A student prepares hydrated copper sulfate crystals from copper oxide, an insoluble base.
The student warms some dilute acid in a water bath and adds copper oxide until some black solid remains after stirring. The student then filters the mixture, heats the filtrate to evaporate some of the water and leaves it to crystallise.
Name the acid the student uses.
Explain why the student adds copper oxide until some remains unreacted.
Give one reason for warming the acid in a water bath rather than heating it directly with a Bunsen burner.
79.5 g of copper oxide produces 249.5 g of hydrated copper sulfate crystals. Calculate the maximum mass of crystals that can be made from 2.00 g of copper oxide. Give your answer to three significant figures.
The student obtains 4.71 g of crystals. Calculate the percentage yield. Use the equation: percentage yield=actual yieldtheoretical yield×100\displaystyle \text{percentage yield} = \frac{\text{actual yield}}{\text{theoretical yield}} \times 100percentage yield=theoretical yieldactual yield×100
Explain why the student should not heat the solution until all the water has evaporated.
44 exam-style questions on Edexcel GCSE Chemistry 4.1 Acids, covering 4.1.1 Acids, alkalis and the pH scale, 4.1.2 Hydrogen ion concentration and pH, 4.1.3 Dilute and concentrated, weak and strong acids, 4.1.4 Bases, alkalis and the reactions of acids, 4.1.5 Chemical tests for hydrogen and carbon dioxide, 4.1.6 Neutralisation as a reaction of acids with bases, 4.1.7 Preparing soluble salts, and 4.1.8 Solubility rules and preparing insoluble salts. Each one has a worked solution and a mark scheme showing where the marks go.