,Question 1
An atom has an atomic number of 15 and a mass number of 31. Determine the exact
number of protons, neutrons, and electrons present in this neutral atom.
A) 15 protons, 15 neutrons, 16 electrons
B) 15 protons, 16 neutrons, 15 electrons
C) 16 protons, 15 neutrons, 16 electrons
D) 31 protons, 15 neutrons, 15 electrons
Answer: B) 15 protons, 16 neutrons, 15 electrons
Rationale: The atomic number always equals the number of protons (15). In a neutral
atom, electrons equal protons (15). The number of neutrons is found by subtracting the
atomic number from the mass number (31 - 15 = 16).
Question 2
Convert a measured temperature of 45.0°C into both Kelvin (K) and Fahrenheit (°F).
A) 318.2 K and 113.0°F
B) 228.2 K and 81.0°F
C) 318.2 K and 57.0°F
D) 273.2 K and 113.0°F
Answer: A) 318.2 K and 113.0°F
Rationale: To convert Celsius to Kelvin: K = °C + 273.15 (45.0 + 273.15 = 318.15,
rounds to 318.2 K). To convert Celsius to Fahrenheit: °F = (°C × 1.8) + 32 = (45.0 × 1.8)
+ 32 = 81 + 32 = 113.0°F.
Question 3
Which of the following experiments or physical phenomena provides the primary
scientific evidence supporting the particle (quantum) nature of light?
A) Light refraction through a glass prism
B) The Photoelectric Effect
C) Double-slit interference patterns
D) Total internal reflection in fiber optics
Answer: B) The Photoelectric Effect
Rationale: The photoelectric effect, explained by Albert Einstein, demonstrates that light
behaves as packets of energy called photons (particles) striking a surface to eject
electrons. Refraction and interference patterns support the wave nature of light.
, Question 4
What is the correct chemical formula for the ionic compound formed between aluminum
ions and sulfate ions?
A) AlSO4
B) Al2SO4
C) Al3(SO4)2
D) Al2(SO4)3
Answer: D) Al2(SO4)3
Rationale: Aluminum forms a fixed cation with a +3 charge (\(Al^{3+}\)). The sulfate
polyatomic ion carries a -2 charge (\(SO_{4}^{2-}\)). To create a neutral compound, the
charges must balance: 2(+3) + 3(-2) = 0, giving \(Al_2(SO_4)_3\).
Question 5
Calculate the molecular weight (molar mass) of calcium phosphate, \(Ca_3(PO_4)_2\),
using the following atomic weights: Ca = 40.08, P = 30.97, O = 16.00 g/mol.
A) 135.05 g/mol
B) 215.21 g/mol
C) 310.18 g/mol
D) 430.42 g/mol
Answer: C) 310.18 g/mol
Rationale: Calculate the sum of all atoms in the formula: Ca = 3 × 40.08 = 120.24 g/mol;
P = 2 × 30.97 = 61.94 g/mol; O = 8 × 16.00 = 128.00 g/mol. Total mass = 120.24 +
61.94 + 128.00 = 310.18 g/mol.
Question 6
How many moles of sugar are present in a 25.0 gram sample of glucose
(\(C_6H_{12}O_6\))? (Molar mass of glucose = 180.16 g/mol)
A) 0.139 moles
B) 4.50 moles
C) 7.21 moles
D) 4,504 moles
Answer: A) 0.139 moles
Rationale: Use the mole calculation formula: Moles = Mass (g) / Molar Mass (g/mol).
Moles = 25.0 g / 180.16 g/mol = 0.13876 moles, which rounds to 0.139 moles using
three significant figures.
Question 7
What is the ground-state electron configuration of a neutral iron (Fe) atom? (Atomic
number = 26)
A) \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4p^{6}\)
An atom has an atomic number of 15 and a mass number of 31. Determine the exact
number of protons, neutrons, and electrons present in this neutral atom.
A) 15 protons, 15 neutrons, 16 electrons
B) 15 protons, 16 neutrons, 15 electrons
C) 16 protons, 15 neutrons, 16 electrons
D) 31 protons, 15 neutrons, 15 electrons
Answer: B) 15 protons, 16 neutrons, 15 electrons
Rationale: The atomic number always equals the number of protons (15). In a neutral
atom, electrons equal protons (15). The number of neutrons is found by subtracting the
atomic number from the mass number (31 - 15 = 16).
Question 2
Convert a measured temperature of 45.0°C into both Kelvin (K) and Fahrenheit (°F).
A) 318.2 K and 113.0°F
B) 228.2 K and 81.0°F
C) 318.2 K and 57.0°F
D) 273.2 K and 113.0°F
Answer: A) 318.2 K and 113.0°F
Rationale: To convert Celsius to Kelvin: K = °C + 273.15 (45.0 + 273.15 = 318.15,
rounds to 318.2 K). To convert Celsius to Fahrenheit: °F = (°C × 1.8) + 32 = (45.0 × 1.8)
+ 32 = 81 + 32 = 113.0°F.
Question 3
Which of the following experiments or physical phenomena provides the primary
scientific evidence supporting the particle (quantum) nature of light?
A) Light refraction through a glass prism
B) The Photoelectric Effect
C) Double-slit interference patterns
D) Total internal reflection in fiber optics
Answer: B) The Photoelectric Effect
Rationale: The photoelectric effect, explained by Albert Einstein, demonstrates that light
behaves as packets of energy called photons (particles) striking a surface to eject
electrons. Refraction and interference patterns support the wave nature of light.
, Question 4
What is the correct chemical formula for the ionic compound formed between aluminum
ions and sulfate ions?
A) AlSO4
B) Al2SO4
C) Al3(SO4)2
D) Al2(SO4)3
Answer: D) Al2(SO4)3
Rationale: Aluminum forms a fixed cation with a +3 charge (\(Al^{3+}\)). The sulfate
polyatomic ion carries a -2 charge (\(SO_{4}^{2-}\)). To create a neutral compound, the
charges must balance: 2(+3) + 3(-2) = 0, giving \(Al_2(SO_4)_3\).
Question 5
Calculate the molecular weight (molar mass) of calcium phosphate, \(Ca_3(PO_4)_2\),
using the following atomic weights: Ca = 40.08, P = 30.97, O = 16.00 g/mol.
A) 135.05 g/mol
B) 215.21 g/mol
C) 310.18 g/mol
D) 430.42 g/mol
Answer: C) 310.18 g/mol
Rationale: Calculate the sum of all atoms in the formula: Ca = 3 × 40.08 = 120.24 g/mol;
P = 2 × 30.97 = 61.94 g/mol; O = 8 × 16.00 = 128.00 g/mol. Total mass = 120.24 +
61.94 + 128.00 = 310.18 g/mol.
Question 6
How many moles of sugar are present in a 25.0 gram sample of glucose
(\(C_6H_{12}O_6\))? (Molar mass of glucose = 180.16 g/mol)
A) 0.139 moles
B) 4.50 moles
C) 7.21 moles
D) 4,504 moles
Answer: A) 0.139 moles
Rationale: Use the mole calculation formula: Moles = Mass (g) / Molar Mass (g/mol).
Moles = 25.0 g / 180.16 g/mol = 0.13876 moles, which rounds to 0.139 moles using
three significant figures.
Question 7
What is the ground-state electron configuration of a neutral iron (Fe) atom? (Atomic
number = 26)
A) \(1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}4p^{6}\)
