Chemistry 122 d

Question

What mass of (solid) KCl is needed to prepare 200. mL of 0.65 M solution?

Answer 1

Hi Bailey

the problem states:

what mass of KCl(s) is needed to prepare 200ml of a

0.65M solution?

given: 0.65M KCl

200ml

unknown: grams of KCl needed

steps:

1) find the # of moles in 200ml of a 0.65M solution of the KCl

0.2 L x 0.65mol/L = 0.13mol

2) convert the 0.13 mol to grams needed of the

KCl

molar mass of KCl = 74.54 g

0.13mol x 74.54 g/1 mol = 9.69 g the answer

So to prepare 200 ml of a 0.65M solution of KCl

add 9.69 g of KCl to make 200ml of solution.

3) to check your work:

convert the above answer 9.69 g to mol

and then divide by the amount of volume required, 200ml

9.69 g x 1 mol/74.54 g = 0.123mol/0.2L = 0.65M

i hope this is helpful for you