Question

Complete the following Assignments 1. Calculate the percent (W/V) of a solution made by dissolving 23.4 g sodium chloride in water to make a 250 ml volume of solution. 2. Calculate the number of grams of NaOH needed to make 1500 mL of a 0.2 M solution 3. 5.0 mL of a potassium chloride solution is transferred to a beaker and the water evaporated. The weight of KCl is 0.75 g. a) calculate the molarity b) calculate the percent (w/v) KCI

Answer 1

1)

mass(NaCl)= 23.4 g

V(H2O) = 250.0 mL

use:

(m/v)% = mass of NaCl *100 / volume of H2O in mL

= 23.4*100/250.0

= 9.36 %

Answer: 9.36 %

2)

volume , V = 1.5*10^3 mL

= 1.5 L

use:

number of mol,

n = Molarity * Volume

= 0.2*1.5

= 0.3 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

= 0.3 mol * 40 g/mol

= 12 g

Answer: 12 g

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