Question

Please answer the questions below to three significant figures. a) What mass of KCI is required to make 48.0 mL of a 0.140 M KCl solution? g KCI b) How many moles of potassium ions are present in the solution? mol

Answer 1

a)

volume , V = 48 mL

= 4.8*10^-2 L

use:

number of mol,

n = Molarity * Volume

= 0.14*4.8*10^-2

= 6.72*10^-3 mol

Molar mass of KCl,

MM = 1*MM(K) + 1*MM(Cl)

= 1*39.1 + 1*35.45

= 74.55 g/mol

use:

mass of KCl,

m = number of mol * molar mass

= 6.72*10^-3 mol * 74.55 g/mol

= 0.501 g

Answer: 0.501 g

b)

Moles of KCl = 6.72*10^-3 mol

1 mol of KCl has 1 K+ ion

So,

Mol of K+ = mol of KCl

=6.72*10^-3 mol

Answer: 6.72*10^-3 mol