A technician makes sodium hydroxide solutions for a class.
The technician dissolves 12.0 g of sodium hydroxide, NaOH, in water and makes the solution up to exactly 500 cm3\mathrm{cm^{3}}cm3 in a volumetric flask.
Calculate the concentration of this solution in g/dm3\mathrm{g/dm^{3}}g/dm3.
Concentration = ...... g/dm3\mathrm{g/dm^{3}}g/dm3
Calculate the concentration of this solution in mol/dm3\mathrm{mol/dm^{3}}mol/dm3.
Relative atomic mass (Ar): H = 1.0 Na = 23.0 O = 16.0
Concentration = ...... mol/dm3\mathrm{mol/dm^{3}}mol/dm3
The technician also needs 250 cm3\mathrm{cm^{3}}cm3 of sodium hydroxide solution with a concentration of 0.200 mol/dm3\mathrm{mol/dm^{3}}mol/dm3.
Calculate the mass of sodium hydroxide the technician needs.
Mass = ...... g
A student says:
"If I dissolve the same mass of sodium hydroxide in twice the volume of solution, the concentration will double."
Explain why the student is wrong.
57 exam-style questions on OCR GCSE Chemistry 5.1 Monitoring chemical reactions, covering 5.1.1 The technique of titration, 5.1.2 Theoretical mass, percentage yield and atom economy, 5.1.3 Concentration of a solution in mol/dm3, 5.1.4 Concentration calculations and titration results, 5.1.5 Molar gas volume and volumes of gases in reactions, and 5.1.6 Choosing a reaction pathway. Each one has a worked solution and a mark scheme showing where the marks go.