Question

1. choose the best answer.

what is the balanced equation for the following reaction?
butane (c₄h₁₀) + oxygen →?
○ 2c₄h₁₀ + 13o₂ → 8co₂ + 10h₂o
○ 2c₄h₁₀ + 10o₂ → 8co₂ + 10h₂o
○ c₄h₁₀ + 13o₂ → 8co₂ + 2h₂o
○ c₄h₁₀ + 13o₂ → 4co₂ + 4h₂o

1. match the correct term to complete the sentence.

a(n) reaction releases energy in a chemical reaction.
choices
endothermic
endergonic
exothermic
exergonic

Explanation:

Question 3

Step1: Balance Carbon Atoms

Butane has 4 C atoms. So, in products, \( \text{CO}_2 \) should have 4 C per butane. Let's check each option:

• Option 1: \( 2\text{C}_4\text{H}_{10} \) has 8 C, \( 8\text{CO}_2 \) has 8 C. Good.
• Option 2: \( 2\text{C}_4\text{H}_{10} \) has 8 C, \( 8\text{CO}_2 \) has 8 C. But O balance next.
• Option 3: \( \text{C}_4\text{H}_{10} \) has 4 C, \( 8\text{CO}_2 \) has 8 C. Bad.
• Option 4: \( \text{C}_4\text{H}_{10} \) has 4 C, \( 4\text{CO}_2 \) has 4 C. But H balance next.

Step2: Balance Hydrogen Atoms

Butane has 10 H atoms. So, \( \text{H}_2\text{O} \) should have 10 H (5 molecules, but with coefficient 2 for butane: \( 2\times10 = 20 \) H, so \( \text{H}_2\text{O} \) needs 10 molecules (20 H)).

• Option 1: \( 10\text{H}_2\text{O} \) has 20 H. Good.
• Option 2: \( 10\text{H}_2\text{O} \) has 20 H, but O balance?
• Option 3: \( 2\text{H}_2\text{O} \) has 4 H. Bad.
• Option 4: \( 4\text{H}_2\text{O} \) has 8 H. Bad.

Step3: Balance Oxygen Atoms

Left side: \( \text{O}_2 \) molecules. Right side: \( \text{CO}_2 \) (2 O each) and \( \text{H}_2\text{O} \) (1 O each).

• Option 1: \( 8\text{CO}_2 \) has \( 8\times2 = 16 \) O, \( 10\text{H}_2\text{O} \) has 10 O. Total O: 26. Left: \( 13\text{O}_2 \) has \( 13\times2 = 26 \) O. Balanced.
• Option 2: \( 8\text{CO}_2 \) (16 O) + \( 10\text{H}_2\text{O} \) (10 O) = 26 O. Left: \( 10\text{O}_2 \) has 20 O. Not balanced.

An exothermic reaction releases energy (heat/light) in a chemical reaction. Endothermic absorbs energy, endergonic (non - spontaneous, absorbs energy), exergonic (spontaneous, releases energy, but for chemical reactions releasing energy, exothermic is the term for heat - related energy release in chemical reactions).

Answer:

\( 2\text{C}_4\text{H}_{10} + 13\text{O}_2
ightarrow 8\text{CO}_2 + 10\text{H}_2\text{O} \) (the first option)

Question 4