Chemistry Test Thermochemistry 2

Question 1

Which thermodynamic quantity represents the heat exchanged at constant pressure?

Accepted Answer

Enthalpy (H)

Answer

Enthalpy (H = U + PV) equals the heat transferred in a constant-pressure process.

Question 2

A reaction has ΔH = +85 kJ/mol. This reaction is best described as:

Accepted Answer

Endothermic and absorbs heat

Answer

A positive ΔH indicates an endothermic reaction that absorbs heat from the surroundings.

Question 3

In a bomb calorimeter experiment, the calorimeter absorbs 4.50 kJ of heat and contains 500 g of water (specific heat 4.18 J/g·°C). What temperature change occurs in the water?

Accepted Answer

2.15 °C

Answer

ΔT = q/(m×c) = 4500 J / (500 g × 4.18 J/g·°C) ≈ 2.15 °C.

Question 4

Hess's Law states that the total enthalpy change of a reaction is:

Accepted Answer

Independent of the pathway taken

Answer

Hess's Law states ΔH is a state function and depends only on initial and final states, not the pathway.

Question 5

Which process has the most negative (most favorable) lattice energy?

Accepted Answer

LiF formation

Answer

LiF has the highest lattice energy because Li⁺ is the smallest cation and F⁻ is the smallest anion, maximizing ion-ion attraction.

Chemistry Practice Test

Chemistry Practice Test

Chemistry Test Thermochemistry 2