EmSAT EmSAT Chemistry 4

Question 1

What does Le Chatelier's principle state?

Accepted Answer

A system at equilibrium will shift to counteract a stress applied to it

Answer

Le Chatelier's principle states that if a stress (change in concentration, temperature, or pressure) is applied to a system at equilibrium, the system will shift in the direction that partially counteracts that stress.

Question 2

What is the Kc expression for: N₂ + 3H₂ ⇌ 2NH₃?

Accepted Answer

Kc = [NH₃]² / [N₂][H₂]³

Answer

Kc = [products]^coefficients / [reactants]^coefficients = [NH₃]² / ([N₂][H₂]³). Each concentration is raised to the power of its stoichiometric coefficient.

Question 3

What is an endothermic reaction?

Accepted Answer

A reaction that absorbs heat from the surroundings

Answer

An endothermic reaction absorbs heat energy from the surroundings. The products have higher energy than the reactants, and the enthalpy change (ΔH) is positive.

Question 4

What is enthalpy (H) in thermodynamics?

Accepted Answer

The heat content of a system at constant pressure

Answer

Enthalpy is the heat content of a thermodynamic system at constant pressure. The change in enthalpy (ΔH) indicates whether a reaction releases (exothermic) or absorbs (endothermic) heat.

Question 5

What is Hess's Law?

Accepted Answer

The total enthalpy of a reaction is independent of the pathway

Answer

Hess's Law states that the total enthalpy change for a reaction is the same regardless of whether it occurs in one step or multiple steps. Enthalpy is a state function.

EmSAT Practice Test

EmSAT Practice Test

EmSAT EmSAT Chemistry 4