Question

In which case, purity of the substance is $ 100\% $ ?
(A) $ 1{\text{ mole of CaC}}{{\text{O}}_3}{\text{ gave 11}}{\text{.2L C}}{{\text{O}}_2}{\text{ (at STP)}} $
(B) $ 1{\text{ mole of MgC}}{{\text{O}}_3}{\text{ gave 40}}{\text{.0g MgO}} $
(C) $ 1{\text{ mole of NaHC}}{{\text{O}}_3}{\text{ gave 4g }}{{\text{H}}_2}{\text{O }} $
(D) $ 1{\text{ mole of Ca(HC}}{{\text{O}}_3}{{\text{)}}_2}{\text{ gave 1 mole C}}{{\text{O}}_2}{\text{ }} $

Answer 1

Hint :The absence of impurities or types of matter other than the substance itself is called purity. There are many tests to check the purity of a substance. To solve this problem, we have to write the chemical reactions and find mole ratios.

Complete Step By Step Answer:
Assume that all the given compounds are $ 100\% $ pure. So, $ 1{\text{ mole of CaC}}{{\text{O}}_3} $ should give $ {\text{22}}{\text{.4L C}}{{\text{O}}_2}{\text{ (at STP)}} $ . This is determined from the stoichiometric ratio of moles of reactant to moles of carbon dioxide. Write a chemical equation and find the ratio of moles of calcium carbonate to carbon dioxide. $ 1{\text{ mole of MgC}}{{\text{O}}_3} $ should give $ 40.0{\text{ g MgO}} $ . $ {\text{22}}{\text{.4L C}}{{\text{O}}_2}{\text{ (at STP)}} $ . This is determined from the stoichiometric ratio of moles of reactant to moles of magnesium oxide. Write a chemical equation and find the ratio of moles of magnesium carbonate to magnesium oxide. $ 1{\text{ mole of NaHC}}{{\text{O}}_3} $ should give $ 9{\text{ g }}{{\text{H}}_2}{\text{O}} $ . This is determined from the stoichiometric ratio of moles of reactant to moles of water. Write a chemical equation and find the ratio of moles of $ NaHC{O_3} $ to water. $ 1{\text{ mole of Ca(HC}}{{\text{O}}_3}{)_2} $ should give $ 2{\text{ moles C}}{{\text{O}}_2} $ . This is determined from the stoichiometric ratio of moles of reactant to moles of carbon dioxide. Write a chemical equation and find the ratio of moles of $ {\text{Ca(HC}}{{\text{O}}_3}{)_2} $ to carbon dioxide.
Therefore, option B is the correct answer.

Note :
Percentage purity is calculated by dividing the mass of the pure chemical by the total mass of the sample given and then multiplying the result by $ 100 $ . The percent yield is defined as the ratio of the actual yield to the theoretical yield expressed in the percentage form.