temperature of dependence of salt solubility?

Question

I put 3.5g of potassium chloride (KCl) in one test tube with 10 mL of water. I put it on a constant temperature bath at 80 degrees Celsius. Some of the potassium chlorate dissolved and some of it remained solid. Once all of it had dissolved, I took it off the bath, and let it cool down. I recorded the temperature at which the potassium chloride just began to crystallize. (It was 23.95 degrees C) I repeated this with three other beakers- one with 4g of potassium chloride, one with 4.5g and one with 5g.

My two questions are-
Why is it important to not allow the test solutions to boil?

and

Why is it better to determine the initial crystallization temperature during cool down rather than the temperature at which all of the salt dissolves?

Answer 1

1) you don't want to change the volume of the solution, boiling would alter this far more than evaporation from an 80 degree solution.

2) It is harder to see the point at which all the salt has dissolved and it dissolved through agitation as well as increase in temperature, i.e. as you would warm it up it doesn't all dissolve for the saturation point of that temperature immediately. It is far easier to note the crystallisation point when cooling.

Answer 2

when water boils you loose volume due to steam and the water does not get any hotter.

Both temperatures could be significant, depending upon what you want to find out, however, the salt dissolves at lower temperatures, just more slowly. But, the crystalization temp. is an accurate number and precise.

Answer 3

a million) Temperature of water- many times the hotter the better positive 2) floor section publicity- so in case you combine it better it really is going to dissolve swifter, and in case you fall down up a solvent it really is going to dissolve swifter. this gained't impact the saturation of the answer, yet will impact the speed 3) the steadiness, and the chemical composition of the sovent 4) The polarity

Answer 4

from different temp points you can generate a curve and calc temp dependence from there