Question

1. choose the best answer.

what does this reaction indicate?
$\ce{ch_{4}(g) + 2o_{2}(g) \
ightarrow co_{2}(g) + 2h_{2}o(g) + 890\\ kj/mol}$
the reaction rate is slow.
it is an exergonic reaction.
energy is absorbed.
it is an endergonic reaction.

1. choose the best answer.

what is an example of an incomplete combustion reaction?
$\ce{ch_{4}(g) + 2o_{2}(g) \
ightarrow co_{2}(g) + 2h_{2}o(g)}$
$\ce{c_{3}h_{6}o + 4o_{2} \
ightarrow 3co_{2} + 3h_{2}o}$
$\ce{ch_{4} + o_{2} \
ightarrow co + 2h_{2}o}$
$\ce{c + o_{2} \
ightarrow co_{2}}$

Explanation:

Question 7

1. Analyze the reaction equation \( \text{CH}_4(g) + 2\text{O}_2(g)

ightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(g) + 890 \, \text{kJ/mol} \). The positive energy term on the product side means energy is released.

1. Exergonic reactions release energy, endergonic absorb. The reaction rate isn't indicated by energy in the equation. So "It is an exergonic reaction" is correct.

1. Incomplete combustion of hydrocarbons produces carbon monoxide (CO) or carbon (C) instead of \( \text{CO}_2 \).
2. Check each option:

• \( \text{CH}_4(g) + 2\text{O}_2(g)

ightarrow \text{CO}_2(g) + 2\text{H}_2\text{O}(g) \): Complete (produces \( \text{CO}_2 \)).

• \( \text{C}_3\text{H}_6\text{O} + 4\text{O}_2

ightarrow 3\text{CO}_2 + 3\text{H}_2\text{O} \): Complete (produces \( \text{CO}_2 \)).

• \( \text{CH}_4 + \text{O}_2

ightarrow \text{CO} + 2\text{H}_2\text{O} \): Produces CO (incomplete).

• \( \text{C}+\text{O}_2

ightarrow \text{CO}_2 \): Complete (produces \( \text{CO}_2 \)).

Answer:

It is an exergonic reaction.

Question 8