Chapter 9, Problem 2STP

Interpretation Introduction

Interpretation: From the given set ionic compounds have to be identified.

Concept Introduction: Ionic compounds are those in which positively and negatively charged ions are held together by the electrostatic force of attraction. They separate into the respective ions when dissolved in water.

Answer to Problem 2STP

Among the given compounds ${\text{CaSO}}_{\text{4}}\text{,}{\text{NH}}_{\text{4}}{\text{NO}}_{\text{3}}\text{and}\text{CaS}$ are ionic compounds. Hence, option D is the correct answer.

Explanation of Solution

The compounds I, III, and IV are ${\text{CaSO}}_{\text{4}}\text{,}{\text{NH}}_{\text{4}}{\text{NO}}_{\text{3}}$ and $\text{CaS}$ . They are consisting of ${\text{Ca}}^{\text{2+}}\text{and}{\text{SO}}_{\text{4}}{}^{2-}$ , ${\text{NH}}_{\text{4}}{}^{+}\text{and}{\text{NO}}_{\text{3}}{}^{-}\text{,}\text{and}$ ${\text{Ca}}^{\text{2+}}\text{and}{\text{S}}^{2-}$ ions respectively. They all are ionic compounds.

Thus, option (D) is correct.

Conclusion

The compound ${\text{N}}_{\text{2}}{\text{O}}_{\text{4}}$ is covalent because nitrogen and oxygen both are non-metals. Thus, options (A), (B), and (C) are incorrect.