Chemical Reactions and Equations

Which of the following is an example of a redox reaction?

1. CuO + H2 → Cu + H2O
2. NaOH + HCl → NaCl + H2O
3. AgNO3 + NaCl → AgCl + NaNO3
4. CaO + H2O → Ca(OH)2

Which gas turns lime water milky?

1. Oxygen
2. Hydrogen
3. Carbon dioxide
4. Nitrogen

Which type of reaction occurs when electricity breaks water into hydrogen and oxygen?

1. Combination
2. Electrolytic decomposition
3. Displacement
4. Neutralisation

In a chemical reaction, the total mass of reactants is equal to:

1. Mass of products
2. Volume of products
3. Number of molecules only
4. Temperature of reaction

Which substance is responsible for the green coating on copper?

1. Copper oxide
2. Copper carbonate
3. Iron oxide
4. Zinc oxide

Which reaction is used in respiration?

1. Combination reaction
2. Oxidation reaction
3. Displacement reaction
4. Double displacement reaction

Which symbol is used to represent a gas produced in a chemical equation?

1. (s)
2. (l)
3. (g)
4. (aq)

Which of the following reactions represents decomposition?

1. CaCO3 → CaO + CO2
2. H2 + Cl2 → 2HCl
3. Zn + CuSO4 → ZnSO4 + Cu
4. AgNO3 + NaCl → AgCl + NaNO3

What is the colour of copper sulphate solution?

1. Green
2. Blue
3. Yellow
4. White

The reaction between sodium sulphate and barium chloride is an example of:

1. Combination reaction
2. Displacement reaction
3. Double displacement reaction
4. Decomposition reaction

A reaction in which heat is absorbed is called:

1. Exothermic reaction
2. Endothermic reaction
3. Displacement reaction
4. Neutralisation reaction

Which of the following is a balanced chemical equation?

1. H2 + O2 → H2O
2. H2 + O2 → 2H2O
3. 2H2 + O2 → 2H2O
4. H2 + 2O2 → H2O

Which gas is released when zinc reacts with dilute hydrochloric acid?

1. Oxygen
2. Hydrogen
3. Carbon dioxide
4. Nitrogen

The reaction CaO + H2O → Ca(OH)2 is an example of:

1. Decomposition reaction
2. Combination reaction
3. Displacement reaction
4. Double displacement reaction

Which of the following is an example of a chemical change?

1. Melting of ice
2. Cutting of paper
3. Rusting of iron
4. Boiling of water

Why is balancing chemical equations important in chemical calculations?

1. It changes the products formed
2. It ensures accurate stoichiometric relationships
3. It increases reaction speed
4. It reduces energy consumption

In a redox reaction, oxidation and reduction occur:

1. Separately
2. Simultaneously
3. One after another
4. Only in acids

Which process is responsible for rusting of iron?

1. Reduction
2. Oxidation
3. Neutralization
4. Sublimation

Which of the following is an example of a displacement reaction?

1. 2Mg + O₂ → 2MgO
2. Zn + CuSO₄ → ZnSO₄ + Cu
3. CaCO₃ → CaO + CO₂
4. H₂ + Cl₂ → 2HCl

What is oxidation?

1. Gain of oxygen or loss of hydrogen
2. Gain of hydrogen only
3. Loss of oxygen
4. No chemical change

Which reaction involves the breakdown of a compound into simpler substances?

1. Combination reaction
2. Displacement reaction
3. Decomposition reaction
4. Neutralization reaction

What type of reaction is represented by A + B → AB?

1. Decomposition reaction
2. Combination reaction
3. Displacement reaction
4. Redox reaction

Why are chemical equations balanced?

1. To make them look attractive
2. To follow the law of conservation of mass
3. To increase the speed of reaction
4. To reduce reactants

Which of the following indicates that a chemical reaction has occurred?

1. Change in temperature
2. Formation of a precipitate
3. Evolution of gas
4. All of these

What is a chemical reaction?

1. A change in the shape of an object
2. A process in which new substances are formed
3. A change in size only
4. A physical change without new substances