YASH CLASSES
ACIDS , BASES AND SALTS
Q. 1. A solution turns red
litmus blue, its pH is likely to be
(a)
1 (b) 4 (c) 5 (d) 10
Ans. (d) pH = 10.
Q. 2.
A solution reacts with crushed egg-shells to give a gas
that turns lime- water milky. The solution
contains
(a) NaCl (b) HCI (c) LICI (l) KCl
Ans. (b) HCl.
Q. 3. 10 mL of a solution of
NaOH is found to be completely neutralized by 8 mL of a given solution of HCl.
If we take 20 mL of the same solution of NaOH , the amount HCl solution (the
same solution as before) required to neutralize it will be
(a) 4 ml (b) 8ml (c) 12 ml (d) 16 ml
Ans. (d) 16 ml
Q. 4. Which one of the following
types of medicines is used for
treating indigestion?
(a) Antibiotic (b) Analgesic (c)
Antacid (d) Antiseptic.
Ans. (c)
Antacid.
Q. 5. Write word equations and then balanced
equations for the
reaction taking place when:
(a)
dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts
with magnesium ribbon.
(c) dilute sulphuric acid reacts with aluminum powder.
(d) dilute hydrochloric acid
reacts with iron filings.
Ans. (a) Zinc+ dil. sulphuric
acid → Zinc sulphate + Hydrogen
Zn +
H₂SO₄ →
ZnSO4 + H₂
(b)Magnesium ribbon +dil.
hydrochloric acid →
Magnesium chloride + Hydrogen
Mg + 2HCl → MgCl2 + H₂
(c) Aluminium powder + dil. sulphuric acid →
Aluminum
sulphate + Hydrogen
2Al + 3H2SO4
→ Al2(SO4)3 + 3 H₂
(d) Dilute hydrochloric acid + Iron
filings → Iron chloride + Hydrogen
2Fe + 6HCl → 2FeCl3+ 3H2
Q. 6. Compounds such as alcohols
and glucose also contain hydrogen but are not categorised as acids. Describe an
activity to prove it.
Ans. Take solutions of alcohols, glucose in a beaker. Take a
cork and fix two nails on the cork up to the end. Keep this cork in the beaker.
Connect the nails to two terminals of a 6-volt battery through a bulb and a
switch. Switch on the current. You will see that bulb does not glow or the
current does not pass through the circuit. This means no ions or H ions are
present in the solution. This shows that alcohols and glucose are not acids.
Q. 7. Why does distilled water
not conduct electricity, whereas rain
water does?
Ans. Rain water
contains ions of acids and so it conducts electricity
whereas
there are no ions in distilled water.
Q. 8. Why do acids not show
acidic behavior in the absence of water?
Ans. Acids in water give hydronium ions which are
responsible for their acidic behavior but in the absence of water acids do not
generate hydronium ions and thus do not show acidic behavior.
Q. 9. Five solutions A, B, C, D
and E when 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. (a)
D (b)
C (c)
B (d) A (e) E
pH values in
increasing order of hydrogen ion concentration:
11 < 9 < 7
< 4 < 1.
Q. 10. Equal lengths of
magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCI) is
added to test tube A, while acetic acid (CH,COOH) is added to test tube B.
Amount and concentration taken for both the acids are same. In which test tube
will the fizzing occur more vigorously and why?
Ans. Fizzing will
occur more vigorously in test A containing hydrochloric acid. This is because
hydrochloric acid is stronger acid than acetic acid and reaction between
magnesium ribbon and HCl is faster than
between Mg and acetic acid.
Q. 11. Fresh milk has a pH of 6.
How do you think the pH will change as
it turns into curd? Explain your answer.
Ans. pH of milk
falls below 6 as it turns into curd due to the formation
of lactic acid
during this process.
Q. 12. A milkman adds a very
small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk
from 6 to slightly
alkaline?
(b) Why
does this milk take a long time to set as curd?
Ans. (a) The milkman adds a
little baking soda to fresh milk to make it
slightly alkaline so that it can be
preserved for a longer time.
(b) Initially lactic acid formed is used up to
neutralize the base i.e., baking soda and when more lactic acid is formed, the
milk seta as curd.
Q. 13. Plaster of Paris should
be stored in a moisture-proof container.
Explain why?
Ans. Plaster of Paris is calcium sulphate hemihydrate (CaSO4.
½ H₂O).
On exposure to
moisture it absorbs moisture and becomes gypsum
(CaSO4.2H₂O)
which does not have the required setting property.
Q. 14. What is a neutralisation
reaction? Give two examples.
Ans. The reaction
between an acid and a base to give salt and water
is known as a neutralization reaction.
Examples:
Acid + Base → Salt + Water
(1) HCI + NaOH
(Acid) →
NaCl (Salt) + H₂O
Hydrochloric (Base)
Sodium ( Sodium Water
acid hydroxide chloride)
(ii) CH3COOH + NaOH
→ CH3COONa + H₂O
(Acid) (Base) (Salt)
Q. 15. Give two important uses
of washing soda and baking soda.
Ans. Uses of baking soda:
(i) It is used
in bakery.
(ii) It is used
in soda-acid fire extinguishers.
Uses of washing soda:
(i) It is used
in the manufacture of glass, soap and paper.
(ii)
It is used for removing permanent hardness of water.