Question

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

Part A

2.0 L of a 6.0 M NaOH solution

Express your answer using two significant figures.

Part B

7.0 L of a 0.20 M CaCl2 solution

Express your answer using two significant figures.

Part C

165 mL of a 2.50 M NaNO3 solution

Express your answer using three significant figures.

Answer 1

A)

volume , V = 2 L

use:

number of mol,

n = Molarity * Volume

= 6*2

= 12 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

= 12 mol * 40 g/mol

= 4.8*10^2 g

Answer: 4.8*10^2 g

B)

volume , V = 7 L

use:

number of mol,

n = Molarity * Volume

= 0.2*7

= 1.4 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

= 1.4 mol * 1.11*10^2 g/mol

= 1.554*10^2 g

Answer: 1.6*10^2 g

C)

volume , V = 1.65*10^2 mL

= 0.165 L

use:

number of mol,

n = Molarity * Volume

= 2.5*0.165

= 0.4125 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

= 0.4125 mol * 85 g/mol

= 35.06 g

Answer: 35.1 g