Question

1. choose the best answer.

what is likely a reactant in a combustion reaction?
○ light
○ $\ce{c2h4}$
○ heat
○ $\ce{li+}$

1. choose the best answer.

what is always produced during a combustion reaction?
○ metals
○ salts
○ water
○ hydrogen gas

Explanation:

Question 1

Combustion reactions involve a fuel (usually a hydrocarbon) reacting with oxygen. Reactants are substances that participate in the reaction. Light and heat are products or energy changes, not reactants. \( \text{Li}^+ \) is an ion, not a typical combustion reactant. \( \text{C}_2\text{H}_4 \) (ethylene) is a hydrocarbon, a common fuel in combustion.

Combustion of hydrocarbons (or most fuels) produces \( \text{CO}_2 \) and \( \text{H}_2\text{O} \). Metals and salts are not typical combustion products. Hydrogen gas is not always produced; in complete combustion, hydrocarbons form \( \text{CO}_2 \) and \( \text{H}_2\text{O} \). Water is always a product of hydrocarbon combustion (or combustion of substances with hydrogen).

Answer:

B. \( \text{C}_2\text{H}_4 \)

Question 2