Wall paint is a formulation.
The table shows the components of one paint.
| Component | Percentage by mass (%) | Job in the paint |
|---|---|---|
| titanium dioxide | 22 | pigment: gives the white colour |
| acrylic polymer | 35 | binder: sticks the pigment to the wall and forms a hard film |
| water | 38 | solvent: makes the paint runny so it spreads |
| additives | ? | stop mould growing and help the paint flow |
Explain why the paint is described as a formulation.
Calculate the percentage by mass of additives in the paint.
A tin contains 2.5 kg of paint.
Calculate the mass of titanium dioxide in the tin. Give your answer in grams.
The manufacturer makes a cheaper paint. It contains 50% water and only 23% acrylic polymer.
Suggest one disadvantage of the cheaper paint. Explain your answer using the table.
The paint tin is labelled "pure brilliant white".
Explain why a chemist would not describe the paint as pure.
51 exam-style questions on OCR GCSE Chemistry 2.1 Purity and separating mixtures, covering 2.1.1 Pure substances and melting point data, 2.1.2 Relative formula mass and empirical formula, 2.1.3 Formulations as useful mixtures, 2.1.4 Techniques for separating mixtures, and 2.1.5 Chromatography and Rf values. Each one has a worked solution and a mark scheme showing where the marks go.