,
, Portage Learning CHEM 103 General
Chemistry I Module 4 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
When balancing the combustion reaction
\(\text{C}_{3}\text{H}_{8}+\text{O}_{2}\rightarrow \text{CO}_{2}+\text{H}_{2}\text{O}\),
what is the correct coefficient for \(\text{O}_{2}\) in the lowest whole-number ratio?
A) 3
B) 4
C) 5
D) 10
Answer: C
Rationale: First, balance the Carbons by placing a 3 in front of \(\text{CO}_{2}\). Next,
balance the Hydrogens by placing a 4 in front of \(\text{H}_2\text{O}\). This gives a total
of 10 Oxygen atoms on the product side (\(3 \times 2 = 6\) from \(\text{CO}_{2}\) and \(4
\times 1 = 4\) from \(\text{H}_2\text{O}\)). To balance the 10 Oxygen atoms on the
reactant side, place a coefficient of 5 in front of \(\text{O}_{2}\).
Question 2
What is the sum of all coefficients when the chemical equation
\(\text{Al}+\text{HCl}\rightarrow \text{AlCl}_{3}+\text{H}_{2}\) is completely balanced
using the lowest whole-number ratio?
A) 11
B) 13
C) 6
D) 9
Answer: B
, Portage Learning CHEM 103 General
Chemistry I Module 4 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
When balancing the combustion reaction
\(\text{C}_{3}\text{H}_{8}+\text{O}_{2}\rightarrow \text{CO}_{2}+\text{H}_{2}\text{O}\),
what is the correct coefficient for \(\text{O}_{2}\) in the lowest whole-number ratio?
A) 3
B) 4
C) 5
D) 10
Answer: C
Rationale: First, balance the Carbons by placing a 3 in front of \(\text{CO}_{2}\). Next,
balance the Hydrogens by placing a 4 in front of \(\text{H}_2\text{O}\). This gives a total
of 10 Oxygen atoms on the product side (\(3 \times 2 = 6\) from \(\text{CO}_{2}\) and \(4
\times 1 = 4\) from \(\text{H}_2\text{O}\)). To balance the 10 Oxygen atoms on the
reactant side, place a coefficient of 5 in front of \(\text{O}_{2}\).
Question 2
What is the sum of all coefficients when the chemical equation
\(\text{Al}+\text{HCl}\rightarrow \text{AlCl}_{3}+\text{H}_{2}\) is completely balanced
using the lowest whole-number ratio?
A) 11
B) 13
C) 6
D) 9
Answer: B
