When a mixture of white solids Z, is treated with an excess of dilute hydrochloric acid, a colorless gas is evolved and some, (but not all) of the mixture dissolve.

Correct answer: B. BaSO4 and CaCO3

A. Ba(NO3)2 and Ca(OH)2
B. BaSO4 and CaCO3
C. CaCO3 and MgSO4
D. Ca(OH)2 and MgCO3

Explanation

The reaction between dilute hydrochloric acid and BaSO4 is: BaSO4 + 2HCl → BaCl2 + SO2 + H2O BaSO4 is insoluble in dilute hydrochloric acid, so it does not dissolve. SO2 gas is evolved. The reaction between dilute hydrochloric acid and CaCO3 is: CaCO3 + 2HCl → CaCl2 + CO2 + H2O CaCO3 is soluble in dilute hydrochloric acid, so it dissolves and CO2 gas is evolved.

Written and checked by Maryam Kashif, M.Phil ChemistryLast updated 1 September 2026

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When a mixture of white solids Z, is treated with an excess of dilute hydrochloric acid, a colorless gas is evolved and some, (but not all) of the mixture dissolve.

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