Question

Mellissa dissolves 26. grams of NaF with water to make a 199. mL solution. What is the molarity of the solution? There are 1,000 mL in 1 L.

Tamara has 107 g of a NaCl solution that has concentration of 4.5 % NaCl (m/m). How many grams of NaCl are dissolved in that solution?

Answer 1

1)

Molar mass of NaF = 1*MM(Na) + 1*MM(F)

= 1*22.99 + 1*19.0

= 41.99 g/mol

mass of NaF = 26 g

we have below equation to be used:

number of mol of NaF,

n = mass of NaF/molar mass of NaF

=(26.0 g)/(41.99 g/mol)

= 0.6192 mol

volume , V = 199 mL

= 0.199 L

we have below equation to be used:

Molarity,

M = number of mol / volume in L

= 0.6192/0.199

= 3.1 M

Answer: 3.1 M

2)

mass % = mass of NaCl * 100 / mass of solution

4.5 = mass * 100 / 107

mass = 4.8 g

Answer: 4.8 g