A, b and c have the following solubilities in 100 ml of water at 25°c, respectively: 15g, 35 g and 65 g. if 75 g of each are added to 200 ml water, which will completely dissolve? how much of each will remain undissolved?

Only C can dissolve in water because its solubility is greater than 0.375 g/mL

C dissolves completely

22.5 g of A remain undissolved in 100 mL of water

2.5 g of B remain undissolved  in 100 mL of water

Explanation:

Solubility : The amount of salt that can be dissolved in a given volume of solvent at a particular temperature .

For each salt the solubility of 75 g in  200 mL water is

0.375 g/mL

This mean 1 ml of water has 0.375 g of A , B and C

100 mL of water contain = 37.5 g of each salt A , B,C

In the question , the solubility of A , B and C in 100 are given as :

A =  15 g : It means maximum 15 g of A can dissolve in 100 mL

= 0.15 g/mL

B = 35 g  : It means maximum 35 g of B can dissolve in 100 mL

= 0.35 g/mL

C = 65 g : It means maximum 65 g of A can dissolve in 100 mL

= 0.65 g/mL

Since ,Solubility of A and B is less than 0.375 g/mL

So A and B  can't dissolve in water at 25°C

A is excess by 37.5 - 15 = 22.5 g

B is in excess by 37.5 - 35 = 2.5 g

Hence 22.5 g of A remain undissolved

Hence  2.5 g of B remain undissolved

Only C can dissolve in water because its solubility is greater than 0.375 g/mL

"standard molar enthalpy:

h2o ( liquid water ) : - 285.8 kj/mole

h2o ( water vapor ) : - 241.8 kj / mole.

δhrxn = - 241. 8 - ( - 285.8 )= -241.8 + 285.8 = 44.0

answer: 44.0 kj"