ACS General Chemistry Exam (2026)
– Practice Questions with Answers &
Explanations
The Chemistry ACS General Chemistry Exam typically emphasizes:
• Stoichiometry
• Atomic structure
• Thermochemistry
• Chemical bonding
• Gases
• Equilibrium
• Acids and bases
• Electrochemistry
• Kinetics
• Laboratory concepts
Below is a mixed set of representative ACS-style questions with
explanations.
1. Significant Figures
How many significant figures are in 0.0045600?
A. 3
B. 4
C. 5
D. 6
Answer:
C. 5
,Explanation:
Leading zeros are not significant. Trailing zeros after a decimal are
significant.
0.0045600 → significant digits are:
4, 5, 6, 0, 0 = 5 sig figs.
2. Dimensional Analysis
What is 250 mL in liters?
A. 0.0250 L
B. 0.250 L
C. 2.50 L
D. 2500 L
Answer:
B. 0.250 L
Explanation:
1000 mL=1 L1000 \text{ mL} = 1 \text{ L}1000 mL=1 L
250 mL×1 L1000 mL=0.250 L250 \text{ mL} \times \frac{1 \text{
L}}{1000 \text{ mL}} = 0.250 \text{ L}250 mL×1000 mL1 L=0.250 L
3. Atomic Structure
Which subatomic particle determines the identity of an element?
A. Electron
B. Neutron
, C. Proton
D. Nucleus
Answer:
C. Proton
Explanation:
The atomic number equals the number of protons. Every element has a
unique proton count.
4. Electron Configuration
What is the electron configuration of oxygen?
A. 1s²2s²2p²
B. 1s²2s²2p⁴
C. 1s²2s²2p⁶
D. 1s²2s¹2p⁵
Answer:
B. 1s²2s²2p⁴
Explanation:
Oxygen has atomic number 8 → 8 electrons.
Filling orbitals:
• 1s²
• 2s²
• 2p⁴
– Practice Questions with Answers &
Explanations
The Chemistry ACS General Chemistry Exam typically emphasizes:
• Stoichiometry
• Atomic structure
• Thermochemistry
• Chemical bonding
• Gases
• Equilibrium
• Acids and bases
• Electrochemistry
• Kinetics
• Laboratory concepts
Below is a mixed set of representative ACS-style questions with
explanations.
1. Significant Figures
How many significant figures are in 0.0045600?
A. 3
B. 4
C. 5
D. 6
Answer:
C. 5
,Explanation:
Leading zeros are not significant. Trailing zeros after a decimal are
significant.
0.0045600 → significant digits are:
4, 5, 6, 0, 0 = 5 sig figs.
2. Dimensional Analysis
What is 250 mL in liters?
A. 0.0250 L
B. 0.250 L
C. 2.50 L
D. 2500 L
Answer:
B. 0.250 L
Explanation:
1000 mL=1 L1000 \text{ mL} = 1 \text{ L}1000 mL=1 L
250 mL×1 L1000 mL=0.250 L250 \text{ mL} \times \frac{1 \text{
L}}{1000 \text{ mL}} = 0.250 \text{ L}250 mL×1000 mL1 L=0.250 L
3. Atomic Structure
Which subatomic particle determines the identity of an element?
A. Electron
B. Neutron
, C. Proton
D. Nucleus
Answer:
C. Proton
Explanation:
The atomic number equals the number of protons. Every element has a
unique proton count.
4. Electron Configuration
What is the electron configuration of oxygen?
A. 1s²2s²2p²
B. 1s²2s²2p⁴
C. 1s²2s²2p⁶
D. 1s²2s¹2p⁵
Answer:
B. 1s²2s²2p⁴
Explanation:
Oxygen has atomic number 8 → 8 electrons.
Filling orbitals:
• 1s²
• 2s²
• 2p⁴
