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Chemistry Forums for Students => Inorganic Chemistry Forum => Topic started by: Moronic_Acid on January 19, 2011, 11:40:31 AM

Title: Exam style question on solubility
Post by: Moronic_Acid on January 19, 2011, 11:40:31 AM

Exam question on a past paper got the exam tomorrow :( i know its probably quite easy but i don't know where to start any help would be appreciated.

two solutions, each at the same temperature (298 K).
SOLUTION 1: calcium hydrogen phosphate (CaHPO4) dissolved in water;
SOLUTION 2: calcium hydrogen phosphate (CaHPO4) dissolved in a solution
already containing 0.05 M of hydrogen phosphate ions (HPO4)2–

By what factor is the concentration of calcium ions higher in Solution 1 than Solution 2,
given that the solubility product Ksp of calcium hydrogen phosphate is 2.0 x 10(–30) at 298 K?

Title: Re: Exam style question on solubility
Post by: sjb on January 19, 2011, 12:53:58 PM

Quote from: Moronic_Acid on January 19, 2011, 11:40:31 AM

Exam question on a past paper got the exam tomorrow :( i know its probably quite easy but i don't know where to start any help would be appreciated.

two solutions, each at the same temperature (298 K).
SOLUTION 1: calcium hydrogen phosphate (CaHPO4) dissolved in water;
SOLUTION 2: calcium hydrogen phosphate (CaHPO4) dissolved in a solution
already containing 0.05 M of hydrogen phosphate ions (HPO4)2–

By what factor is the concentration of calcium ions higher in Solution 1 than Solution 2,
given that the solubility product Ksp of calcium hydrogen phosphate is 2.0 x 10(–30) at 298 K?

Well, for starters, what is the solubility of pure calcium hydrogen phosphate in distilled water?