The complete test bank for Chemistry,
Openstax ,2e [2025 updated] Harvard
university
1. The atomic number of an element equals the number of:
a) neutrons
b) b) protons
c) electrons
d) nucleons
Rationale: The atomic number is defined as the number of protons in the
nucleus.
2. Which element has an electron configuration ending in 4s²3d¹?
a) Scandium
b) Titanium
c) c) Calcium
d) Vanadium
Rationale: 4s²3d¹ corresponds to calcium (Z = 20). Scandium is 4s²3d¹⁰.
3. What is the molecular geometry of CH₄?
a) trigonal planar
b) b) tetrahedral
c) trigonal pyramidal
, d) bent
Rationale: CH₄ has four bonded pairs with no lone pairs → tetrahedral.
4. Which of the following is a strong acid?
a) HOAc
b) b) HClO₄
c) H₃PO₄
d) HF
Rationale: Perchloric acid (HClO₄) is a strong acid—fully dissociates in
solution.
5. The molarity of a solution containing 2.50 mol of solute in 500.0 mL
solution is:
a) 1.25 M
b) b) 5.00 M
c) 0.200 M
d) 2.00 M
Rationale: M = mol/V(L) → 2.50 mol / 0.500 L = 5.00 M.
6. In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water from 4.00
moles of H₂?
a) 1.00
b) 2.00
c) c) 4.00
d) 8.00
Rationale: Stoichiometry: 2 mol H₂ → 2 mol H₂O; thus 4 mol H₂ → 4 mol
H₂O.
,7. What is the oxidation state of sulfur in SO₄²⁻?
a) +2
b) +4
c) c) +6
d) +7
Rationale: Summing to –2 total; 4×(–2) + S = –2; S = +6.
8. According to Le Châtelier, adding heat to an exothermic reaction at
equilibrium will:
a) shift right
b) b) shift left
c) no change
d) double the rate
Rationale: Heat is a product → adding pushes equilibrium to reactants
(left).
9. Which gas behaves most ideally under STP?
a) CO₂
b) NH₃
c) H₂O
d) d) He
Rationale: Helium is monatomic with minimal interactions—closest to ideal
gas.
10.The wavelength of a photon with energy 3.31×10⁻¹⁹ J is:
a) 400 nm
b) 500 nm
, c) c) 600 nm
d) 700 nm
Rationale: λ = hc/E → (6.626×10⁻³⁴·3.00×10⁸)/(3.31×10⁻¹⁹) ≈ 600 nm.
11.Which orbital comes next after 3p in Aufbau order?
a) 3d
b) 4s
c) c) 4s
d) 4p
Rationale: After 3p is 4s by Aufbau principle.
12.Which substance is amphoteric?
a) HCl
b) NaOH
c) c) HCO₃⁻
d) CH₃COOH
Rationale: Bicarbonate can act as acid or base → amphoteric.
13.In a galvanic cell, the anode is where:
a) reduction occurs
b) b) oxidation occurs
c) electrons enter
d) salt bridge is located
Rationale: By definition, oxidation happens at the anode.
14.What volume will 1.00 g of O₂ occupy at STP?
a) 0.50 L
b) b) 0.35 L
Openstax ,2e [2025 updated] Harvard
university
1. The atomic number of an element equals the number of:
a) neutrons
b) b) protons
c) electrons
d) nucleons
Rationale: The atomic number is defined as the number of protons in the
nucleus.
2. Which element has an electron configuration ending in 4s²3d¹?
a) Scandium
b) Titanium
c) c) Calcium
d) Vanadium
Rationale: 4s²3d¹ corresponds to calcium (Z = 20). Scandium is 4s²3d¹⁰.
3. What is the molecular geometry of CH₄?
a) trigonal planar
b) b) tetrahedral
c) trigonal pyramidal
, d) bent
Rationale: CH₄ has four bonded pairs with no lone pairs → tetrahedral.
4. Which of the following is a strong acid?
a) HOAc
b) b) HClO₄
c) H₃PO₄
d) HF
Rationale: Perchloric acid (HClO₄) is a strong acid—fully dissociates in
solution.
5. The molarity of a solution containing 2.50 mol of solute in 500.0 mL
solution is:
a) 1.25 M
b) b) 5.00 M
c) 0.200 M
d) 2.00 M
Rationale: M = mol/V(L) → 2.50 mol / 0.500 L = 5.00 M.
6. In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water from 4.00
moles of H₂?
a) 1.00
b) 2.00
c) c) 4.00
d) 8.00
Rationale: Stoichiometry: 2 mol H₂ → 2 mol H₂O; thus 4 mol H₂ → 4 mol
H₂O.
,7. What is the oxidation state of sulfur in SO₄²⁻?
a) +2
b) +4
c) c) +6
d) +7
Rationale: Summing to –2 total; 4×(–2) + S = –2; S = +6.
8. According to Le Châtelier, adding heat to an exothermic reaction at
equilibrium will:
a) shift right
b) b) shift left
c) no change
d) double the rate
Rationale: Heat is a product → adding pushes equilibrium to reactants
(left).
9. Which gas behaves most ideally under STP?
a) CO₂
b) NH₃
c) H₂O
d) d) He
Rationale: Helium is monatomic with minimal interactions—closest to ideal
gas.
10.The wavelength of a photon with energy 3.31×10⁻¹⁹ J is:
a) 400 nm
b) 500 nm
, c) c) 600 nm
d) 700 nm
Rationale: λ = hc/E → (6.626×10⁻³⁴·3.00×10⁸)/(3.31×10⁻¹⁹) ≈ 600 nm.
11.Which orbital comes next after 3p in Aufbau order?
a) 3d
b) 4s
c) c) 4s
d) 4p
Rationale: After 3p is 4s by Aufbau principle.
12.Which substance is amphoteric?
a) HCl
b) NaOH
c) c) HCO₃⁻
d) CH₃COOH
Rationale: Bicarbonate can act as acid or base → amphoteric.
13.In a galvanic cell, the anode is where:
a) reduction occurs
b) b) oxidation occurs
c) electrons enter
d) salt bridge is located
Rationale: By definition, oxidation happens at the anode.
14.What volume will 1.00 g of O₂ occupy at STP?
a) 0.50 L
b) b) 0.35 L
