7.3. Preparation of salts
A subsection of Chemistry, 0620, through 7. Acids, bases and salts
Listing 10 of 150 questions
For Examiner's Use There are three methods of preparing salts. Method A – use a burette and an indicator. Method B – mix two solutions and obtain the salt by precipitation. Method C – add an excess of base or a metal to a dilute acid and remove the excess by filtration. For each of the following salt preparations, choose one of the methods A, B or C, name any additional reagent needed and then write or complete the equation. the soluble salt, zinc sulphate, from the insoluble base, zinc oxide method reagent word equation the soluble salt, potassium chloride, from the soluble base, potassium hydroxide method reagent equation + → KCl + H2O the insoluble salt, lead(iodide, from the soluble salt, lead(nitrate method reagent equation Pb2+ + →
0620_s07_qp_3
THEORY
2007
Paper 3, Variant 0
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For Examiner's Use Pure dry crystals of magnesium sulphate can be made by reacting excess magnesium powder with dilute sulphuric acid. During the reaction, bubbles of a colourless gas are given off. State the name of this gas. Why is excess magnesium used? How is the excess magnesium removed from the reaction mixture? Describe how you can obtain pure dry crystals of magnesium sulphate from a solution of magnesium sulphate. Describe one other reaction that makes magnesium sulphate. Write a word equation for the reaction you suggested in part . Magnesium sulphate can be used as a medicine. Explain why the chemicals used in medicines need to be as pure as possible. For Examiner's Use A student repeats the experiment using excess sulphuric acid. She obtains 24 g of magnesium sulphate from 4.8 g of magnesium. How much magnesium sulphate can the student obtain from 1.2 g of magnesium? A sample of 20 g of impure magnesium sulphate contains 19.5 g of magnesium sulphate. Calculate the percentage purity of the magnesium sulphate.
0620_s08_qp_2
THEORY
2008
Paper 2, Variant 0
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Questions Discovered
150