Acids, Bases and Salts quiz

A solution turns red litmus blue. Its pH is likely to be:

Which gas is usually liberated when an acid reacts with a metal?

The chemical formula of bleaching powder is:

Which of the following is an olfactory indicator?

The acid present in the sting of an ant or a nettle leaf is:

Tooth decay starts when the pH of the mouth is lower than:

Plaster of Paris is obtained by heating gypsum at:

Which of the following salts has a pH greater than 7 in aqueous solution?

In the chlor-alkali process, the gas produced at the anode is:

Phenolphthalein turns which colour in a basic solution?

Why do HCl and HNO3 show acidic character in aqueous solutions, while solutions of alcohol and glucose do not? (2 marks)

Why does dry HCl gas not change the colour of dry blue litmus paper? (2 marks)

Why should curd and sour substances not be kept in brass and copper vessels? (2 marks)

What happens when an acid reacts with a metal oxide? Write a balanced equation for the reaction of copper oxide with dilute hydrochloric acid and state the colour change. (2 marks)

Give two uses each of baking soda and washing soda. (2 marks)

Why is the pH of the soil important for plants? How do farmers correct acidic soil? (2 marks)

Explain how an antacid such as milk of magnesia gives relief from indigestion. Write the equation for the reaction. (2 marks)

What will happen if a solution of sodium hydrocarbonate is heated? Give the equation. (2 marks)

What is a family of salts? Name the family to which NaCl and Na2SO4 belong, and the family of K2SO4 and Na2SO4. (2 marks)

Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain. (2 marks)

In the chlor-alkali process, 117 g of sodium chloride is electrolysed in water. Write the balanced equation and calculate the masses of sodium hydroxide, chlorine and hydrogen produced. (Na = 23, Cl = 35.5, O = 16, H = 1) (3 marks)

Calculate the mass of water lost when 172 g of gypsum is heated at 373 K to form plaster of Paris. Write the balanced equation. (Ca = 40, S = 32, O = 16, H = 1) (3 marks)

Blue copper sulphate crystals (CuSO4.5H2O) turn white on heating. Calculate the percentage loss in mass when 24.95 g of the crystals are heated until all the water of crystallisation is removed. (Cu = 63.5, S = 32, O = 16, H = 1) (3 marks)

10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same NaOH solution, how much of the same HCl solution will be required to neutralise it? Explain your reasoning. (3 marks)

A student tests five samples with pH paper: gastric juice pH 1.2, lemon juice pH 2.2, pure water pH 7, blood pH 7.4 and milk of magnesia pH 10. Arrange them in increasing order of OH- ion concentration, and state which of them are acidic, neutral and basic. (3 marks)

Read the passage and answer the questions. Sodium chloride is obtained from sea water by evaporation. It is the raw material for several useful chemicals. When electricity is passed through an aqueous solution of sodium chloride (brine), sodium hydroxide, chlorine and hydrogen are formed. Chlorine is then passed over dry slaked lime to make bleaching powder. (i) Name the process and write the balanced chemical equation for the electrolysis of brine. (ii) Write the equation for the preparation of bleaching powder. (iii) Give two uses of bleaching powder. (5 marks)

Read the passage and answer the questions. Riya was stung by a honeybee while working in the garden. Her mother applied a paste of baking soda on the spot, and the pain reduced. Later, Riya touched the leaves of a nettle plant and felt a burning sensation, which was relieved when the area was rubbed with the leaf of the dock plant. (i) Why did the baking soda paste give relief? Name the type of reaction. (ii) Name the acid in the nettle sting. (iii) Write the chemical name and formula of baking soda and one more use of it in the kitchen. (5 marks)

Read the passage and answer the questions. In an experiment, a student takes four test tubes containing dilute HCl and adds zinc granules to test tube A, sodium carbonate to B, copper oxide to C and sodium hydroxide solution with a drop of phenolphthalein to D. (i) In which test tubes is a gas evolved? Name the gases. (ii) What colour change is seen in test tube C? Write the equation. (iii) What would the student observe in test tube D as HCl is added drop by drop? Explain. (5 marks)

Read the passage and answer the questions. A farmer notices that his crops are not growing well. Testing his field shows that the soil has a pH of 5. An agricultural officer advises him to add a certain substance to the soil before sowing. (i) Is the soil acidic or basic? (ii) Name a substance the farmer could add, and explain how it works. (iii) Why do most plants grow best in soil with pH close to 7? (5 marks)

Read the passage and answer the questions. Washing soda is obtained from sodium chloride through a two-step process: baking soda is first made by the reaction of brine with ammonia and carbon dioxide, and then it is heated to form sodium carbonate, which is recrystallised. (i) Write the equation for the formation of baking soda. (ii) Write the equation for the conversion of baking soda into sodium carbonate on heating. (iii) Write the equation for the recrystallisation of sodium carbonate and give two uses of washing soda. (5 marks)

What is the pH scale? Draw a labelled diagram of the pH scale from 0 to 14, showing the colours of universal indicator and marking the positions of gastric juice, lemon juice, pure water, blood and sodium hydroxide solution. Explain the importance of pH in our digestive system and in tooth decay. (6 marks)

Describe an activity, with a labelled diagram, to show that acids and bases react with metal carbonates or metals. Write balanced equations for the reaction of (i) sodium carbonate with HCl (ii) sodium hydrogencarbonate with HCl (iii) zinc with sodium hydroxide, and explain what happens when excess carbon dioxide is passed through lime water. (6 marks)

Explain, with a labelled diagram of heating copper sulphate crystals in a boiling tube, what water of crystallisation is and how it can be removed and restored. Write the formulae of hydrated copper sulphate, gypsum, washing soda and plaster of Paris. Write the equation for the setting of plaster of Paris with water. (6 marks)

What is the chlor-alkali process? Draw a labelled diagram of the electrolysis of brine showing the anode, cathode, the gases evolved and the product formed near the cathode. Write the balanced equation and give two uses each of sodium hydroxide, chlorine and hydrogen. (6 marks)

Explain the difference between strong and weak acids and between concentrated and dilute acids. Why is diluting an acid an exothermic process, and why must it be done carefully? Draw a diagram showing the correct way to dilute concentrated sulphuric acid, and explain the role of water in the acidic behaviour of HCl. (6 marks)