Chemical Changes, Combustion and Reactions Quiz

Consider the following reaction: Fe2O3 + 2Al → 2Fe + Al2O3 In the reaction the role of aluminium is to act as a(n) __________.

1. reducing agent
2. oxidising agent
3. neutralising agent
4. combustion agent

Answer: (a) reducing agent

In a balanced chemical equation, an integer written before the formula of a substance represents the number of molecules or moles involved in the reaction. What are these integers called?

1. Chemical coefficients
2. Thermal coefficients
3. Physical coefficients
4. Stoichiometric coefficients

Answer: (d) Stoichiometric coefficients

In the following question, you will find an assertion and a reason. Select the appropriate option that applies. Assertion (A): Combustion of hydrocarbons produces carbon dioxide and water. Reason (R): Hydrocarbons are organic compounds consisting solely of carbon and hydrogen atoms.

1. Both A and R are true, and R is the correct explanation of A.
2. Both A and R are true, but R is not the correct explanation of A.
3. A is true, but R is false.
4. A is false, but R is true.

Answer: (a) Both A and R are true, and R is the correct explanation of A.

A teacher demonstrates three statements about a chemical reaction between zinc granules and hydrochloric acid: 1. The reaction produces hydrogen gas which can be tested with a ‘pop’ sound. 2. The zinc dissolves, indicating a chemical change has occurred. 3. The test-tube cools down because hydrogen gas absorbs heat during formation. Which of the above statements are correct regarding this reaction?

1. Only 1
2. Only 2
3. Only 2 and 3
4. Only 1 and 2

Answer: (c) Only 2 and 3

When petrol burns in the presence of oxygen inside the engine of a car, carbon dioxide and water are produced, and the temperature inside the engine becomes very high. This reaction powers the car. Based on this, which of the following statements is/are incorrect about the process? A. Light energy triggers the reaction. B. Heat energy is taken out from the surroundings. C. Oxygen and petrol are the reactants in this process.

1. A only
2. A and B only
3. B and C only
4. B only

Answer: (b) A and B only

Which of the following pairs of atoms would require the most energy to break their bond?

Answer: (c)

Which of the following fuels has the highest calorific value?

1. Coal
2. LPG
3. Hydrogen
4. CNG

Answer: (c) Hydrogen

LPG is often considered an efficient domestic fuel compared to wood. Which of the following is a correct explanation for this?

1. LPG has a higher ignition temperature than wood.
2. LPG produces fewer pollutants and has a higher calorific value.
3. Wood burns faster, leading to more wastage.
4. LPG does not form carbon dioxide on combustion.

Answer: (b) LPG produces fewer pollutants and has a higher calorific value.

A diagram of a candle flame shows three distinct zones: outer (blue), middle (yellow), and inner (black). What does the blue zone indicate?

1. Incomplete combustion
2. Presence of unburnt carbon particles
3. Formation of carbon monoxide
4. Complete combustion

Answer: (d) Complete combustion

In an experiment, two paper cups are heated: one is empty, and the other contains water. The empty cup catches fire while the water-filled cup does not. Why does the water-filled cup not burn? A. The ignition temperature of paper increases in the presence of water. B. The heat supplied to the paper cup is absorbed by the water. C. Paper becomes non-combustible in the presence of water. D. Water reduces the calorific value of paper.

1. A and B only
2. B only
3. A and C only
4. B and D only

Answer: (b) B only