ACSBR 5 Salts - Assignment ANS

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ANSWERS ( ) Class: SEC 3 SALTS – ASSIGNMENT ALEX LEE/2010 PAGE 1 OF 4 PURE/COMBINED Multiple-Choice Questions [20 Marks] TOTAL SCORE / 30 Write in your selected answer for the multiple-choice questions in the boxes provided. 1 2 3 4 5 6 7 8 9 10 B B D C C C B A B A 11 12 13 14 15 16 17 18 19 20 C B B D A A B A C B 1. Which of the following ionic compounds is the most soluble in water? A calcium carbonate C silver chloride B magnesium sulfate D zinc hydroxide 2. Which of the following ionic compounds is the least soluble in water? A ammonium carbonate C iron(III) chloride B barium sulfate D lead(II) nitrate 3. Which of the following pairs of salts can be separated by adding water and filtering? A barium chloride, lead(II) nitrate C iron(III) sulfate, zinc nitrate B calcium sulfate, silver chloride D magnesium carbonate, lithium iodide 4. Which two pairs of solutions, when mixed, will produce a precipitate? A barium chloride, potassium nitrate C hydrochloric acid, silver nitrate B copper(II) iodide, sodium nitrate D lead(II) nitrate, zinc nitrate 5. Which two pairs of solutions, when mixed, will not produce a precipitate? A ammonium chloride, silver nitrate C lead(II) nitrate, magnesium nitrate B calcium chloride, sulfuric acid D sodium hydroxide, zinc nitrate 6. Which of the following is not an alkali? A ammonium hydroxide C magnesium hydroxide B calcium hydroxide D sodium hydroxide

ALEX LEE/2010 PAGE 2 OF 4 7. An unknown compound X is insoluble in water and reacts with acids to produce a gas. Which of the following is most likely to be X? A aluminium hydroxide C lithium carbonate B copper(II) carbonate D magnesium metal 8. Aqueous solutions of two salts were mixed. A white precipitate was formed, which was filtered off and transferred to another container. A few drops of dilute hydrochloric acid were added to the solid, and effervescence was observed. What could the two salts be? A ammonium carbonate, barium nitrate C barium chloride, magnesium sulfate B copper(II) chloride, silver nitrate D iron(III) sulfate, sodium hydroxide 9. Which of the following salts should be prepared by titration? A calcium sulfate C magnesium nitrate B lithium chloride D silver nitrate 10. Which of the following salts should be prepared by precipitation? A calcium sulfate C magnesium nitrate B lithium chloride D silver nitrate 11. Jeremy wishes to prepare a sample of potassium chloride. Which of the following solutions would not be suitable as a starting reagent? A potassium carbonate C potassium nitrate B potassium hydroxide D hydrochloric acid 12. Which pair of substances can be used in the preparation of zinc sulfate? A aqueous zinc nitrate, aqueous sodium sulfate B zinc metal, dilute sulfuric acid C solid zinc carbonate, aqueous zinc chloride D solid zinc oxide, aqueous ammonium sulfate 13. Which pair of substances can be used in the preparation of iron(II) hydroxide? A aqueous iron(II) chloride, aqueous potassium iodide B aqueous iron(II) nitrate, aqueous sodium hydroxide C dilute iron(II) oxide, dilute hydrochloric acid D solid iron(II) nitrate, potassium hydroxide 14. A student had to prepare a sample of magnesium sulfate. He chose a solid to add to dilute sulfuric acid. The preparation failed. Which solid had he chosen? A magnesium carbonate C magnesium metal B magnesium hydroxide D magnesium nitrate

ALEX LEE/2010 PAGE 3 OF 4 15. Which of the following substances should be added to dilute sulfuric acid to prepare lead(II) sulfate? A aqueous lead(II) nitrate C powdered lead(II) carbonate B lead metal D powdered lead(II) chloride 16. Michelle wishes to prepare a sample of zinc chloride. She executes the following steps: Step 1: Wash and dry and crystals formed. Step 2: Add excess zinc carbonate to the solution. Step 3: Heat the filtrate over an evaporating dish. Step 4: Place some dilute hydrochloric acid into a beaker. Step 5: Filter out the excess solid. In which order should the above steps be carried out? A 4, 2, 5, 3, 1 C 4, 3, 2, 1, 5 B 2, 5, 4, 1, 3 D 4, 2, 3, 5, 1 17. Which one of the following hydroxides does not give a good yield of a salt with dilute hydrochloric acid? A iron(III) hydroxide C magnesium hydroxide B lead(II) hydroxide D zinc hydroxide 18. How can barium sulfate be best be prepared from barium carbonate? A Add dilute nitric acid, followed by potassium sulfate and filter. B Add dilute sulfuric acid and filter. C Add dilute sulfuric acid, followed by potassium sulfate and filter. D Add excess water, followed by dilute nitric acid. 19. Which of the following describes a step in the preparation of aqueous barium chloride? A Add an indicator. C Filter the mixture. B Add barium sulfate. D Heat in evaporating dish. 20. In the preparation of copper(II) sulfate, why is copper metal a poor choice of reactant to add to the dilute sulfuric acid? A A soluble reactant should be used instead. B Copper is a very unreactive metal. C Copper is very expensive. D Metals do not react with acids.

ALEX LEE/2010 PAGE 4 OF 4 Structured Questions [10 Marks] 21. (a) Write chemical equations, including state symbols, for the following precipitation reactions: (i) aqueous barium chloride + dilute sulfuric acid [1] BaCl2 (aq) + H2SO4 (aq) ⎯→ BaSO4 (s) + 2 HCl (aq) (ii) aqueous potassium hydroxide + aqueous iron(III) sulfate [1] 6 KOH (aq) + Fe2(SO4)3 (aq) ⎯→ 2 Fe(OH)3 (s) + 3 K2SO4 (aq) (b) Lead(II) chloride is an insoluble salt, and can be prepared by mixing solutions of lead(II) nitrate and potassium chloride. (i) State the chemical equation, including state symbols, for this reaction. [1] Pb(NO3)2 (aq) + 2 KCl (aq) ⎯→ 2 KNO3 (aq) + PbCl2 (s) (ii) Outline the steps, after mixing, to obtain a dry sample of the salt. [1] Filter the solution, wash the residue with distilled water, and allow the residue to dry between sheets of filter paper. 22. Sodium phosphate, Na3PO4, is a soluble salt, used as a water softener in washing powders. It is prepared by reacting dilute phosphoric acid, H3PO4, with an alkali. (a) Name the alkali that should be used. [1] Aqueous sodium hydroxide (b) Give the formulae of the ions present in sodium phosphate. [1] Na+, PO43- (c) Construct a balanced chemical equation, including state symbols, for the reaction between dilute phosphoric acid and the alkali. [1] H3PO4 (aq) + 3 NaOH (aq) ⎯→ Na3PO4 (aq) + 3 H2O (l) (d) Given solutions of phosphoric acid and alkali, a suitable indicator and standard laboratory apparatus, explain how you would prepare an aqueous sample of sodium phosphate. [3] Using a pipette, extract a fixed volume of dilute H3PO4 into a flask. Add a few drops of phenolphthalein. (1) Using a burette, add aqueous NaOH drop by drop until neutralisation. (2) Note volume of NaOH used. Repeat without indicator. (3) END