Question

What mass of water is formed when 1 mole of methane gas reacts with 2 moles of oxygen under identical conditions in their standard states?

• A. 27 g
• B. 18 g
• C. 36 g
• D. 54 g

Hint:

The mass of water formed in a combustion reaction is determined by the stoichiometry of the reaction and the molar mass of water.

Answer 1

The Correct Option is C

Step 1: Understanding the reaction.
The balanced chemical equation for the combustion of methane is: \[ \text{CH}_4 + 2 \, \text{O}_2 \rightarrow \text{CO}_2 + 2 \, \text{H}_2O \] From the equation, we see that 1 mole of methane produces 2 moles of water. The molar mass of water (\( H_2O \)) is 18 g/mol, so the mass of water produced is: \[ \text{Mass of water} = 2 \, \text{moles} \times 18 \, \text{g/mol} = 36 \, \text{g} \] Step 2: Analyzing the options.
(A) 27 g: Incorrect. This is not the correct mass of water formed.
(B) 18 g: Incorrect. This would correspond to 1 mole of water, not 2 moles.
(C) 36 g: Correct — The correct mass of water formed is 36 g.
(D) 54 g: Incorrect. This is not the correct mass.
Step 3: Conclusion.
The correct answer is (C) 36 g, as this is the mass of water formed in the reaction.