AP Chemistry LF5

A sample of CHCl3 (s)was exposed to a constant source of heat for a period of time. The graph above shows the change in the temperature of the sample as heat is added. Which of the following best describes what occurs at the particle level that makes segment D longer than segment B?

• The specific heat capacity of the liquid is significantly higher than that of the solid, because the particles in the liquid state need to absorb more thermal energy to increase their average speed.

• The specific heat capacity of the solid is significantly higher than that of the gas, because the particles in the solid state need to absorb more thermal energy to increase their average speed.

• The enthalpy of fusion is greater than the enthalpy of vaporization, because separating molecules from their bound crystalline state requires more energy than separating molecules completely from the liquid state.

• The enthalpy of vaporization is greater than the enthalpy of fusion, because separating molecules completely from the liquid to form a gas requires more energy than separating molecules from their bound crystalline state to a liquid state.

Tags

NGSS.HS-PS3-4

A 2.00 mol sample of C2H5OH undergoes the phase transition illustrated in the diagram above. The molar enthalpy of vaporization, ΔHvap, of C2H5OH is +38.6kJ/mol. Which of the following best identifies the change in enthalpy in the phase transition shown in the diagram?

• +19.3 kJ

• +77.2 kJ

• -19.3 kJ

• -77.2 kJ

Tags

NGSS.HS-PS1-4

NGSS.HS-PS3-4

2 H2S (g) + 3 02 (g) → 2 H2O (l) + 2 SO2 (g)

ΔH= -1120 kJ/mol rxn

Based on the reaction represented by the chemical equation shown above, what is the amount of heat released when 4.00 mol of H2S (g) reacts with 9.00 mol of O2 (g)?

• -560 kJ

• -1120 kJ

• -2240 kJ

• -3360 kJ

Tags

NGSS.HS-PS3-1