Chemical Reactions and Equations quiz

When a cleaned magnesium ribbon is burnt in air, the white powder formed is:

Which gas is evolved when zinc granules react with dilute sulphuric acid?

The reaction 2AgCl(s) -> 2Ag(s) + Cl2(g), which takes place in sunlight, is an example of:

The reaction Fe2O3 + 2Al -> Al2O3 + 2Fe is an example of:

In the electrolysis of water, the ratio of the volume of hydrogen to the volume of oxygen collected is:

Which of the following is an endothermic reaction?

When lead nitrate solution is mixed with potassium iodide solution, the yellow precipitate formed is:

In the reaction CuO + H2 -> Cu + H2O, the substance that gets oxidised is:

Which of the following chemical equations is correctly balanced?

When green crystals of ferrous sulphate are heated strongly in a dry boiling tube, the colour of the residue left behind is:

Why should a magnesium ribbon be cleaned with sandpaper before it is burnt in air? Write the balanced chemical equation for its burning. (2 marks)

What is meant by a balanced chemical equation? Which law makes it necessary to balance chemical equations? (2 marks)

Why is respiration considered an exothermic reaction? Write the chemical equation for the oxidation of glucose in our body cells. (2 marks)

Write the balanced chemical equation with state symbols for the following: solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and a solution of sodium chloride. (2 marks)

An iron nail is dipped in copper sulphate solution for about 20 minutes. State two observations and write the balanced chemical equation for the reaction. (2 marks)

Why are decomposition reactions called the opposite of combination reactions? Support your answer with one balanced equation of each type. (2 marks)

Distinguish between an exothermic reaction and an endothermic reaction, giving one example of each. (2 marks)

Why is silver chloride stored in dark-coloured bottles? Write the balanced chemical equation for the reaction involved. (2 marks)

What is rancidity? Suggest two methods to prevent it. (2 marks)

In the reaction MnO2 + 4HCl -> MnCl2 + 2H2O + Cl2, identify the substance oxidised and the substance reduced, giving a reason for each. (2 marks)

Balance the following chemical equations: (i) Al + O2 -> Al2O3 (ii) Na + H2O -> NaOH + H2 (iii) KClO3 -> KCl + O2 (3 marks)

Propane (C3H8), a component of LPG, burns completely in oxygen to form carbon dioxide and water. Write the balanced chemical equation. How many molecules of oxygen are needed to burn 4 molecules of propane completely, and how many molecules of carbon dioxide are produced? (3 marks)

During the electrolysis of water acidified with a few drops of dilute sulphuric acid, 24 mL of gas is collected at the cathode. What volume of gas is collected at the anode in the same time? Name both gases and write the balanced chemical equation that explains the ratio of their volumes. (3 marks)

When 10.0 g of calcium carbonate is heated strongly until it decomposes completely, 5.6 g of calcium oxide is left behind. Write the balanced chemical equation, calculate the mass of carbon dioxide released, and state the law on which your calculation is based. (3 marks)

Balance the equation BaCl2 + Al2(SO4)3 -> BaSO4 + AlCl3. If 6 formula units of barium chloride react completely with sufficient aluminium sulphate, how many formula units of barium sulphate and of aluminium chloride are formed? (3 marks)

Read the passage and answer the questions. Meena added a small amount of quicklime (calcium oxide) to water in a beaker. The reaction was vigorous, a hissing sound was heard and the beaker became very hot. The clear solution of slaked lime formed was used for whitewashing a wall. After two to three days, the wall developed a shiny white finish. (i) Write the balanced chemical equation for the reaction of quicklime with water and classify the reaction on two different bases. (ii) Explain, with a balanced chemical equation, why the whitewashed wall develops a shiny finish after two to three days. (iii) Quicklime is manufactured by heating limestone. Write the equation for this reaction and explain how it differs from the reaction in (i) in terms of energy. (5 marks)

Read the passage and answer the questions. In a school laboratory, Arjun heated about 2 g of green ferrous sulphate crystals in a dry boiling tube. He noticed that the colour of the crystals changed and a smell of burning sulphur was given off. His friend heated lead nitrate powder in another boiling tube and observed brown fumes. (i) What is the colour and name of the solid residue left in Arjun's boiling tube? (ii) Write the balanced chemical equation for the decomposition of ferrous sulphate and name the type of reaction. (iii) Name the brown fumes observed by his friend and write the balanced chemical equation for the decomposition of lead nitrate. (5 marks)

Read the passage and answer the questions. Riya cleaned two iron nails with sandpaper. She dipped one nail in copper sulphate solution in a test tube for about 20 minutes and kept the other nail aside for comparison. When she took the first nail out, its surface had a brownish coating, and the colour of the solution had also changed. (i) What change in the colour of the copper sulphate solution did Riya observe, and what is the brownish coating on the nail? (ii) Write the balanced chemical equation for the reaction and name the type of reaction. (iii) Would any reaction occur if a copper strip were placed in ferrous sulphate solution? Give a reason based on the relative reactivity of the two metals. (5 marks)

Read the passage and answer the questions. In a coastal town, the iron railings of a building developed a reddish brown, flaky coating within a few months. In the same house, old silver jewellery had turned black and copper vessels had developed a green coating on their surface. (i) Name the process responsible for all these changes and name the reddish brown substance formed on iron. (ii) Name the black coating on silver and the green coating on copper. (iii) Why is this process a serious problem for iron structures? Suggest two methods to prevent it. (5 marks)

Read the passage and answer the questions. Zinc metal is obtained from its oxide by heating zinc oxide strongly with carbon (coke). The reaction is ZnO + C -> Zn + CO. In a similar way, when hydrogen gas is passed over heated copper oxide, the black coating turns brown as copper metal is formed. (i) In the reaction ZnO + C -> Zn + CO, identify the substance oxidised and the substance reduced. (ii) Give a reason for each of your answers in (i) in terms of gain or loss of oxygen. (iii) Why is this reaction called a redox reaction? Write the balanced chemical equation for the reaction of hydrogen with heated copper oxide described in the passage. (5 marks)

Draw a neat labelled diagram of the experimental setup for the electrolysis of water, showing the plastic container, graphite (carbon) electrodes, test tubes filled with water, battery, switch and gas bubbles. Explain why a few drops of dilute sulphuric acid are added to the water, state which gas is collected at each electrode and in what volume ratio, describe a test for each gas, and write the balanced chemical equation, naming the type of decomposition involved. (6 marks)

Draw a labelled diagram of the activity in which zinc granules react with dilute sulphuric acid in a test tube or conical flask, and the gas evolved is tested with a burning matchstick. Write the balanced chemical equation with state symbols, name the type of reaction, state two observations made during the activity, and explain what happens when the burning matchstick is brought near the gas. (6 marks)

What is a double displacement reaction? Explain, with balanced chemical equations and state symbols, what happens when sodium sulphate solution is mixed with barium chloride solution, and when lead nitrate solution is mixed with potassium iodide solution. Draw a labelled diagram of a beaker or test tube showing the formation of a precipitate. Define a precipitation reaction and distinguish between a displacement reaction and a double displacement reaction, giving one example of each. (6 marks)

Draw a labelled diagram showing copper powder being heated in a china dish placed on a wire gauze over a tripod stand and burner. Describe the change in colour of the copper powder and write the balanced equation for the reaction. Explain how the product can be converted back to copper using hydrogen gas, write the equation, and identify the substances oxidised and reduced. Define oxidation, reduction and a redox reaction in terms of the gain or loss of oxygen or hydrogen. (6 marks)

Draw a labelled diagram showing the heating of lead nitrate powder in a boiling tube held with a test tube holder over a burner, and indicate the brown fumes evolved. Write the balanced chemical equation for this reaction and state two observations. Then explain thermal, electrolytic and photolytic decomposition reactions with one balanced chemical equation for each, and state one use of the decomposition of silver bromide in daily life. (6 marks)