Class 10 Science: Chemical Equations — Practice Questions with Answers

Which of the following situations does not involve a chemical reaction?

1. Milk is left open at room temperature during summer
2. Grapes undergo fermentation
3. An iron nail is exposed to a humid atmosphere
4. Glaciers are melting

Select the correct balanced chemical equation that represents the exothermic combustion of natural gas in air.

1. CH₄ + O₂ → CO₂ + 2H₂O
2. CH₄ + 2O₂ → 2CO₂ + 2H₂O + Energy
3. CH₄ + 2O₂ → CO₂ + 2H₂O
4. CH₄ + 2O₂ → CO₂ + 2H₂O + Energy

For the chemical equation pAl + qH₂O → rAl₂O₃ + sH₂, determine the values of the coefficients 'p', 'q', 'r', and 's' that correctly balance the equation.

1. 3, 2, 2, 1
2. 2, 3, 3, 1
3. 2, 3, 1, 3
4. 3, 1, 2, 2

Sodium metal reacts with water to produce sodium hydroxide and hydrogen gas. Select the correctly balanced chemical equation that represents this reaction.

1. Na(s) + 2H₂O(l) → 2NaOH(aq) + 2H₂(g)
2. 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
3. 2Na(s) + 2H₂O(l) → NaOH(aq) + 2H₂(g)
4. 2Na(s) + H₂O(l) → 2NaOH(aq) + 2H₂(g)

Chemical equations must be balanced to adhere to the law of conservation of mass. Which of the following statements about this law is incorrect?

1. The total mass of elements in the reactants equals the total mass of elements in the products.
2. The number of atoms for each element is the same before and after the reaction.
3. The chemical composition of the reactants remains unchanged after the reaction.
4. Mass cannot be created or destroyed during a chemical reaction.

In which of the given processes does the chemical identity of the original substance not change?

1. Curdling of milk
2. Formation of crystals through crystallisation
3. Fermentation of grapes
4. Digestion of food

Consider the following statements: Assertion (A): The equation for the reaction of steam on iron, 3Fe (s) + 4H₂O (g) → Fe₃O₄ (s) + 4H₂ (g), is a balanced chemical equation. Reason (R): A chemical equation must adhere to the law of conservation of mass. Which of the following options is correct?

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

Determine the respective values for the coefficients a, b, c, and d that balance the chemical equation: aPb(NO₃)₂ → bPbO + cNO₂ + dO₂.

1. 1, 1, 2, 1
2. 1, 1, 1, 2
3. 2, 2, 1, 4
4. 2, 2, 4, 1

When 2 mL of sodium hydroxide solution is mixed with a few pieces of granulated zinc in a test tube and warmed, which of the following balanced chemical equations correctly represents the reaction?

1. NaOH + Zn → NaZnO₂ + H₂O
2. 2NaOH + Zn → Na₂ZnO₂ + H₂
3. 2NaOH + Zn → NaZnO₂ + H₂
4. 2NaOH + Zn → Na₂ZnO₂ + H₂O

Determine the values of the coefficients x, y, and z respectively, required to balance the chemical equation: x Zn(NO₃)₂ --(heat)--> y ZnO + z NO₂ + O₂.

1. 4, 2, 2
2. 4, 4, 2
3. 2, 2, 4
4. 2, 4, 2

For the chemical equation: a Al₂O₃ + b HCl → c AlCl₃ + d H₂O, what must be the values of the coefficients a, b, c, and d to balance the equation?

1. a=1, b=6, c=2, d=3
2. a=1, b=6, c=3, d=2
3. a=2, b=6, c=2, d=3
4. a=2, b=6, c=3, d=2