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# calculating the mass that dissolves in a certain amount of water...

Submitted by needhelp on Thu, 08/28/2008 - 18:46

Potassium chloride is widely used in teh manufacture of fertilizers. Its solubiility is 37.0 g/100 g water at 30 celcius. at 70 celcius its solubiiloity is 48.3 g/100 g water.

a. calculate the mass of potassium chloride that dissolves in 44.5 g of water at 30 celcius

b. calculate the mass of water required to dissolve 39.6 g of potassium chloride at 70 celcius

c. if 40.0 g of potassium chloride to 75.0 g of water at 30 celcius will it all dissolve? If the temperature is increased to 70 celcius will it all dissolved? How many grams are undissolved at 30 celcius? at 70? (if any)

what does the solubility ratio mean? what does it represent?

i got the first one right...it was 16.5 g.

i even got the second right..it was 82.0 g

i just didn't get the last one? what are the asking? and how am i supposed to figure it out??

Thank you.

needhelp wrote:

Potassium chloride is widely used in teh manufacture of fertilizers. Its solubiility is 37.0 g/100 g water at 30 celcius. at 70 celcius its solubiiloity is 48.3 g/100 g water.

c. if 40.0 g of potassium chloride to 75.0 g of water at 30 celcius will it all dissolve? If the temperature is increased to 70 celcius will it all dissolved? How many grams are undissolved at 30 celcius? at 70? (if any)

If you calculate the solubility ratio and compare it to the ratio that you are given, then you have the following situations

given ratio > solubility  =  there will be undisolved solute

given ratio < solubility  = all solute will be dissolved

at 30 set up your proportion to see how many grams will dissolve in 75.0 g of water

75.0 g H2O      37.0 g KCl
x    __________ = amount of KCl that will dissolve at 30
100 g H2O