solubility of ionic salts

[epsilonprodigy]

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There is a GS question that says that CaSO4 is less soluble than Ca(OH)2.

The reasoning is that, according to Ksp,

CaSO4= (Ca2+)(SO4-)= (x)(x)= x^2

Ca(OH)2= (Ca2+)(2 OH-)^2= (x)(2x)^2=4x^3

4x^3 > x^2

BUT...... CaSO4 gives rise to FEWER IONS...so, wouldn't it be more soluble??

 

[Aiu]

Fewer ions = less solid dissolved = less soluble.

 

[Pons Asinorum]

There is a GS question that says that CaSO4 is less soluble than Ca(OH)2.

The reasoning is that, according to Ksp,

CaSO4= (Ca2+)(SO4-)= (x)(x)= x^2

Ca(OH)2= (Ca2+)(2 OH-)^2= (x)(2x)^2=4x^3

4x^3 > x^2

BUT...... CaSO4 gives rise to FEWER IONS...so, wouldn't it be more soluble??

You need the actual Ksp values, solve for the values of x for the two compounds and compare them. You can't just compare them algebraically, unless their Ksp's are equal, which I doubt.

 

[chemtopper]

Ksp value indicates the degree to which a compound dissociates in water.You need to compare the ksp of these two compounds to compare the suitabilities.