Hkcee (ch

HKCEE - Ch.19 Neutralization and salts

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97II(13) Which of the following statements concerning the reaction of aqueous ammonia with hydrochloric is correct? A. The reaction is exothermic. B. A white precipitate is formed. C. Ammonium chloride and chlorine are produced. D. The product ammonium chloride is a covalent compound. A 98II(13) In an experiment, 10cm3 of 1M hydroxide acid is added slowly into 10cm3 of 1M sodium hydroxide solution. Which of the following statements concerning this experiment is correct? A. The temperature of the mixture increases. B. The pH of the mixture increases. C. The mixture does not conduct electricity at the end of the experiment. D. The concentration of sodium ions in the mixture remains unchanged. A 96II(4)

Consider the following chemical equation: 2HNO3(aq) + CaCO3(x)  Ca(NO3)2(y) + H2O(z) + CO2(g) Which of the following combinations is correct? x y z A. aq aq l B. aq aq aq C. s aq l D. s s aq

C 00II(18) Some potassium carbonate solution is added to a sample of tap water. The mixture then appears cloudy. Which of the following ions is probably present in the sample? A. NH4+ B. Mg2+ C. BrD. SO42B

HKCEE - Ch.19 Neutralization and salts

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97II(27) Consider the following chemical equation: O2(g) + 4Fe(OH)2(x)  2Fe2O3(y) + 4H2O(z) Which of the following combinations is correct? x y z A. s s l B. s aq aq C. aq s aq D. aq aq l A 97I(a) Answers i. H2SO4 + CuCO3  CuSO4 + CO2+ H2O (1) ii. To ensure that all the sulphuric acid has been used up/ malachite in excess (1) iii. (Award 0m for this part if the set-up is not workable.) (1m for showing the filter funnel and filter paper. 1m for showing the collection of the filtrate. 1m for labeling filter paper and residue) Total: 3m 00I6(aii) The flow diagram below shows the stages involved in the extraction of zinc from zinc blende, ZnS. Stage 1: roasting Stage II Stage III: electrolysis Zinc blende -------------> zinc oxide ------> zinc sulphate solution ------>zinc Suggest how zinc oxide can be converted to zinc sulphate solution in Stage II. Use dilute sulphuric acid to dissolve zinc oxide. (1) 02I(7a)

Calcite is a mineral which contains mainly calcium carbonate. An experiment, consisting of the following the following five stages, was conducted to percentage by mass of calcium carbonate in a sample of calcite. Stage 2: Filter the mixture obtained in Stage 1 to remove any undissolved solid. Stage 3: Add excess sodium sulphate to the filtrate to precipitate out calcium sulphate. Stage 4: Collect the calcium sulphate precipitate and wash it with distilled Water

HKCEE - Ch.19 Neutralization and salts

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(ii) Draw a labeled diagram of the set-up used in the filtration process in Stage2. (2) (iii) Write the ionic equation for the reaction in Stage 3. (1) (iv) Explain why it is necessary to wash the precipitate with distilled water in Stage 4. (1) (ii) 1m for diagram, 1m for labeling the funnel and filter paper (iii) SO42- + Ca2+  CaSO4 (1) (iv) to remove any soluble impurities (or appropriate e.g. Na2SO4, HNO3, NaNO3)(1) 96II(6)

Which of the following substances is used by farmers to increase the pH of soil? A. ammonium nitrate B. Calcium hydroxide C. Citric acid D. Potassium hydroxide (expensive)

B 98II(31) What is the purpose of adding quicklime (calcium oxide) to soil? A. to neutralize the acidity of the soil B. to act as a fertilizer for the soil C. to kill micro-organisms in the soil D. to increase the amount of calcium ions in the soil A 00II(49) 1: Adding lime to acidic soil can increase crop yield. 2: Lime can neutralize the acid to the soil. A 02I(1cii) Both ammonium dihydrogenphosphate and ammonium sulphate are nitrogenous fertilizer. The use of ammonium sulphate as a fertilizer adds acidity to the soil. If the soil is too acidic, it is not suitable for plant growth. Suggest ONE substance that is commonly used by farmers to reduce soil acidity. Explain your answer. Calcium hydroxide/ calcium oxide/ calcium carbonate (accept formula and common name, Not accept NaOH) 1 Explanation: Calcium hydroxide/ calcium oxide/ calcium carbonate reacts with H+ in soil

HKCEE - Ch.19 Neutralization and salts

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(neutralizes acid in soil) 1 Or Ca(OH)2. CaO/ CaCO3 is not very soluble in water. It will not make the soil too alkaline. (1) Alternative answer: Ammonia solution/ NH3(aq) (1) Explanation: Ammonia reacts with H+ in soil (neutralizes acid in soil.) (1) Ammonia is a weak alkali. It will not increase the soil pH to a great extent. (1) 95II(35) Which of the following substances, when mixed with lemon juice, would give off gas bubbles? 1. iron nails 2. milk of magnesia 3. polyethene wrap A. 1 only B. 2 only C. 1 and 3 only D. 2 and 3 only A 03II(45) 1: Sodium hydroxide is an active ingredient in anti-acid tablets. 2: Sodium hydroxide is a strong alkali. C 00I(6bi2) In Hong Kong, the supply of fresh water mainly comes from Dong Jiang. After some preliminary treatment of the river water in the water treatment plants, chlorine and calcium hydroxide are successively added. Why are calcium hydroxide added to the river water? (1) To react with acidic substances in fresh water/ to regulate the pH/ to precipitate ions of heavy metals/ to prevent corrosion of water pipes 98. 6. a.

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(1) NaOH + HNO3  NaNO3 + H2O (1) (2) (1 mark for a diagram showing the set-up for the titration (1) experiment; (2 marks for labeling the apparatus and reagents.) (2) (3) form pink/ purple/ red to colourless (1) (4) Add dilute nitric acid to 1M sodium hydroxide solution in the (1)

HKCEE - Ch.19 Neutralization and salts same volume ratio as that in the titration result, without adding the indicator or repeat the titration procedure without adding the indicator. (1)

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