Question

1. choose the best answer.

students observe the combustion reaction taking place when they light a propane grill.
which best describes the reactants of the reaction?
oxygen and water
propane and oxygen
carbon dioxide and water
propane and water

1. choose the best answer.

when the following equation is balanced, what is the coefficient for o₂?
fe + o₂ → fe₂o₃
1
2
3
4

Explanation:

Question 5

Combustion reactions involve a fuel (propane, \(C_3H_8\)) reacting with oxygen (\(O_2\)) from the air. Reactants are the substances that react, so propane and oxygen are the reactants. Water and carbon dioxide are products of combustion, not reactants.

Step 1: Write the unbalanced equation

The unbalanced equation is \( \text{Fe} + \text{O}_2
ightarrow \text{Fe}_2\text{O}_3 \).

Step 2: Balance Fe first

On the right, there are 2 Fe atoms. So we put a coefficient of 2 in front of Fe on the left: \( 2\text{Fe} + \text{O}_2
ightarrow \text{Fe}_2\text{O}_3 \).

Step 3: Balance O

On the right, there are 3 O atoms. On the left, there are 2 O atoms. The least common multiple of 2 and 3 is 6. So we put a coefficient of 3 in front of \( \text{O}_2 \) (to get 6 O atoms) and a coefficient of 2 in front of \( \text{Fe}_2\text{O}_3 \) (to get 6 O atoms): \( 2\text{Fe} + 3\text{O}_2
ightarrow 2\text{Fe}_2\text{O}_3 \)? Wait, no, wait. Wait, let's redo. Wait, original right is \( \text{Fe}_2\text{O}_3 \) (3 O). Left is \( \text{O}_2 \) (2 O). So to balance O: multiply \( \text{O}_2 \) by 3 and \( \text{Fe}_2\text{O}_3 \) by 2. Then Fe: on right, 2*2=4 Fe. So left Fe: 4. So balanced equation: \( 4\text{Fe} + 3\text{O}_2
ightarrow 2\text{Fe}_2\text{O}_3 \). So the coefficient for \( \text{O}_2 \) is 3.

Answer:

B. propane and oxygen

Question 6