Calculating Concentrations and Dilutions in Titrations

[TheRedDevil18]

Homework Statement

Kevin must prepare a solution of NaOH with a concentration of 0.2 mol.dm3.
1.1) What mass of solid must he dissolve in 1dm3 of water to make this solution.
1.2) Kevin dissolves too much solid and makes 1dm3 of solution with a concentration of 0.22 mol.dm3. How much water must he add to obtain the correct concentration?

Homework Equations

c = m/MV

The Attempt at a Solution

1.1) I worked the mass to be 8g using the formula.
1.2) Need help on this question. Worked out the additional mass to be 8.8g. How do I find out the amount of water to be added?

 

[Borek]

This is a simple dilution problem. Whatever already is in the solution will be also in the final solution. You have 1 L of a 0.22 M solution - how many moles of NaOH? Starting from C=n/V, can you calculate what should be a final volume if the concentration is to be 0.1 M?