can someone please tell me what formula's to use for the 2 following chemistry problems.

1. Calculate the solubility of potassium bromide at 23 degrees Celsius. hint. Assume that the solubility increases by an equal amount for each degrees between 20 degrees C and 30 degrees C. at 20 degrees Celsius it is 65.2.
at 30 degrees Celsius it is 70.6.

2. a saturated solution of barium chloride at 30 degrees Celsius contains 150 g of water. How much additional barium chloride can be dissolved by heating this solution to 60 degrees Celsius.
F.Y.I. these are the entire questions I think I could figure it out if I knew what formula to use.

thanking you in advance

3 answers

#1.
Take the solubility at 30 and subtract solubility at 20 and divide by 10. That gives you an average solubility per degree C. You have it at 20, then add 3*solubility/degree and you will have it at 23 c.

#2. Surely you have a solubility curve or a graph that will tell you the solubility at 60 C. There is nothing in the problem that tells you what the solubility is in the saturated solution.
I will make some assumptions for #2.
That the 85.5 g solubility you quote later is 85.5g BaCl2/100 g water @ 60 C. If that's so then you will be able to dissolve 85.5g x (150gH2O/100 gH2O) = approx 128 g BaCl2 that can be dissolved at 60 C. The only piece of information needed from the 30 C solution is the 150 g H2O. Basically, this is the question you are being asked although it is masquerading with that other information. .
If the solubility of BaCl2 at 60 C is 85.5 g BaCl2/100 g H2O, how much BaCl2 can be dissolved in 150 g H2O at 60 C? Stating it that way makes it simpler I think.
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