CHEM 1011 Final Exam| 151 Questions| With Complete Solutions

CHEM 1011 Final Exam| 151 Questions| With
Complete Solutions
 Course
 CHEM 1011

Question 1: Atomic Structure
Q: What is the electron configuration of a neutral phosphorus atom? How many unpaired
electrons are in its ground state?
A:
Phosphorus (P) has an atomic number of 15.
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p³
There are 3 unpaired electrons in the 3p orbital.



Question 2: Stoichiometry
Q: How many grams of CO₂ are produced from the complete combustion of 50.0 g of CH₄?
Balanced equation: CH₄ + 2O₂ → CO₂ + 2H₂O
A:
Molar mass of CH₄ = 16.0 g/mol
Moles of CH₄ = 50.0 g ÷ 16.0 g/mol = 3.125 mol
From the equation: 1 mol CH₄ → 1 mol CO₂
So, 3.125 mol CH₄ → 3.125 mol CO₂
Molar mass of CO₂ = 44.0 g/mol
Mass of CO₂ = 3.125 mol × 44.0 g/mol = 137.5 g



Question 3: Limiting Reagent
Q: Given 5.0 g of hydrogen gas and 20.0 g of oxygen gas, which is the limiting reactant in the
reaction:
2H₂ + O₂ → 2H₂O?
A:
Molar mass of H₂ = 2.0 g/mol → 5.0 g ÷ 2.0 = 2.5 mol
Molar mass of O₂ = 32.0 g/mol → 20.0 g ÷ 32.0 = 0.625 mol
From the equation: 2 mol H₂ reacts with 1 mol O₂
To react with 0.625 mol O₂, we need 1.25 mol H₂
We have 2.5 mol H₂, which is more than 1.25 mol
Limiting reactant = O₂



Question 4: Gas Laws
Q: A 5.00 L container holds a gas at 300 K and 2.00 atm. What would be the pressure if the
temperature is increased to 450 K while keeping the volume constant?
A:

,Use Gay-Lussac’s Law: P₁/T₁ = P₂/T₂
P₂ = (P₁ × T₂) ÷ T₁ = (2.00 × 450) ÷ 300 = 3.00 atm



Question 5: Thermochemistry
Q: A reaction releases 150 kJ of heat. Is this reaction exothermic or endothermic?
A:
Since heat is released, the reaction is exothermic.



Question 6: Molarity
Q: What is the molarity of a solution made by dissolving 10.0 g of NaCl in enough water to
make 500.0 mL of solution?
A:
Molar mass of NaCl = 58.5 g/mol
Moles of NaCl = 10.0 g ÷ 58.5 g/mol = 0.1709 mol
Volume in liters = 500.0 mL ÷ 1000 = 0.500 L
Molarity = 0.1709 mol ÷ 0.500 L = 0.342 M



Question 7: Lewis Structures
Q: Draw the Lewis structure of CO₂ and state its molecular geometry.
A:
CO₂: O=C=O (each oxygen forms a double bond with carbon)
Molecular geometry: Linear, with a bond angle of 180°



Question 8: Equilibrium
Q: In the reaction N₂ + 3H₂ ⇌ 2NH₃, what happens if the pressure is increased?
A:
Increasing pressure shifts the equilibrium to the side with fewer gas molecules.
Reactants: 1 mol N₂ + 3 mol H₂ = 4 mol
Products: 2 mol NH₃
Equilibrium shifts to the right (toward NH₃).



Question 9: Acids and Bases
Q: What is the pH of a 0.001 M HCl solution?
A:
HCl is a strong acid and dissociates completely.

, [H⁺] = 0.001 M
pH = -log[H⁺] = -log(0.001) = 3



Question 10: Redox Reactions
Q: Identify the oxidizing and reducing agents in the reaction:
Zn + Cu²⁺ → Zn²⁺ + Cu
A:
Zn loses electrons → oxidized → reducing agent
Cu²⁺ gains electrons → reduced → oxidizing agent
Reducing agent: Zn
Oxidizing agent: Cu²⁺

Question 11: Periodic Trends
Q: Which element has a higher ionization energy: sodium (Na) or chlorine (Cl)? Explain.
A:
Chlorine has a higher ionization energy because it is further to the right in the periodic table,
meaning it holds its electrons more tightly.
Answer: Cl



Question 12: Empirical Formula
Q: A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. Determine
its empirical formula.
A:
Assume 100 g of compound:
C: 40.0 g ÷ 12.0 g/mol = 3.33 mol
H: 6.7 g ÷ 1.0 g/mol = 6.7 mol
O: 53.3 g ÷ 16.0 g/mol = 3.33 mol
Divide all by the smallest (3.33):
C = 1, H = 2, O = 1
Empirical formula: CH₂O



Question 13: Percent Composition
Q: What is the percent composition of nitrogen in NH₄NO₃?
A:
Molar mass of NH₄NO₃ = 14.0 + (4 × 1.0) + 14.0 + (3 × 16.0) = 80.0 g/mol
Mass of N = 2 × 14.0 = 28.0 g
% N = (28.0 ÷ 80.0) × 100 = 35.0%