MTTC MTTC Chemistry 2 — Questions and Answers
Question 1: In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?
- 2
- 4 (Correct answer)
- 8
- 1
Correct answer: 4
The molar ratio of H₂ to H₂O is 2:2 (1:1), so 4 moles of H₂ produces 4 moles of H₂O.
Question 2: What is the molarity of a solution prepared by dissolving 2 moles of NaCl in enough water to make 500 mL of solution?
- 1 M
- 4 M (Correct answer)
- 0.25 M
- 2.5 M
Correct answer: 4 M
Molarity = moles ÷ liters = 2 mol ÷ 0.5 L = 4 M.
Question 3: According to Le Chatelier's principle, if pressure is increased on a gaseous equilibrium system, the reaction shifts toward:
- The side with more moles of gas
- The side with fewer moles of gas (Correct answer)
- Neither side; pressure has no effect
- Always toward the products
Correct answer: The side with fewer moles of gas
Increasing pressure shifts equilibrium toward the side with fewer moles of gas to partially relieve the stress.
Question 4: Which type of chemical reaction is represented by: A + BC → AC + B?
- Synthesis
- Decomposition
- Single replacement (Correct answer)
- Double replacement
Correct answer: Single replacement
This is a single replacement reaction where element A displaces element B from compound BC.
Question 5: What is the standard enthalpy of formation (ΔHf°) for a pure element in its most stable state at standard conditions?
- 100 kJ/mol
- −100 kJ/mol
- 0 kJ/mol (Correct answer)
- It varies by element
Correct answer: 0 kJ/mol
By definition, the standard enthalpy of formation for any element in its most stable form at standard conditions is exactly zero.
Question 6: Which of the following best describes an exothermic reaction?
- The reaction absorbs energy from the surroundings
- The reaction releases energy to the surroundings (Correct answer)
- The enthalpy change equals zero
- The reaction only proceeds at high temperatures
Correct answer: The reaction releases energy to the surroundings
An exothermic reaction releases energy (heat) to the surroundings and has a negative enthalpy change (ΔH < 0).
Question 7: In a balanced chemical equation, the law of conservation of mass requires that:
- The number of molecules is equal on both sides
- The number of atoms of each element is equal on both sides (Correct answer)
- The volume of products equals the volume of reactants
- The energy of reactants equals the energy of products
Correct answer: The number of atoms of each element is equal on both sides
Conservation of mass means atoms cannot be created or destroyed; the count of each element must be equal on both sides of the equation.
MTTC MTTC Chemistry 2
In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?