a) thermal decomposition of lead nitrate which
produces brown fumes of nitrogen dioxide.
(b) thermal decomposition of lead nitrate which
produces brown fumes of lead oxide.
(c) oxidation of lead nitrate forming lead oxide
and nitrogen dioxide.
(d) oxidation of lead nitrate forming lead oxide
and oxygen.
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