Chapter U4, Problem 5STP

Interpretation Introduction

Interpretation:

The chemical reaction that correctly matches type of reaction with balanced chemical reaction needs to be determined.

Concept introduction:

Chemical equation is written in such a way that the symbolic representation of reaction represents the reaction taking place in the system. The reactants are written on the left-hand side and the products are written on the right-hand side of the equation and are separated by an arrow, two or more reactants and products are separated by “+”.

The reactions for which the number of atoms of each element in the reactant and in the product side is same, are said to be balanced chemical reactions.

Answer to Problem 5STP

The correct option is (c):

decomposition:

${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}\text{(s)}\to {\text{Na}}_{\text{2}}{\text{O(s) + CO}}_2\text{(g)}$

Explanation of Solution

Reason for correct option:

In decomposition reactions, the product gets break down into two or more simpler products.

The given decomposition reaction is:

${\text{Na}}_{\text{2}}{\text{CO}}_{\text{3}}\text{(s)}\to {\text{Na}}_{\text{2}}{\text{O(s) + CO}}_2\text{(g)}$

As in this reaction, a single reactant, sodium carbonate breaks down to give two products, sodium oxide and carbon dioxide so, the reaction type is correct that is decomposition reaction.

Hence, the correct option is (c).

Conclusion

Reason for incorrect option(s):

• In single exchange reactions, the element(s) in a compound is replaced by the other element(s) in other words the reacting element switches place with an element in the other reacting compound.
• In double exchange reactions, the positive ions that is cations and the negative ions that is anions of the two reactants, on reacting two compounds (reactants) switch places and results in the formation of two new compounds (products).
• In combination reaction, formation of a product takes place by reacting two or more compounds or elements.

(a) Single exchange:

${\text{NaCl(aq) + AgNO}}_{\text{3}}\text{(aq)}\to {\text{Na}}_{\text{2}}{\text{NO}}_{\text{3}}\text{(aq) + AgCl(aq)}$

Since, in the above reaction the cations and anions of both the reactants switch places resulting in the formation of two new compounds, so the reaction type is incorrect and the correct type is double exchange reaction.

(b) Double exchange:

${\text{AlBr}}_3{\text{(aq) + 3Cl}}_2\text{(g)}\to 2{\text{AlCl}}_{\text{3}}{\text{(aq) + 3Br}}_2\text{(g)}$

Since, in the above reaction element in a compound is replaced by the other element so, the reaction type is incorrect and the correct type is single exchange reaction.

(c) Combination:

${\text{2PbSe(s) + O}}_2\text{(g)}\to 2\text{PbO(s) + 2Se(s)}$

Since, in the above reaction element in a compound is replaced by the other element so, the reaction type is incorrect and the correct type is single exchange reaction.