Question

How many grams of potassium chloride (KCl) can be dissolved in 68.0g of water at 40°C? Please help.

Answer 1

Answer:

The problem provides you with the solubility of potassium chloride,

KCl

, in water at

20

∘

C

, which is said to be equal to

34 g / 100 g H

2

O

.

This means that at

20

∘

C

, a saturated solution of potassium chloride will contain

34 g

of dissolved salt for every

100 g

of water.

As you know, a saturated solution is a solution that holds the maximum amount of dissolved salt. Adding more solid to a saturated solution will cause the solid to remain undissolved.

In your case, you can create a saturated solution of potassium chloride by dissolving

34 g

of salt in

100 g

of water at

20

∘

C

.

Now, your goal here is to figure out how much potassium chloride can be dissolved in

300 g

of water at this temperature. To do that, use the given solubility as a conversion factor to take you from grams of salt to grams of water

300

g H

2

O

⋅

34 g KCl

100

g H

2

O

=

102 g KCl

You should round this off to one sig fig, since that is how many sig figs you have for the mass of water

∣

∣

∣

∣

¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯

a

a

mass of KCl

=

100 g

a

a

∣

∣

−−−−−−−−−−−−−−−−−−−−−−−

Explanation: