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Ammonia worksheet

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This chemistry worksheet provides solutions to multiple choice and free response questions about ammonia and nitrogen-containing compounds. Key points addressed include: 1) Chemical equations for the production of ammonia from nitrogen and hydrogen gases and the reaction of ammonia with carbon dioxide. 2) Percentage composition of nitrogen in ammonium nitrate and its role as a fertilizer. 3) Reactions of ammonium nitrate with calcium hydroxide and uses of calcium nitride. 4) Processes for obtaining nitrogen from air and producing ammonia via the Haber process. 5) Tests to identify ammonia and nitrogen gases and calculations involving moles and volumes.

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Chemistry Worksheet Ammonia Suggested Answer Paper 1 Multiple Choice Questions 1. D 2. C 3. B 4. A 5. C 6. B 7. D 8. A 9. C 10. C 11. D 12. A 13. A 14. C 15. B Paper 2 Section A 1(a) 2NH3(g) + CO2(g) CON2H4(s) + H2O(l) (b) (i) volume of NH3 / volume of CO2 = 2/1 volume of NH3 = 2 144 dm3 = 288 dm3 (ii) no. of moles of CON2H4 = no. of moles of CO2 = 144/24 = 6 mol mass of CON2H4 = 6 [12 + 16 + 2(14) + 4(1)] = 360 g (c) Ammonium nitrate, NH4NO3 / Ammonium sulfate, (NH4)2SO4 2 (a) Percentage by mass of nitrogen in ammonium nitrate = 2(14) / [2(14) + 4(1) + 3(16)] 100% = 35.0 % (b) Ammonium nitrate increases the nitrogen content of the soil. Plants need nitrogen to build proteins for plant growth, and thus lead to increased yield of crops. (c) (i) Calcium hydroxide is added to neutralise the excess acids in the soil so that crops can grow better. (ii) Calcium hydroxide is an alkali and will react with the ammonium ions in ammonium nitrate, converting it into ammonia gas. The ammonia gas will escape from the soil into the air. Thus, the plants are unable to absorb the nitrogen from the fertiliser. 3 (a) Ca3N2(s) + 6H2O(l) 3Ca(OH)2(s) + 2NH3(g)
(b) Calcium reacts with nitrogen according to the equation: 3Ca(s) + N2(g) Ca3N2(s) No.of moles of Ca3N2 produced = 1/3 2 No. of moles of NH3 produced = 1/3 2 2 Thus, mass of NH3 produced = 1/3 4 [14 + 3(1)] = 22.7 g Section B 1(a) (i) N2(g) + 3H2(g) 2NH3(g) (ii) Nitrogen is obtained by the fractional distillation of liquid air. Air is first cooled and compressed into liquid. The liquid air is then heated to separate its components by fractional distillation. The gases in air are distilled in order of their boiling points, and nitrogen is collected at its boiling point of -196属C. (iii) Iron is used as the catalyst. The other conditions used in the Haber process are: (I) a high pressure of 200 atm; and (II) a moderately high temperature of 450属C.. (b) Mass of nitrogen in 1000 kg of the compound = 2(14) / [2(14) + 9(1) + 31 + 4(16)] 1000 kg = 212.12 kg (c) Test 1: Place a piece of damp red litmus paper into each jar. If the gas in the jar turns the damp red litmus paper blue, that jar contains ammonia gas. Test 2: Place a lighted splint into the mouth of each gas jar. If the gas in the jar extinguished the lighted splint with a pop sound, that jar contains hydrogen gas. The gas jar with a gas that has no effect on the damp red litmus paper and extinguished the lighted splint, contains nitrogen gas. 2 (a) (i) Ammonia gas. (ii) (NH4)2SO4(s) + CaO(s) CaSO4(s) + H2O(l) + 2NH3(g)
(iii) no. of moles of (NH4)2SO4 = 3.3 / [2(14) + 8(1) + 32 + 4(16)] = 0.025 mol no. of moles of NH3 = 2 0.025 = 0.05 mol volume of NH3 = 0.05 24 dm3 = 1.2 dm3 (b) Blue precipitate formed. The blue precipitate dissolved in excess of ammonia to form a dark blue solution. Ammonia gas dissolved in water to form an alkaline solution (aqueous ammonia): NH3(g) + H2O(l) NH4+(aq) + OH-(aq) Aqueous ammonia contains hydroxide ions. The hydroxide ions will then react with the copper(II) ions (Cu2+), from copper(II) nitrate solution to form a blue precipitate of copper(II) hydroxide. Cu2+(aq) + 2OH-(aq) Cu(OH)2(s) The copper(II) hydroxide reacts with excess ammonia to form a soluble complex ion. 3 (a) (i) Increasing the pressure increases the percentage of nitrogen and hydrogen that reacts to become ammonia. (ii) Increasing the temperature decreases the percentage of nitrogen and hydrogen that reacts to become ammonia. (b) (i) About 22 % (ii) Advantage: At 400属C, the percentage of nitrogen and hydrogen that reacts to become ammonia is greater than at 500属C. So greater amount of ammonia will be produced. Disadvantage: At 400属C, the reaction proceeds slower than at 500属C. (c) (i) In the manufacture of margarine from vegetable oil, the catalyst use is nickel metal. (ii) Catalyst is not used up during the chemical reaction in which they catalysed. So it is not necessary to buy more catalyst.
4 Mass of sodamide, NaNH2, that contains 14 tonnes of nitrogen = [23 + 14 + 2(1)] / 14 14 tonnes = 39 tonnes Mass of urea, (NH2)2CO, that contains 14 tonnes of nitrogen = [2(14) + 4(1) + 12+ 16] / 2(14) 14 tonnes = 30 tonnes Thus, urea provide more nitrogen per tonne of fertiliser. 5 Mass of ammonium nitrate, NH4NO3, that contains 56 tonnes of nitrogen = [2(14) + 4(1) + 3(16)] / 2(14) 56 tonnes = 160 tonnes

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Ammonia worksheet

  • 1. Chemistry Worksheet Ammonia Suggested Answer Paper 1 Multiple Choice Questions 1. D 2. C 3. B 4. A 5. C 6. B 7. D 8. A 9. C 10. C 11. D 12. A 13. A 14. C 15. B Paper 2 Section A 1(a) 2NH3(g) + CO2(g) CON2H4(s) + H2O(l) (b) (i) volume of NH3 / volume of CO2 = 2/1 volume of NH3 = 2 144 dm3 = 288 dm3 (ii) no. of moles of CON2H4 = no. of moles of CO2 = 144/24 = 6 mol mass of CON2H4 = 6 [12 + 16 + 2(14) + 4(1)] = 360 g (c) Ammonium nitrate, NH4NO3 / Ammonium sulfate, (NH4)2SO4 2 (a) Percentage by mass of nitrogen in ammonium nitrate = 2(14) / [2(14) + 4(1) + 3(16)] 100% = 35.0 % (b) Ammonium nitrate increases the nitrogen content of the soil. Plants need nitrogen to build proteins for plant growth, and thus lead to increased yield of crops. (c) (i) Calcium hydroxide is added to neutralise the excess acids in the soil so that crops can grow better. (ii) Calcium hydroxide is an alkali and will react with the ammonium ions in ammonium nitrate, converting it into ammonia gas. The ammonia gas will escape from the soil into the air. Thus, the plants are unable to absorb the nitrogen from the fertiliser. 3 (a) Ca3N2(s) + 6H2O(l) 3Ca(OH)2(s) + 2NH3(g)
  • 2. (b) Calcium reacts with nitrogen according to the equation: 3Ca(s) + N2(g) Ca3N2(s) No.of moles of Ca3N2 produced = 1/3 2 No. of moles of NH3 produced = 1/3 2 2 Thus, mass of NH3 produced = 1/3 4 [14 + 3(1)] = 22.7 g Section B 1(a) (i) N2(g) + 3H2(g) 2NH3(g) (ii) Nitrogen is obtained by the fractional distillation of liquid air. Air is first cooled and compressed into liquid. The liquid air is then heated to separate its components by fractional distillation. The gases in air are distilled in order of their boiling points, and nitrogen is collected at its boiling point of -196属C. (iii) Iron is used as the catalyst. The other conditions used in the Haber process are: (I) a high pressure of 200 atm; and (II) a moderately high temperature of 450属C.. (b) Mass of nitrogen in 1000 kg of the compound = 2(14) / [2(14) + 9(1) + 31 + 4(16)] 1000 kg = 212.12 kg (c) Test 1: Place a piece of damp red litmus paper into each jar. If the gas in the jar turns the damp red litmus paper blue, that jar contains ammonia gas. Test 2: Place a lighted splint into the mouth of each gas jar. If the gas in the jar extinguished the lighted splint with a pop sound, that jar contains hydrogen gas. The gas jar with a gas that has no effect on the damp red litmus paper and extinguished the lighted splint, contains nitrogen gas. 2 (a) (i) Ammonia gas. (ii) (NH4)2SO4(s) + CaO(s) CaSO4(s) + H2O(l) + 2NH3(g)
  • 3. (iii) no. of moles of (NH4)2SO4 = 3.3 / [2(14) + 8(1) + 32 + 4(16)] = 0.025 mol no. of moles of NH3 = 2 0.025 = 0.05 mol volume of NH3 = 0.05 24 dm3 = 1.2 dm3 (b) Blue precipitate formed. The blue precipitate dissolved in excess of ammonia to form a dark blue solution. Ammonia gas dissolved in water to form an alkaline solution (aqueous ammonia): NH3(g) + H2O(l) NH4+(aq) + OH-(aq) Aqueous ammonia contains hydroxide ions. The hydroxide ions will then react with the copper(II) ions (Cu2+), from copper(II) nitrate solution to form a blue precipitate of copper(II) hydroxide. Cu2+(aq) + 2OH-(aq) Cu(OH)2(s) The copper(II) hydroxide reacts with excess ammonia to form a soluble complex ion. 3 (a) (i) Increasing the pressure increases the percentage of nitrogen and hydrogen that reacts to become ammonia. (ii) Increasing the temperature decreases the percentage of nitrogen and hydrogen that reacts to become ammonia. (b) (i) About 22 % (ii) Advantage: At 400属C, the percentage of nitrogen and hydrogen that reacts to become ammonia is greater than at 500属C. So greater amount of ammonia will be produced. Disadvantage: At 400属C, the reaction proceeds slower than at 500属C. (c) (i) In the manufacture of margarine from vegetable oil, the catalyst use is nickel metal. (ii) Catalyst is not used up during the chemical reaction in which they catalysed. So it is not necessary to buy more catalyst.
  • 4. 4 Mass of sodamide, NaNH2, that contains 14 tonnes of nitrogen = [23 + 14 + 2(1)] / 14 14 tonnes = 39 tonnes Mass of urea, (NH2)2CO, that contains 14 tonnes of nitrogen = [2(14) + 4(1) + 12+ 16] / 2(14) 14 tonnes = 30 tonnes Thus, urea provide more nitrogen per tonne of fertiliser. 5 Mass of ammonium nitrate, NH4NO3, that contains 56 tonnes of nitrogen = [2(14) + 4(1) + 3(16)] / 2(14) 56 tonnes = 160 tonnes