Question

Calculate the grams of solute needed to prepare each of the following.

A.5.00 L of a 2.30 M NaOH solution

Express your answer with the appropriate units.

B.6.00 L of a 0.195 M CaCl2 solution

Express your answer with the appropriate units.

C.290. mL of a 3.20 M NaNO3 solution

Express your answer with the appropriate units.

Answer 1

A)

volume , V = 5 L

use:

number of mol,

n = Molarity * Volume

= 2.3*5

= 11.5 mol

Molar mass of NaOH,

MM = 1*MM(Na) + 1*MM(O) + 1*MM(H)

= 1*22.99 + 1*16.0 + 1*1.008

= 39.998 g/mol

use:

mass of NaOH,

m = number of mol * molar mass

= 11.5 mol * 40 g/mol

= 460 g

Answer: 460 g

B)

volume , V = 6 L

use:

number of mol,

n = Molarity * Volume

= 0.195*6

= 1.17 mol

Molar mass of CaCl2,

MM = 1*MM(Ca) + 2*MM(Cl)

= 1*40.08 + 2*35.45

= 110.98 g/mol

use:

mass of CaCl2,

m = number of mol * molar mass

= 1.17 mol * 1.11*10^2 g/mol

= 1.298*10^2 g

Answer: 130. g

C)

volume , V = 2.9*10^2 mL

= 0.29 L

use:

number of mol,

n = Molarity * Volume

= 3.2*0.29

= 0.928 mol

Molar mass of NaNO3,

MM = 1*MM(Na) + 1*MM(N) + 3*MM(O)

= 1*22.99 + 1*14.01 + 3*16.0

= 85 g/mol

use:

mass of NaNO3,

m = number of mol * molar mass

= 0.928 mol * 85 g/mol

= 78.88 g

Answer: 78.9 g