Dilution and Prep Solutions

Standard Solutioon - a solution with a known concentration

2 Ways to make standard solutions:

1. Dissolve a known mass of solute in a certain volume of solution
2. Dilute a solution of known concentration

Dilution - procedure for preparing less concentrated solutions from concentrated ones

Eg. How would you prepare a 1.0L sample of 0.400 M KMnO${}_4$ solution from a solution of 1.00 M KMnO${}_4$

C = n / V or n = C * V = 0.4 M * 1.0 L = 0.4 mol

$\therefore$ 0.4 mol of KMnO${}_4$ is needed.

Find volume of stock solution:

C = n/V or V = n/C = 0.4 mol / 1.0 M = 0.40 L

NOTICE: C${}_1$ V${}_1$ = n and n = C${}_2$ V${}_2$

$\therefore$ C${}_1$ V${}_1$ = C${}_2$ V${}_2$

Ex. You want to prepare 500 mL of 1.75 M solution of H${}_2$SO${}_4$ from 8.61 M of H${}_2$SO${}_4$ stock solution. What volume of the stock solution must you dilute?

C${}_1$ = 8.61 M V${}_1$ = ?

C${}_2$ = 1.75 M V${}_2$ = 500 mL

C${}_1$ V${}_1$ = C${}_2$ V${}_2$

V${}_1$ = C${}_2$ V${}_2$ / C${}_1$ = $\frac{1.75M\ast 500mL}{8.61M}$ = 102 mL

$\therefore$ Volume of water to be added = 500 mL - 102 mL = 398 mL

Grade 11 Chemistry Homework

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