ACIDS, BASES
AND SALTS
2
EXERCISE 2.1
Topics:
Chemical properties of acids and bases.
2 MARKS
1.
A solution of substance ‘X’ is used for white washing –
(a) Name the substance ‘X’ and write its formula
(b) Express the reaction of ‘X’ with water in the form of a balanced chemical equation.
(2013, 2014)
Ans. (a) X → quick lime
Formula → CaO
(b) CaO + H2O→ Ca (OH)2
2.
What is a neutralisation reaction ? Give one example.
(2013)
Ans. When acid reacts with base to form salt and water it is called neutralisation reaction.
NaOH + HCl → NaCl + H2O
Base
3.
Write chemical equations that shows aluminium oxide reacts with acids as well as
base.
(2011, 2013)
Acid
salt
water
Ans. Al2O3 + 6HCl → 2AlCl3 + 3H2O
Al2O3 + 2NaOH → 2NaAlO2 + H2O
4.
A substance X, which is an oxide of a metal 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 also write the equation for its chemical
reactions with water.
(2012, 2014)
Ans. Calcium oxide.
CaO(s) + H2O(l) → Ca(OH)2(aq)
5.
A student dropped few pieces of marble in dilute HCl contained in a test tube. The
evolved gas was passed through lime water. TEACHERS FORUM
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(i) What change would be observed in lime water ?
(ii) Write balanced chemical equation for the above change.
(2013)
Ans. (i) lime water turns milky.
(ii) Ca(OH)2 + CO2 → Ca CO3 + H2 O
lime water
calcium carbonate
3 MARKS
6.
Illustrate any three chemical properties of acids with examples.
(2014)
Ans. (i)
Acids react with metals to produce salt and hydeogen gas.
Eg: H2SO4 + Zn → ZnSO4 + H2
(ii)
Acids react with metal carbonate to produce salt, carbon dioxide and water.
Eg: Na2CO3 + 2 HCl → 2 NaCl + H2O + CO2
(iii) Acids react with bases to produce salt and water.
NaCl + HCl → NaCl + H2O
7.A solution of a substance ‘ X ‘ is used for testing carbon dioxide. Identify ‘X’. What will
be its reaction with carbon dioxide ? Write balanced equation for the reaction ?
Ans.X → Ca(OH)2 or Calcium hydroxide
(2010, 2012)
(lime water)
Ca(OH)2 + CO2 → CaCO3 + H2O
CO2 gas turns lime water milky due to formation of insoluble Calcium Carbonate
5 MARKS
8.
(a) You have been provided with three test tubes. One of them contains distilled
water and the other two contains an acidic solution and a base solution
respectively. If you have only red litmus paper how will you identify the contents
of each test tube ?
(b) List two differences between an acid and a base on the basis of their chemical
properties. (2010, 2011, 2012)
Ans. (a) Dip the red litmus in each of the three test tubes and note the changes in colour.
If purple colour – Distilled water
If blue colour – Basic solution
If red colour (No change in colour) – Acidic solution
TEACHERS FORUM
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