Question

Which of these products is a pure substance:
Co2 + 2NaoH ---- No2Co3 + H2o
HCl + NaoH --- NaCl +H2o
2Ki + pbNo32 --- pbi + 2KNo3
Caco3 --- Cao + Co2

Answer 1

So, products of reaction $2\mathrm{NaOH} + \mathrm{CO}_2 \rightarrow \mathrm{Na}_2\mathrm{CO}_3 + \mathrm{H}_2\mathrm{O}$ is mixture or solution of $\mathrm{Na}_2\mathrm{CO}_3 + \mathrm{H}_2\mathrm{O}$ , so it is not pure substance.

Products of reaction $\mathrm{NaOH} + \mathrm{HCl} \rightarrow \mathrm{NaCl} + \mathrm{H}_2\mathrm{O}$ is mixture or solution of $\mathrm{NaCl} + \mathrm{H}_2\mathrm{O}$ , so it is not pure substance.

Products of reaction $2\mathrm{KI} + \mathrm{Pb}(\mathrm{NO}_3)_2 \rightarrow 2\mathrm{KNO}_3 + \mathrm{PbI}_2$ is not mixture of $\mathrm{KNO}_3$ and $\mathrm{PbI}_2$ , because $\mathrm{PbI}_2$ is precipitate and it is pure substance.

Products of reaction $\mathrm{CaCO_3} \rightarrow \mathrm{CaO} + \mathrm{CO_2}$ is not mixture, because $\mathrm{CaO}$ is solid and $\mathrm{CO_2}$ gas, so there are two pure substances as products.