7.3. Preparation of salts
A subsection of Chemistry, 0620, through 7. Acids, bases and salts
Listing 10 of 150 questions
Three ways of making salts are ● titration using a soluble base or carbonate ● neutralisation using an insoluble base or carbonate ● precipitation. Complete the following table of salt preparations. method reagent 1 reagent 2 salt titration sodium nitrate neutralisation nitric acid copper(nitrate precipitation silver(chloride neutralisation sulfuric acid zinc(carbonate Write an ionic equation with state symbols for the preparation of silver(chloride. Complete the following equation. ZnCO3 + H2SO4 → + +
0620_s12_qp_31
THEORY
2012
Paper 3, Variant 1
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Propanol is a solvent. Sugar is soluble in propanol. Salt (sodium chloride) is insoluble in propanol. A student wants to separate a mixture of solid salt and solid sugar. Describe how she could separate the salt from the sugar. You may draw a labelled diagram to help you answer this question. Describe how the student could obtain solid sodium chloride from a solution of sodium chloride in water. The diagram shows the structure of sodium chloride. Na+ Cl – Na+ Cl – Na+ Na+ Cl – Cl – Na+ Cl – Na+ Cl – Na+ Na+ Cl – Cl – Deduce the simplest formula for sodium chloride. What type of bonding is present in sodium chloride? Put a ring around the correct answer. covalent ionic metallic weak The diagram shows the apparatus used to electrolyse a concentrated aqueous solution of sodium chloride. + – A C D B Which letter on the diagram, A, B, C or D, represents the electrolyte? Name the product formed at the positive electrode, the negative electrode.
0620_s13_qp_21
THEORY
2013
Paper 2, Variant 1
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The soluble salt hydrated lithium sulfate is made by titration from the soluble base lithium hydroxide. burette filled with sulfuric acid aqueous lithium hydroxide and a few drops of a pH indicator conical flask The sulfuric acid is added slowly from the burette until the indicator just changes colour. The volume of sulfuric acid needed to just neutralise the lithium hydroxide is noted. Describe how you would continue the experiment to obtain pure dry crystals of hydrated lithium sulfate. Using 25.0 cm3 of aqueous lithium hydroxide, concentration 2.48 mol / dm3, 2.20 g of hydrated lithium sulfate was obtained. Calculate the percentage yield, giving your answer to one decimal place. 2LiOH + H2SO4 → Li2SO4 + 2H2O Li2SO4 + H2O → Li2SO4.H2O Number of moles of LiOH used = Number of moles of Li2SO4.H2O which could be formed = Mass of one mole of Li2SO4.H2O = 128 g Maximum yield of Li2SO4.H2O = g Percentage yield = % An experiment was carried out to show that the formula of the hydrated salt is Li2SO4.H2O. A sample of the hydrated salt was weighed and its mass recorded. It was then heated and the anhydrous salt was weighed. This procedure was repeated until two consecutive masses were the same. This procedure is called ‘heating to constant mass’. What is the reason for heating to constant mass? The mass of the hydrated salt is m1 and the mass of the anhydrous salt is m2. Explain how you could show that the hydrated salt has one mole of water of crystallisation per mole of the anhydrous salt.
0620_s14_qp_32
THEORY
2014
Paper 3, Variant 2
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Three common methods of preparing salts are shown below. method A adding an excess of an insoluble base or carbonate or metal to a dilute acid and removing excess by fi ltration method B using a burette and indicator method C mixing two solutions to obtain the salt by precipitation For each of the following salt preparations, choose a method, A, B or C. Name any additional reagent which is needed and complete the equation. the soluble salt, nickel chloride, from the insoluble compound nickel carbonate method reagent word equation the insoluble salt, lead(bromide, from aqueous lead(nitrate method reagent ionic equation + → PbBr2 the soluble salt, lithium sulfate, from the soluble base lithium hydroxide method reagent equation
0620_s15_qp_32
THEORY
2015
Paper 3, Variant 2
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Questions Discovered
150