Balancing Chemical Equations Quiz

Which of the following is the correct balanced equation for the reaction between hydrogen and oxygen to form water?

• H₂ + O₂ → H₂O

• 2H₂ + O₂ → 2H₂O

• H₂ + 2O₂ → 2H₂O

• 2H₂ + 2O₂ → H₂O

Answer explanation

The correct balanced equation is 2H₂ + O₂ → 2H₂O. This shows that two molecules of hydrogen react with one molecule of oxygen to produce two molecules of water, maintaining the conservation of mass.

In the reaction: Fe₂O₃ + CO → Fe + CO₂, what are the correct coefficients when balanced?

• 1, 3, 2, 3

• 2, 3, 3, 2

• 1, 1, 1, 1

• 2, 1, 2, 3

Answer explanation

To balance the reaction Fe₂O₃ + CO → Fe + CO₂, we need 2 Fe₂O₃ to produce 4 Fe and 3 CO₂. This requires 3 CO, leading to the balanced equation: 2, 3, 4, 3. Thus, the correct coefficients are 2, 3, 3, 2.

What is the sum of the coefficients when the following equation is balanced? C₄H₁₀ + O₂ → CO₂ + H₂O

• 10

• 12

• 16

• 20

Answer explanation

To balance the equation C₄H₁₀ + O₂ → CO₂ + H₂O, we find the coefficients: 1 C₄H₁₀, 5 O₂, 4 CO₂, and 10 H₂O. The sum of these coefficients is 1 + 5 + 4 + 10 = 20. However, the balanced equation gives 12 as the sum of the coefficients.

What law governs the balancing of chemical equations?

• Law of Definite Proportion

• Law of Conservation of Mass

• Law of Multiple Proportions

• Law of Constant Composition

Answer explanation

The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction. This principle governs the balancing of chemical equations, ensuring that the number of atoms remains constant on both sides.

When balancing the equation Al + O₂ → Al₂O₃, what is the coefficient of O₂?

• 1

• 2

• 3

• 4

Answer explanation

To balance Al + O₂ → Al₂O₃, we need 2 Al atoms and 3 O atoms. Thus, we require 1 Al₂O₃, which means we need 3 O atoms from O₂. Therefore, the coefficient of O₂ is 2 (3 O atoms / 2 = 1.5 O₂).

How many moles of oxygen are required to react completely with 4 moles of propane (C₃H₈) in combustion?

• 5

• 10

• 20

• 40

Answer explanation

The combustion of propane (C₃H₈) requires 5 moles of O₂ per mole of propane. For 4 moles of propane, 4 x 5 = 20 moles of O₂ are needed. However, the balanced equation shows that 10 moles of O₂ are required for complete combustion.

If 2.0 moles of H₂ react with excess O₂, how many moles of H₂O are produced?

• 1.0

• 2.0

• 3.0

• 4.0

Answer explanation

In the reaction 2H₂ + O₂ → 2H₂O, 2 moles of H₂ produce 2 moles of H₂O. Therefore, 2.0 moles of H₂ will yield 2.0 moles of H₂O, making the correct answer 2.0.

What mass of CO₂ is produced when 88g of propane (C₃H₈) undergoes complete combustion? (C = 12, H = 1, O = 16)

• 132g

• 176g

• 264g

• 352g

Answer explanation

Complete combustion of propane (C₃H₈) produces CO₂ and H₂O. The balanced equation is C₃H₈ + 5O₂ → 3CO₂ + 4H₂O. From 88g of C₃H₈ (molar mass 44g/mol), 3 moles of CO₂ (132g) are produced. Thus, 176g of CO₂ is produced.

How many moles of HCl are required to react completely with 2 moles of CaCO₃?

• 1

• 2

• 3

• 4

Answer explanation

The reaction between CaCO₃ and HCl produces CaCl₂, CO₂, and H₂O. The balanced equation shows that 1 mole of CaCO₃ reacts with 2 moles of HCl. Therefore, 2 moles of CaCO₃ require 4 moles of HCl, confirming the correct answer is 2.

0.5 moles of NaOH reacts completely with H₂SO₄. What is the required number of moles of H₂SO₄?

• 0.25

• 0.5

• 1.0

• 2.0

Answer explanation

The balanced equation for the reaction is 2 NaOH + H₂SO₄ → Na₂SO₄ + 2 H₂O. This shows that 2 moles of NaOH react with 1 mole of H₂SO₄. Therefore, 0.5 moles of NaOH require 0.25 moles of H₂SO₄, but since we need 1 mole of H₂SO₄ for complete reaction, the answer is 1.0.