Q1: The most commonly used indicator in
laboratory is
(a) Methyl Orange
(b) Litmus
(c) Phenolphtalein
(d) Universal Indicator
Answer: Universal Indicator
Q2: Olfactory indicators are:
(a) Clove
(b) Turmeric
(c) Soap
(d) Rose Petals
Answer: (a) Clove
Q3: An element common to all acids is
(a) Chlorine
(b) Nitrogen
(c) Oxygen
(d) Hydrogen
Answer: (d) Hydrogen
Q4: Metal carbonate on reaction with dilute acid
release
(a) CO 2
(b) CO
(c) H 2 O
(d) H 2
Answer: (a) CO2
Q5 ln general, salts
(a) are ionic compounds
(b) contain hydrogen ions
(c) contain hydroxide ions
(d) turn litmus red
Answer: (a) are ionic compounds
Q6: On passing excess of CO 2 gas in an aqueous
solution of calcium carbonate, milkiness of the
solution
(a) persists
(b) fades
(c) deepens
(d) disappears
Answer: (b) fades
Q7 When magnesium and hydrochloric
acid react, they produce
(a) Oxygen and magnesium chloride
(b) Chlorine and magnesium oxide
(c) Hydrogen and magnesium chloride
(d) Hydrogen and magnesium oxide
Answer: (c) Hydrogen and magnesium chloride
Q8: Dissolution of acid or base in water is
(a) Exothermic
(b) Endothermic
(c) Violent
(d) None of these
Answer: (a) Exothermic
Q9: Water contains more H+ ions than OH- ions. In
this case, water is
(a) neutral
(b) basic
(c) acidic
(d) cannot say.
Answer: (c) acidic
Q10: When an acid reacts with a base what
compounds are formed?
(a) water only
(b) metal oxides only
(c) a salt only
(d) a salt and water
Answer: (d) a salt and water
Q11: Which of the following is a property of an
acid?(a) slippery feel
(b) non-reactive
(c) sour taste
(d) strong color
Answer: (c) sour taste
Q12: On diluting an acid concentration of H+ per
unit volume
(a) increases
(b) decreases
(c) remains unaffected
(d) depends on type of acid used.
Answer: (b) decreases
Q13: What is pH?
(a) the positive logarithm of the hydroxide ion
concentration
(b) the positive logarithm of the hydrogen ion
concentration
(c) the negative logarithm of the hydroxide ion
concentration
(d) the negative logarithm of the hydrogen ion
concentration
Answer: (d) the negative logarithm of the hydrogen ion
concentration
Q14: Tartaric acid is the constituent of
(a) bleaching powder
(b) baking powder
(c) washing powder
(d) plaster of paris
Answer: (b) baking powder
Q15: A solution turns blue litmus red. Its pH value
is likely to be
(a) 4
(b) 7
(c) 9
(d) 12
Answer: (a) 4
Q16: What is the name of H 2SO 3 ?
(a) Sulphuric Acid
(b) Sulphurous Acid
(c) Sulphite Acid
(d) Hydrogen Sulphide.
Answer: (b) Sulphurous Acid
Q17: Which gas is produced by reaction of base
with metal ?
(a) Carbon dioxide
(b) Dioxygen
(c) Dihydrogen
(d) Dinitrogen
Answer: (c) Dihydrogen
Q18: Acid + Metal-oxide → ?
(a) Base + Water
(b) Salt + Water
(c) Base + Salt
(d) Metal + Salt
Answer: (b) Salt + Water
Q19: Which of the following is a weak acid?
(a) Hydrochloric Acid
(b) Nitric Acid
(c) Acetic Acid
(d) Sulphuric Acid
Answer: (c) Acetic Acid
Q20: An indicator is what type of compound?
(a) reducing agent
(b) strong base or acid
(c) weak base or acid
(d) salt
Answer: (c) weak base or acid
Q21: Which of the following is strong acid ?
(a) Acetic acid
(b) Citric acid
(c) Nitric acid
(d) Oxalic acid
Answer: (c) Nitric acid
Q22: Name the organic acid present in tomato
(a) Tartaric Acid
(b) Malic Acid
(c) Lactic Acid
(d) Oxalic Acid
Answer: (d) Oxalic Acid
Q23: Fill in the blanks.
(a) Turmeric, clove, rose petals are ______ _____ .
(b) Acids ______ _______ bases to form ________ and
water.
(c) The term pH was coined by _______ .
(d) Turmeric turns _____ _______ in basic medium.
(e) ________ ________ is used in softening water.
(f) String acids show ______ ionisation while weak acids
show _______ ionisation.
(g) Calcium Sulphate hemihydrate is popularly known as
_____ ___ _____.
(h) Acids contain the hydrogen (H + ) as the only ______ _
______.
(i) Bases contain the Oxide (O 2- ) or hydroxide (OH -)
radical as the only _______ radical.
Answer:
(a) Olfactory indicators
(b) reacts with, salt
(c) Sørensen
(d) deep brown
(e) Washing Soda
(f) more, less
(g) Plaster of Paris
(h) positive radical
(i) negative
Q24: List the organic acid present in the following
objects:
(a) Citrus Fruits (lemon, orange)
(b) Sting of bees and ants
(c) Rancid butter
(d) Tamarind, grapes, apples
(e) Apples
(f) Gastric juice
(g) Vinegar
(h) Fats
(i) Urine
(j) Sour milk, curd
Answer:
(a) Citrus Fruits (lemon, orange): Citric acid
(b) Sting of bees and ants: Formic acid
(c) Rancid butter: Butryic acid
(d) Tamarind, grapes, apples : Tartaric acid
(e) Apples: Malic acid
(f) Gastric juice: Hydrochloric acid
(g) Vinegar: Acetic acid
(h) Fats: stearic Acid
(i) Urine: Uric Acid
(j) Sour milk, curd: Lactic acid
Q25: State true (✓) or false (✗ )
(a) Heat is evolved during ionisation.
(b) Solution of glucose in water produces ions.
(c) Dry ammonia has no effect on litmus paper.
(d) Higher is the concentration of H(aq), lower is the
pH value.
(e) The concentration of aqueous solutions of acid, base
and salt are generally expressed in molarity.
(f) pH of a solution can vary from 0-14.
(g) HC1 is a weak acid.
(h) NaOH is a strong base.
(i) Curd is alkaline in comparison to fresh milk.
(j) pH = + log10[(H 3 O -]
(k) Distilled water does not conduct electricity.
(l) Analgesics helps to relieve acidity.
Answer:
(a) Heat is evolved during ionisation. - True(✓)
(b) Solution of glucose in water produces ions. False (✗)
(c) Dry ammonia has no effect on litmus paper. (True)
✓
(d) Higher is the concentration of H(aq), lower is the
pH value. True(✓)
(e) The concentration of aqueous solutions of acid, base
and salt are generally expressed in molarity.True(✓)
(f) pH of a solution can vary from 0-14. True(✓)
(g) HC1 is a weak acid. False (✗)
(h) NaOH is a strong base. True(✓)
(i) Curd is alkaline in comparison to fresh milk. False (✗)
(j) pH = + log10[(H 3 O -] False (✗)
(k) Distilled water does not conduct electricity. True(✓)
(l) Analgesics helps to relieve acidity. False (✗)
Q26: Identify which of the following chemical
formulas is acid, base or salt. Write their
corresponding chemical names also.
(a) HCl
(b) NaOH
(c) NaCl
(d) Ca(NO 3) 2
(e) Ca(OH) 2
(f) HNO3
(g) NH 4 OH
(h) (NH 4 )2 SO 4
(i) CuO
(j) H 2SO 4
(k) CuCO 3
(l) H 2CO 3
(m) MgO
(n) Mg3 (PO 4) 2
Answer:
(a) HCl - Hydrochloric Acid
(b) NaOH - Sodium Hydroxide - Base
(c) NaCl - Sodium Chloride - Salt
(d) Ca(NO 3) 2 - Calcium Nitrate - Salt
(e) Ca(OH) 2 - Calcium Hydroxide
(f) HNO3 - Nitric Acid
(g) NH 4 OH - Ammonium hydroxide - Base
(h) (NH 4 )2 SO 4 - Ammonium sulphate - Salt
(i) CuO - Copper Oxide
(j) H 2SO 4 - Sulphuric Acid
(k) CuCO 3 - Copper Carbonate
(l) H 2CO 3 - Carbonic acid
(m) MgO - Magnesium Oxide
(n) Mg3 (PO 4) 2 - Magnesium Phosphate
Q27: You have been provided with three test tubes.
One of them contains distilled water and the other
two contain an acidic solution and a basic solution,
respectively. If you are given only red litmus paper,
how will you identify the contents of each test
tube?
Answer: The colour of red litmus paper changes to blue
indicates that the chemical is a base. If there is no
change in colour, then it is either acidic or neutral. We
can easily identify a base.
1. Mark the three test tubes as A, B, and C.
2. Take a drop of the solution A and put it on the red
litmus paper. Repeat the same process iwth solution B
and C.
3. If any of them changes colour to blue, then it is a
base.And remaining two are acid and neutral.
4. Now take a drop from the identified base and mix it
with a drop taken from the remaining two solutions
separately.
5. Check the drops of the mixtures on red litmus paper.
6. If the colour of red litmus turns blue, then the second
solution is neutral. If it does not change colour, then
the second solution is acid. This is because acidic and
basic solutions neutralize each other.
Q28: Why should curd and sour substances not be
kept in brass and copper vessels?
Answer: Curd and sour substances are acidic by nature.
e.g. curd contains lactic acid. When these substances
are kept in metal containers like brass and copper,
metal react with acid and liberate hydrogen gas and
other harmful substances, which may spoil these
substances.
Q29: Why vinegar is used in pickling?
Answer: Vinegar contains an organic acid called acetic
acid (CH 3COOH) which prevents the growth of micro
organisms. Therefore it is used in pickling.
Q30: Why phenolphthalein is considered acid base
indicator?
Answer: It is because phenolphthalein turns pink in
basic solution whereas it remains unaffected in acid or
neutral solutions. It is able to differentiate between acid
(colouless) and base (pink colour).
Q31 Which gas is usually liberated when
an acid reacts with a metal? Illustrate with an
example. How will you test for the presence of this
gas?
Answer: Hydrogen gas is liberated when an acid reacts
with a metal.
Take few pieces of zinc (Zn) granules in a delivery tube.
Add 5ml of hydrochloric acid (HCl). White fumes will
rise. Pass the gas to a soap solution or collect it in a
balloon (as shown in the following video). The gas
collected is Hydrogen gas. Since H2 gas has lower
density as compared to air, the balloon will float in air.
Zn (s) + 2HCl (aq) → ZnCl2 (s) + H 2 (g)
You can test the evolved hydrogen gas by its burning
with a pop sound when a candle is brought near the
balloon (or soap bubbles).
Q32 Metal compound A reacts with dilute
hydrochloric acid to produce effervescence. The gas
evolved extinguishes a burning candle. Write a
balanced chemical equation for the reaction if one
of the compounds formed is calcium chloride.
Answer: Since CO2 gas is liberated and the salt obtain
has metal Ca, it implies the reactant metal compound
shall be a carbonate i.e. CaCO3
The chemical equation is:
CaCO3 (s) + 2HCl (aq) → CaCl 2 (s) + CO2 (g) +
H2 O (l)
Calcium Carbonate + Hydrochloric Acid → Calcium
Chloride + Carbon Dioxide + Water
Q33 Why do HCl, HNO 3 , etc., show acidic
characters in aqueous solutions while solutions of
compounds like alcohol and glucose do not show
acidic character?
Answer: As aqueous solution, HCl and HNO 3 dissociate
into H + and Hydronium (H 3 O+ ) ions.
HCl (aq) → H + + Cl -
H + + H2 O → H 3O +
Although glucose and alcohol contain hydrogen, as
aqueous solution, they do not dissociate into ions and
do not exhibit acidic character.
Q34(NCERT): Why does an aqueous solution of an
acid conduct electricity?
Answer: The aqueous solution of an acid contains H +
and Hydronium (H 3O + ) ions. Since ions carry extra
charge and are able to conduct electricity.
Q35: Why should acids be handled with care?
Answer: Acids have burning effect on our skin. They are
corrosive to living beings. Proper care must be taken
while handling acids in laboratory.
Q36: Why does dry HCl gas not change the colour of
dry litmus paper
Answer: Dry HCl gas does not form H + ions. It does not
show its acidic character. When in the aqueous
solution, an acid ionizes to form H+ ions. In this case,
neither HCl is in an aqueous form nor the litmus paper
is wet, therefore, the colour of the litmus paper does
not change.
Q37: While diluting an acid, why is it recommended
that the acid should be added to water and not
water to the acid?
Answer: When diluting, the acid should always be added
slowly to water and in small amounts. Adding water to
an acid is an exothermic process, it can cause
uncontrolled boiling and splashing. That's why it is
recommended that the acid should be added to water
and not water to the acid.
Q38: What is an amphoteric substance?
Answer: A substance is said to be amphoteric if it can
behave either as an acid or as a
base. Water is the most common amphoteric substance.
Q39: On the basis of origin, how acids are
classified?
Answer: On the basis of origin, acids are classified as:
1. Organic acids
2. Inorganic or Mineral acids
Q40: What are organic acids? Give two examples
Answer: Acids obtained from living beings (plants and
animals) are called organic acid.
e.g. citric acid present in fruits like lemon, oxalic acid in
tomato etc.
Q41: What are mineral acids? Give two examples
Answer: In general acids obtained from minerals or
non-living things are called mineral or inorganic acids.
Examples are:
Sulphuric acid (H 2 SO4 )
Nitric Acid (HNO 3)
Q42: What is the chemical name of Bleaching
powder? How it is prepared? List its uses.
Answer:
Chemical Name of Bleaching Powder: Calcium
Oxychloride
Chemical Formula: CaOCl 2
Preparation: It is prepared by passing chlorine gas
through dry slaked lime.
Ca(OH) 2 + Cl 2 → CaOCl 2 + H 2O
Slaked Lime + Chlorine → Bleaching Powder +
Water
Uses:
1. As bleaching agent in textile industry.
2. As disinfectant in water purification.
3. In paper industry to bleach wood pulp
Q43: Which acid is used in Cola to give it a biting
sharp taste?
Answer: Phosphoric acid.
Q44: What is gypsum?
Answer: Plaster of Paris reacts with water to give a hard
mass called gypsum.
(CaSO 4 )2 . H2 O (s) + 3 H 2O (l) →
2CaSO 4 .2H 2 O (s)
Plaster for Paris + Water → Gypsum
Q45 Define Dilution.
Answer: Mixing an acid or base with water results in
decrease in the concentration of ions (H 3 O + /OH –) per
unit volume. Such a process is called dilution and the
acid or the base is said to be diluted.
Q46 Tooth enamel is one of the
hardest substance in our body. How does it undergo
damage due to the eating of chocolates and
sweets? What should we do to prevent it?
or
Q: Why does tooth decay start when the pH of the
mouth is lower than 5.5?
Answer: Tooth decay starts when the pH of the mouth
is lower than 5.5. Tooth enamel, made up of calcium
phosphate is the hardest substance in the body. It does
not dissolve in water, but is corroded when the pH in
the mouth is below 5.5. Bacteria present in the mouth
produce acids by degradation of sugar (due to
chocolates and sweets) and food particles remaining in
the mouth after eating. The best way to prevent this is
to clean the mouth after eating food.
Using toothpastes, which are generally basic, for
cleaning the teeth can neutralise the excess acid and
prevent tooth decay.
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