Chapter 01 Chemical Reactions and Equations Questions-02
QUESTIONS
1. A solution of a substance ’ $X$ ’ is used for whitewashing.
(i) Name the substance ’ $X$ ’ and write its formula.
(ii) Write the reaction of the substance ’ $X$ ’ named in (i) above with water.
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Answer The substance ’ $X$ ’ is calcium oxide. Its chemical formula is $CaO$. Calcium oxide reacts vigorously with water to form calcium hydroxide (slaked lime).
$CaO _{(s)}+H_2 O _{(l)} \longrightarrow Ca(OH) _{2(a q)}$
Calcium oxide Water Calcium hydroxide
(Quick lime)
(Slaked lime)
2. Why is the amount of gas collected in one of the test tubes in Activity 1.7 double of the amount collected in the other? Name this gas.
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Answer
Water (H2O) contains two parts hydrogen and one part oxygen. Therefore, the amount of hydrogen and oxygen produced during electrolysis of water is in a 2:1 ratio. During electrolysis, since hydrogen goes to one test tube and oxygen goes to another, the amount of gas collected in one of the test tubes is double of the amount collected in the other.
