UNIT 10 COMMON ACIDS AND ALKALIS

Transcription

1 ABLE EDUCATION CENTRE UNIT 10 COMMON ACIDS AND ALKALIS A Multiple-choice questions 1 Which of the following are the properties of alkalis? (1) They taste sour. (2) They are slippery. (3) They can turn red litmus paper blue. (4) They can be used to remove grease. A (1) and (2) only B (2) and (3) only C (1), (3) and (4) only D (2), (3) and (4) only 2 Which of the following is correct? Acid Alkali A Ammonia Sodium hydroxide B Lemon juice Soap solution C Nitric acid Vinegar D Lime water Soft drink 3 What is the colour change if ammonia is dropped on a red litmus paper? A Remains red B From red to blue C From red to orange D From red to blue black

2 4 Which of the following is/are true for both acids and alkalis? (1) They turn red litmus paper blue. (2) They are corrosive. (3) They can change the colour of universal indicator. A (1) only B (2) only C (1) and (3) only D (2) and (3) only 5 Which of the following is incorrect about the approximate ph value of the object? A Stomach juice, ph 2 B Lemon juice, ph 3 C Egg white, ph 11 D Sodium hydroxide, ph 13 6 Which of the following is not a property of acids? A They taste sour. B They react with some metals to give hydrogen gas. C They change blue litmus paper red. D They are slippery. 7 What gas will be given out in the following set- up? delivery tube dilute hydrochloric acid marble chips lime water A Carbon dioxide B Hydrogen C Nitrogen D Oxygen

3 *8 When an egg is put into vinegar, some bubbles appear on the surface of the egg shell. What is the reason for this? A The egg shell is composed of calcium. It reacts with vinegar to give nitrogen. B The egg shell is composed of iron. It reacts with vinegar to give hydrogen. C The egg shell is composed of calcium carbonate. It reacts with vinegar to give carbon dioxide. D The egg shell is composed of sodium carbonate. It reacts with vinegar to give oxygen. 9 What gases in the atmosphere make rainwater acidic? (1) Carbon dioxide (2) Nitrogen (3) Nitrogen oxides (4) Oxygen (5) Sulphur dioxide A (1), (3) and (5) only B (1), (2) and (4) only C (2), (3) and (4) only D (1), (2), (4) and (5) only 10 Which of the following is not an example of neutralization? A Taking antacid when having stomachache. B Putting vinegar on a wound caused by a wasp sting. C Mixing magnesium hydroxide and nitric acid. D Placing a metal into hydrochloric acid. 11 What are the products of the reaction between magnesium hydroxide and nitric acid? A Nitric oxide and water B Magnesium nitrate and water C Nitrogen gas and magnesium D Magnesium chloride and nitrogen dioxide

4 12 Which of the following are the safety measures in handling acids? (1) Wear safety goggles. (2) Add water to acid in the dilution of acid. (3) Put on rubber gloves. A (1) and (2) only B (1) and (3) only C (2) and (3) only D (1), (2) and (3) 13 During neutralization, (1) the ph of the mixture rises. (2) heat is released. (3) cloudy precipitates are formed. (4) salt and water are formed. A (1) and (3) only B (1) and (4) only C (2) and (3) only D (2) and (4) only 14 A blue litmus paper did not change colour after it has been dipped in a solution. This solution can be (1) an acid. (2) an alkali. (3) chemically neutral A (1) and (2) only B (1) and (3) only C (2) and (3) only D (1), (2) and (3)

5 *15 A strong acid of ph 1 is mixed with an alkali of ph 10. Their concentration and volume are the same. The resulting solution will be A acidic. B alkaline. C neutral. D unable to be classified as acidic, alkaline or neutral. 16 Which of the following are the applications of acids? (1) Preserving food (2) Neutralizing alkalis in certain food, e.g. noodle (3) Softening meat A (1) and (2) only B (1) and (3) only C (2) and (3) only D (1), (2) and (3) *17 What acid and alkali should be mixed to prepare potassium sulphate? A Hydrochloric acid and potassium hydroxide B Potassium nitrate and sulphuric acid C Potassium carbonate and nitric acid D Sulphuric acid and potassium hydroxide 18 Which of the following are the applications of alkalis? (1) Neutralizing acid in the stomach (2) Preserving food (3) Softening meat A (1) and (2) only B (1) and (3) only C (2) and (3) only D (1), (2) and (3)

6 19 Which food should not be cooked with a metal pot? A Rice B Potato and beef C Fish D Vinegar, ginger and pork 20 The following is a ph scale. Which letter indicates the ph of table salt? 2 A 6 B C D 10

7 B True or false questions 1 When an acid is added to lime stone, hydrogen gas will be given out. 2 Litmus solution can show the ph value of an acid or an alkali. 3 Zinc can react with dilute sodium hydroxide solution to give out hydrogen gas. *4 Rain water collected from area without any air pollution should be neutral. 5 Acids can preserve food while alkalis cannot. 6 The acidity of an acid can be shown by its ph value. *7 Soft drinks can turn blue litmus paper red. 8 Chlorine gas will be given out when hydrochloric acid is poured onto marble chips. 9 Heat is being absorbed during neutralization. 10 If some acid is splashed on our body, we should wash the affected area with alkali.

8 C Fill-in-the-blanks 1 We take antacid to the excess acid in our stomach. 2 Lemon juice turns blue solution red and its ph is less than. 3 The higher the ph value of a substance, the more it is. 4 Acids can react with metals and carbonates to give out gas and gas respectively. 5 Buildings and statues which are made of can be corroded by acid rain. 6 We may add a few drops of to show the ph value of a solution. 7 Many contain acids or alkalis for removing dirt and greases. 8 Sodium hydroxide solution reacts with to form sodium chloride and water. 9 We use the with a range of 0 to 14 to show the degree of acidity or the degree of of a substance. 10 Acids and alkalis are. We should wear rubber gloves when using them.

9 D Short questions 1 Match the body parts in the left column with their corresponding ph values in the right column. (a) Blood (1) ph 2 (b) Intestinal juice (2) ph 5.5 (c) Skin (3) ph 7.4 (d) Stomach juice (4) ph What should we do if we spill some acids onto our body during an experiment? *3 An egg shell contains calcium carbonate and it is hard. Suggest and explain how you could make the egg shell soft.

10 *4 Connie is going to neutralize some dilute hydrochloric acid. She adds dilute sodium hydroxide to the acid gradually until the mixture becomes alkaline. Sketch a graph in the following diagram to show how the ph value of the mixture changes with the volume of the sodium hydroxide added. ph value Volume of dilute sodium hydroxide added (cm 3 ) 5 Explain why vinegar can be used to preserve food. 6 Plants do not grow well in acidic soil. What should a farmer do if he wants to test whether the soil of his field is acidic or not? How can he tackle the problem if he finds that the soil is acidic?

11 7 List three safety precautions when handling acids or alkalis. *8 Briefly explain why some toothpaste is slightly alkaline. 9 Gary says, We may control the problem of acid rain by saving electricity. Comment on his statement. 10 Give two food examples in which a natural alkali, lye ( 鹼水 ), is added.

12 E Long questions *1 Dilute sodium hydroxide is added gradually to dilute hydrochloric acid until the mixture becomes alkaline. The relationship between the ph value of the mixture and the volume of sodium hydroxide added is shown in the figure below. ph value Volume of sodium hydroxide added (cm 3 ) a b c d Write a word equation for the reaction between dilute sodium hydroxide and dilute hydrochloric acid. What type of reaction is (a)? What is the volume of the dilute sodium hydroxide needed to complete the reaction in (b)? In addition to the ph value of the mixture, which property of the mixture also changes throughout the experiment?

13 2 Hydrochloric acid and sodium hydrogencarbonate (an alkali) are two juices secreted from our digestive system. a Which juice above is secreted from the stomach and from the small intestine respectively? b Write a word equation for the reaction between hydrochloric acid and sodium hydrogencarbonate. c What is the term for the reaction in (b)?

14 *3 Some hydrochloric acid is added to some zinc strips in a test- tube. The test- tube is connected to a syringe which collects the gas given out. hydrochloric acid zinc strips a b c d What gas will be collected by the syringe? Write a word equation for the reaction between the zinc strips and hydrochloric acid. How can you measure the rate of the above reaction? State a method that can increase the rate of the above reaction.

15 4 The fumes from the burning of fossil fuels contain different acidic gases. The following diagram shows a design to remove the acidic gases in the fumes. gas pipe treated fumes untreated fumes gas bubbles treatment tank solution X a Give three acidic gases in the fumes produced from the burning of fossil fuels. b What is the importance of removing acidic gases from the fumes? c Suggest a chemical for solution X.

16 d e A chemical reaction takes place in the treatment tank to remove acidic gases from the fumes. What is the term for the reaction? Besides acidic gases, name one air pollutant in the fumes that may also be removed by this method. *5 Acid rain is caused by the release of acidic gases, e.g. sulphur dioxide, into the atmosphere. Acid rain damages forests and the map below shows the percentage of forests damaged by acid rain in some provinces of a country. A 12% C E 33% N B 8% 24% D 17% F 23% a b c Suggest the major source of sulphur dioxide. Give another acidic gas that can lead to the formation of acid rain. Besides damaging forests, give two more harmful effects of acid rain.

17 d In most of the time, south- westerly wind blows across these provinces, and the areas of forests in these provinces are similar. Explain briefly why province E has a rather high percentage of forest loss.