189k views
2 votes
Which calcium compound is not appreciably more soluble in 0.1 m hydrochloric acid than it is in pure water? (a) limestone, caco3 (b) slaked lime, ca(oh)2 (c) gypsum, caso4 • 2 h2o (d) hydroxyapatite, ca5(oh)(po4)3?

1 Answer

3 votes
The answer is "c", "Gypsum, CaSO₄ • 2 H₂O".
Because in option A,B and D there is a component which acts as a base and reacts with the acid like CO₃²⁻ in limestone, CaCO₃, OH⁻ in slaked lime, Ca(OH)₂ and OH⁻ in hydroxyapatite, Ca₅(OH)(PO₄)₃.
However in Gypsum, CaSO₄ • 2 H₂O, SO₄²⁻ are weak bases as they are the conjugate bases of strong acid HSO .
Thus option C shows minimum tendency of reaction with HCl and hence minimum solubility.

User Waqas Ghouri
by
8.3k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.