MTTC Chemistry Flashcards

In the reaction 2H₂ + O₂ → 2H₂O, how many moles of water are produced from 4 moles of H₂?

Answer: 4

The molar ratio of H₂ to H₂O is 2:2 (1:1), so 4 moles of H₂ produces 4 moles of H₂O.

What is the molarity of a solution prepared by dissolving 2 moles of NaCl in enough water to make 500 mL of solution?

Answer: 4 M

Molarity = moles ÷ liters = 2 mol ÷ 0.5 L = 4 M.

According to Le Chatelier's principle, if pressure is increased on a gaseous equilibrium system, the reaction shifts toward:

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.

Which type of chemical reaction is represented by: A + BC → AC + B?

Answer: Single replacement

This is a single replacement reaction where element A displaces element B from compound BC.

What is the standard enthalpy of formation (ΔHf°) for a pure element in its most stable state at standard conditions?

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.

Which of the following best describes an exothermic reaction?

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).

In a balanced chemical equation, the law of conservation of mass requires that:

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.