Name: ( ) Class: Date: F2 I.S. Remedial programme Problem set 09/10 Score: / 30 Concept-checking exercise Study the lecture notes and the textbook, and then answer the following questions. True or false Write down T for true statement, F for wrong statement. 1. Hydrochloric acid is one of the most commonly used acids in the laboratory. 2. Some natural substances show different colours in acids or alkalis. They can be used as acid-alkali indicators. 3. An increase in ph value of a substance means an increase in its acidity. 4. The ph value of orange juice is lower than that of stomach acid. 5. When magnesium ribbons are put into dilute hydrochloric acid, the gas evolved can relight a glowing splint. 6. Salts and water are products formed from the neutralisation of acids and alkalis. 7. People can take antacids to help digestion. 8. The process of adding water into acids or alkalis is called neutralisation. 9. The ph value of acid rain can be as low as 3.0. 10. Acid rain only corrodes buildings. It will not kill living things. 1 2 3 4 5 6 7 8 9 10 Multiple choice Put the best answer in the box provided. 1. Which of the following acids can be found in lemons? (I) Hydrochloric acid (II)Citric acid (III)Ascorbic acid A. (II) only B. (I) and (II) only C. (I) and (III) only D. (II) and (III) only 1
2. Which of the following can turn blue litmus paper red? A. Distilled water B. Dilute hydrochloric acid C. Dilute sodium hydroxide solution D. Sugar solution 3. Which of the following substances is the most acidic? A. A substance having a ph value of 0 B. A substance having a ph value of 1 C. A substance having a ph value of 14 D. A substance having a ph value of 15 4. Distilled water turns ph paper A. red. B. blue. C. yellow. D. green. 5. When dilute hydrochloric acid is added to zinc beads, gas bubbles are evolved. dilute hydrochloric acid zinc beads The gas can A. relight a glowing splint. B. give a pop sound with a glowing splint. C. give a pop sound with a burning splint. D. turn lime water milky. 1 2 3 4 5 2
Short/long questions Write down the answers in the spaces provided 1. Consider the following daily-life products: lemon juice, antacid, oven cleaner, soap solution, orange juice, vinegar (a) Which of the above products is/are acidic? (b) Which of the above products is/are alkaline? 2. Below is a photo of a bottle of sodium hydroxide solution: (a) Is sodium hydroxide solution an acid or an alkali? Suggest ONE simple test to determine its ph value. (b) The following hazard warning label is put on the bottle: What does this hazard warning label mean? 3
3. Below are the photos of four solutions: Concentrated sulphuric acid Fresh milk Lemon juice Glass cleaner (a) Arrange the above four solutions in an ascending order of ph values. (b) (i) Which of the solutions is/are alkaline? (ii) What is the colour change of blue litmus paper in this/these solution(s)? (iii) What is the colour change of red litmus paper in this/these solution(s)? 4
4. Property Acid Alkali Taste (a) (b) Colour change of (c) blue litmus paper (d) Colour change of (e) red litmus paper (f) One example of (g) daily-life products (h) 5. Ben Sir is going to dilute concentrated sulphuric acid by adding water to the acid. water concentrated sulphuric acid (a) What are the potential dangers of this method of diluting a concentrated acid? (b) With the help of a labelled diagram, briefly describe the proper procedures for diluting concentrated acids. 5
Answer Concept-checking exercise 1. Hydrochloric acid is one of the most commonly used acids in the laboratory. (T) 2. Some natural substances show different colours in acids or alkalis They can be used as acid-alkali indicators. ( T) 3. An increase in ph value of a substance means an increase in its acidity. (F) 4. The ph value of orange juice is lower than that of stomach acid. (F) 5. When magnesium ribbons are put into dilute hydrochloric acid, the gas evolved can relight a glowing splint.( F) 6. Salts and water are products formed from the neutralisation of acids and alkalis.( T) 7. People can take antacids to help digestion. ( F) 8. The process of adding water into acids or alkalis is called neutralisation. (F) 9. The ph value of acid rain can be as low as 3.0. (T) 10. Acid rain only corrodes buildings. It will not kill living things. (F) Multiple choice Put the best answer in the box provided. 1. D 2. B 3. A 4. C 5. C Short/long questions Write down the answers in the spaces provided 1. (a) Lemon juice, orange juice and vinegar (b) Antacid, oven cleaner and soap solution (c) Lemon juice and orange juice. The acid contained is citric acid. (d) Oven cleaner (e) Wear protective gloves. 2. (a) Sodium hydroxide solution is an alkali. Its ph value can be tested by using ph paper / universal indicator / ph meter (any one of them). (b) Corrosive 3. (a) Concentrated sulphuric acid < lemon juice < fresh milk < glass cleaner (b) (i) Glass cleaner (ii) It does not change the colour of blue litmus paper. (iii) It turns red litmus paper blue. 4. (a) Sour (b) Bitter (c) From blue to red (d) No colour change (e) No colour change (f) From red to blue (g) Vinegar (or any other reasonable answer) (h) Glass cleaner (or any other reasonable answer) 6
5. (a) Concentrated sulphuric acid reacts with water and give out a lot of heat that may cause it to splash out. (b) glove glass rod water concentrated sulphuric acid Wear safety spectacles, a laboratory coat and gloves. Perform the experiment in a fume cupboard. Add concentrated sulphuric acid slowly to a large amount of water and stir it carefully with a glass rod. 7