The table shows how the hazard classification of sodium hydroxide solution depends on its concentration.
| Concentration of sodium hydroxide (g dm−3\mathrm{g\,dm^{-3}}gdm−3) | Hazard classification |
|---|---|
| less than 2.0 | low hazard |
| 2.0 up to 20 | irritant |
| 20 or more | corrosive |
A student dissolves 3.0 g of sodium hydroxide in water and makes the solution up to 250 cm3\mathrm{cm^{3}}cm3. This is solution X.
The student then takes 50 cm3\mathrm{cm^{3}}cm3 of solution X and adds water until the total volume is 500 cm3\mathrm{cm^{3}}cm3. This is solution Y.
Which row gives the correct hazard classifications of solutions X and Y?
X: irritant; Y: low hazard
X: irritant; Y: corrosive
X: irritant; Y: irritant
X: low hazard; Y: low hazard
230 exam-style questions on Edexcel GCSE Chemistry 1.1 Formulae, equations and hazards, covering 1.1.1 Formulae, word and balanced equations, 1.1.2 Balanced ionic equations, and 1.1.3 Hazard symbols and risk in practical work. Each one has a worked solution and a mark scheme showing where the marks go.