INTERACTIVE SCIENCE 2B

Transcription

1 INTERACTIVE SCIENCE 2B Workbook Solutions (Enrichment Edition) Chapter 10 COMMON ACIDS AND ALKALIS Part A Sectional Exercise 10.1 Concept checking p True 2. False 3. False 4. False 5. True Multiple choice p A 2. D 3. C 4. B 5. A Fill in the blanks p sour 2. (a) mineral (b) hydrochloric (c) sulphuric 3. properties 4. (a) bitter (b) soapy/slippery 5. (a) sodium (b) potassium (c) corrosive 10.2 Multiple choice p A 2. B 3. C 4. C 5. D 10.1

2 Fill in the blanks p (a) blue litmus (b) red litmus (c) Neutral 2. (a) ph (b) lower (c) higher (d) equals to Matching p.30 (a) --- (iv) (b) --- (i) (c) --- (v) (d) --- (ii) (e) --- (iii) (f) --- (iii) (g) --- (ii) Question p (a) Check the ph value of the liquid soap with a piece of ph paper/a ph meter/universal indicator. (b) Silk Liquid Soap (c) ABC Liquid Soap (d) Silk Liquid Soap has ph value of 5.5 which is the same as the ph of healthy skin. It is less likely to harm our skin. A soap solution is usually quite alkaline and may irritate/harm our skin Concept checking p False 2. True 3. False 4. True 5. True Multiple choice p C 2. A 3. C 4. B 5. D 10.2

3 Matching p.33 (a) --- (iii) (b) --- (ii) (c) --- (i) (d) --- (v) (e) --- (iv) Questions p (a) The gas must not be hydrogen/ must be nitrogen or carbon dioxide. (b) The gas was carbon dioxide. (c) (or other reasonable answers) (d) Calcium carbonate 10.4 Multiple choice p A 2. C 3. D 4. D 5. C Questions p (a) Concentrated sulphuric acid (b) Corrosive/ dehydrating property (c) Wash the affected body part under running water, and take off the clothes immediately. 2. (i) Wear safety spectacles. (ii) Wear a laboratory coat. 10.3

4 (iii) Wear gloves. (iv) Dilute the acid in a fume cupboard. (v) Add the concentrated sulphuric acid slowly to a large amount of water and stir with a glass rod c 10.5 Concept checking p False 2. True 3. False 4. True 5. False Multiple choice p B 2. C 3. D 4. D 5. C Questions p (a) Rain that has a ph value lower than 5.6. (b) Sulphur dioxide and nitrogen oxides (c) Calcium carbonate (d) Calcium carbonate in limestone reacts with acid rain. Calcium carbonate dissolves and gives carbon dioxide during the process. 2. (a) Sulphur (b) (i) Corrode building and structures (ii) Kill fish and plants in lakes and rivers (iii) Slow down plant growth/kill plants and trees (c) (i) Save energy so that less coal and oil products are burnt and a smaller amount of pollutants is released. (ii) Use alternative energy sources that give out a smaller amount of pollutants. (iii) Use high-grade fuels with low sulphur content. (or other reasonable answers) 3. A small amount of vinegar was left in the bottle. The water Annie used to water her plants made the s

5 Multiple choice p D 2. C 3. A 4. B 5. C 6. D 7. A 8. B Questions p (a) Sulphuric acid/hydrochloric acid/nitric acid (or any other strong acids) (b) W and X (c) W or X (d) (i) Y or Z (ii) Neutralisation 2. (a) It was used to show the ph value of the solution. (b) The ph value was 13. (c) (i) The ph value of a neutral solution is 7. (ii) The volume of dilute hydrochloric acid needed is 9.0 cm 3. (iii) Sodium hydroxide + Hydrochloric acid Sodium chloride + Water (iv) Evaporation (v) The product is a white residue/tiny granules. (vi) It is table salt/common salt. (d) (i) The ph value was 2.0. (ii) No, it had a ph value lower than ph 2.0 because when more than 13 cm 3 of it was added, the ph value of the solution dropped further. 3. The medicine must be alkaline as it was used to neutralise the acid in his stomach. It should be weakly alkaline because strongly alkaline substances are corrosive and may hurt the stomach Concept checking p False 2. True 3. False 4. True 10.5

6 5. True Multiple choice p D 2. D 3. D 4. B 5. C Matching p.45 (a) --- (i) (b) --- (iii) (c) --- (ii) Question p.46 (a) It is a strong acid and it can damage the metal kettle. (b) (i) Vinegar/ethanoic acid/lemon juice/citric acid (or other reasonable answers) (ii) It is not harmful to humans. It contains a weak acid that will not damage the metal kettle if used for a short period of time. Calcium carbonate dissolves in the acid present and reacts with it to form harmless products. (any two answers from the above) Part B Integrated Exercise Concept checking p T 2. F 3. T 4. T 5. F 6. F 7. F 8. T 9. F 10. T Multiple choice p

7 1. B 2. A 3. B 4. D 5. C 6. B 7. D 8. D 9. A 10. C 11. A 12. D Questions p (a) A (b) G (c) E (d) F or G (e) Addition of solution A 2. (a) P and T (b) Both Q and R are blue in ammonia. (c) Q is yellow in both acids. S is colourless in both acids. (d) P is yellow in ethanoic acid and in sodium hydroxide. (e) P is red in a solution with a ph value equal to or less than 2. T is yellow in a solution with a ph value in between 2 and 8. If a solution looks red after adding P and yellow after adding T, it means that the solution has a ph value of about (a) W (b) V (c) Z (d) W 4. (a) 10.7

8 (b) (Remove the test tube containing the gas from the set-up in (a).) Put a burning splint near the mouth of the test tube. If the gas burns with a pop sound, it is hydrogen. (c) (i) Hydrogen gas will be given out at a lower rate. (ii) There will be no reaction./there will be no hydrogen or gas collected. 5. (a) Colourless gas bubbles are given out. (b) (i) The lime water turns milky. (ii) The gas released in this experiment is carbon dioxide. (c) Limestone/calcium carbonate/other carbonates (d) Acidic cleaners can damage marble surface by reacting with them and giving out carbon dioxide. 6. (a) Concentrated sodium/potassium hydroxide (b) Corrosive (c) 7. (a) The air in Sai Kung is the least polluted. The ph value of the rainwater sample collected there was 5.5, which is closest to the ph value of 5.6 of clean/normal rain. (b) (i) The air in Tsuen Wan and Causeway Bay is the most polluted. The ph values of the rainwater samples collected in these areas were the lowest among the areas shown. This means that the rainwater was highly polluted by acidic pollutants/sulphur dioxide and nitrogen oxides and was the most acidic. (ii) Tsuen Wan: factories and motor vehicles (Tsuen Wan is an industrial area with heavy traffic.) 10.8

9 Causeway Bay: motor vehicles (Causeway Bay has heavy traffic.) (c) (i) The rainwater becomes more acidic. (ii) The southern part of Guangdong is heavily polluted with acidic pollutant gases/sulphur dioxide and nitrogen oxides released from the factories and power stations there. When these gases are blown from the north-east to Hong Kong in winter, the rainwater sample collected in Sheung Shui and Sai Kung (located in north-eastern parts of Hong Kong) becomes more acidic and the ph value of rainwater decreases. 8. (a) ph paper/ph meter/universal indicator (b) Salt solution and sugar solution (c) (i) Lemon juice (ii) Caustic soda/sodium hydroxide (d) (i) Orange juice/lemon juice (ii) Washing soda/sodium carbonate (caustic soda/sodium hydroxide should not be used because it is too alkaline and is corrosive.) (e) (i) Oven cleaner/drain cleaner (or other reasonable answers) (ii) The hazard warning label showing corrosive (iii) Wear plastic gloves. (or other reasonable answers) Part C Concept Map p < 8. (a) sulphur dioxide 14. salt 2. (a) blue (b) red (b) nitrogen oxides 15. spectacles 3. sour 9. vehicles 16. laboratory coat 4. metals 10. < 17. > 5. carbonates 11. corrosion 18. (a) red (b) blue 6. burning 12. crop 19. bitter 7. lime water 13. neutralisation 20. soapy/slippery Part D Reading Comprehension p.59 (a) Sulphuric acid is formed. (b) Coal contains sulphur which reacts with oxygen in air during burning to form sulphur dioxide. (c) During operation, power stations, factories and motor cars are all involved with fuels burning. In addition, at high temperature, some oxygen and nitrogen in air can react to form nitrogen oxides. (d) If we use less energy, a smaller amount of fuels needs to be burnt, and a smaller amount of pollutants/sulphur dioxide and nitrogen oxides will then be given out. 10.9

10 (e) Nitrogen oxides (Carbon monoxide and unburnt petrol do not cause acid rain.) (f) The gas given out in burning is sprayed with lime water before it is released into the air. Most sulphur dioxide is removed by reacting with lime water. (g) Ultra-low sulphur diesel (with only 0.005% sulphur) is used in industries and diesel vehicles. (h) The government, industries and the citizens should work together to control acid rain. Part E Little Einstein s Corner p (a) (i) The hazard warning label corrosive (ii) Clear away the people near the site. (or other reasonable answers) (b) The chemist could collect some water sample from the nearby river and measure its ph value using universal indicator/ph meter/ph paper. If the ph value was lower than normal, acid had leaked into the river. (c) Add limestone (calcium carbonate) or slaked lime (calcium hydroxide) to the river to neutralise the acid. (d) (i) Melt means to change the state from a solid to a liquid. (ii) The correct word should be dissolve. (or other reasonable answers) (e) Hydrogen gas was produced as hydrochloric acid reacted with the iron drain cover. 2. Test (1) Using droppers to add a drop of each of the chemicals to a piece of red litmus paper. (2) Using a spatula, add calcium carbonate powder to each of the test tubes containing the remaining three chemicals. (3) Using droppers to add a few drops of the remaining two chemicals onto a watch glass separately. Heat each of them until the chemical is totally evaporated over a beaker of water bath. Observation and conclusion The liquid that turns the red litmus paper blue is sodium hydroxide solution. The liquid that gives out colourless gas bubbles is hydrochloric acid. Distilled water gives no residue, while sodium chloride solution gives a white powder (i.e. salt). 3. (a) Put some soil into a beaker of water and stir. (b) After the soil has settled, use a dropper to add a drop of the soil water to a piece of ph paper. (c) Compare the colour observed with the colours on the ph colour chart to find out the ph value of the soil water. (d) If the ph value is lower than 7, the soil is acidic. Add small amount amount of 10.10

11 powdered lime to the soil to neutralise it/reduce its acidity/raise its ph value. If the ph value is higher than 7, the soil is alkaline. Add small amount of ammonium sulphate to the soil to neutralise it/reduce its alkalinity/decrease its ph value. (e) Mix the soil and powdered lime or ammonium sulphate thoroughly. (f) Repeat steps (a) to (e) until the soil reaches a ph value of