Question

Solution Concentration, Dilution, and Properties of Solutions (Ch.9) 1. How many grams of KCl are in 20.0 mL of a 10% (m/v) KCl solution? 20ml 10 a a.aramo 100 YOO = a Anwser ag of KCI 2. How much water would need to be added to the 20.0mL of 10% (m/v) KCl to make a solution that is 5.0% (m/v) KCI? olom a x 100 = 5 10o = 5 ao tu u=20ml 200 - 5(20+0) Anwser = 20ml nnnnnn icotonic in colle? What

Answer 1

1)

Given:

(m/v)% = 10 %

volume of solution = 20.0 mL

Use:

(m/v)% = mass of KCl * 100 / volume of solution

10 = mass of KCl * 100 / 20.0 mL

mass of KCl = 2.00 g

Answer: 2.00 g

2)

use dilution formula

M1*V1 = M2*V2

1---> is for stock solution

2---> is for diluted solution

Given:

M1 = 10 %

M2 = 5 %

V1 = 20 mL

use:

M1*V1 = M2*V2

V2 = (M1 * V1) / M2

V2 = (10*20)/5

V2 = 40 mL

SO,

Volume of water added = V2 - V1

= 40 mL - 20 mL

=20 mL

Answer: 20.0 mL