PI B

The enthalpy of fusion of methanol (CH3OH) is 3.16 kJ/mol. How much heat would be absorbed or released upon freezing 25.6 grams of methanol?

• 2.52 kJ absorbed

• 0.253 kJ absorbed

• 2.52 kJ released

• 3.95 kJ released

• 3.95 kJ absorbed

A student runs a reaction in a closed system. In the course of the reaction, 64.7 kJ of heat is released to the surroundings and 14.3 kJ of work is done on the system. What is the change in internal energy (∆U) of the reaction?

• -79.0 kJ

• 50.4 kJ

• 79.0 kJ

• -50.4 kJ

• 90.4kJ

Consider the plot below for three different samples of pure water. Based on the plot, which answer choice below is a correct statement regarding the three samples of pure water?

• All three samples have the same heat capacity.

• Sample Z has the greatest heat capacity.

• Sample X has the smallest mass.

• All three samples have different specific heat capacities.

• Sample Y would require the least heat to raise its temperature by 1 K.

A CD player and its battery together do 500 kJ of work, and the battery also releases 250 kJ of energy as heat and the CD player releases 50 kJ as heat due to friction from spinning. What is the change in internal energy of the system, with the system regarded as the battery and CD player together?

• +200 kJ

• -700 kJ

• -750 kJ

• -200 kJ

• -800 kJ

Which of the following is/are a reason that water is a desirable heat sink for use in calorimeters?

I) Water’s heat specific capacity is very precisely known.

II) Water is readily available.

III) Water has an unusually large specific heat capacity.

• I only

• II and III

• I and II

• I, II and III

• II only

Consider a thermodynamic system that is simultaneously releasing heat and doing work. The internal energy of this system will:

• Decrease

• Increase, decrease, or stay the same depending on the magnitudes of heat and work

• Stay exactly the same.

• Increase

The formation of chemical bonds from separated atoms

• is never spontaneous.

• increases entropy.

• may be either endothermic or exothermic.

• is always exothermic.

• is always endothermic.

Which of O2(g), O2(l), H2(g), H2(l), H2O(g), H2O(l) have a standard enthalpy of formation equal to zero?

• O2(g), O2(l), H2(g), H2(l), H2O(g), H2O(l)

• O2(g), H2(g), H2O(g)

• O2(g), O2(l), H2(g), H2(l)

• O2(g), H2(g)

• All of them, but only at absolute zero.

Calculate the heat of formation for 2.6 mol of sulfur dioxide (SO2) from its elements, sulfur and oxygen. Use the balanced chemical equation and the following information.

S(s) + 1.5 O2(g) → SO3(g) ∆H⁰ = −395.2 kJ/mol

2SO2(g) + O2(g) → 2SO3(g) ∆H⁰ = −198.2 kJ/mol

• -414.54

• -562.59

• -384.93

• -769.86

• -592.2

Answer the question below:

• Specific; gram; extensive

• Molar; gram; intensive

• Specific; mole; extensive

• Molar; gram; extensive

• Specific; gram; intensive