Molecular Physics | Thermodynamics Answers

Calculate the energy required in joules to raise the temperature of 450 grams of water from 15°C to 85°C. (The specific heat capacity of water is 4.18 J/g/°C)

If evaporation is a cooling process qnd boiling is a rapid evaporation, is it accurate to say that boiling is a rapid cooñing process? Explain.

Calculate the amount of heat needed to raise the temperature of 2 liter water form 20°C to the building point. The specific heat capacity of water is 4180J/Kg.C°

A large container which has 285 g of water initially at 21 °C is placed in a microwave oven. The
magnetron in the microwave oven can produce 950 W of EM radiation. The microwave is turned
on for 2.5 minutes. Assuming that all the microwave energy is absorbed by the water, how much
water is left in the container?

Use the van der Waals equation and the ideal gas equation, calculate the volume of 1.000 mol of neon gas at a pressure of 500.0 atm and a temperature of 355.0 K. Explain why the two values are different. (For Ne: a = 0.211 L2 atm/mol2 and b = 0.0171 L/mol)

A daredevil is shot out of a cannon at 45.0° to the horizontal with an initial speed of 29.5 m/s. A net is positioned a horizontal distance of 50.5 m from the cannon. At what height above the cannon should the net be placed in order to catch the daredevil?

a) Determine the enthalpy changes, ΔH for the reaction below, given the following reactions and subsequent ΔH values. Please rewrite the amended chemical reaction equation again.

N2H4 (l) + CH4O (l) CH2O (g) + N2 (g) + 3H2 (g)


2NH3 (g) N2H4 (l) + H2 (g) ΔH = 22.5kJ

2NH3 (g) N2 (g) + 3H2 (g) ΔH = 57.5 kJ

CH2O (g) + H2 (g) CH4O (l) ΔH = 81.2 kJ

b) Given that the enthalpy of vaporization for water as below:

H2O (l) H2O (g) ΔH vap = 44.0 kJ mol-1

Calculate enthalpy ΔH for each of the following processes:

i) Evaporating 3.00 moles of water

ii) Evaporating 3.00 grams of water

i) Condensing 20.0 grams of water
(3 Marks)

c) Use the enthalpy of formation data to calculate the enthalpy of the reaction below.

2C2H6 (g) + 7O2 6H2O (g) + 4CO2 (g)

a) A gas is compressed in a reactor from 0.10 m3 to 0.01 m3 at a constant pressure of 2.0 X 105 Pa. Next the gas is heated at constant volume from a pressure of 2.0 X 105 Pa to 2.0 X 105 Pa. Finally, the gas expands isothermally at 126.85 °C back to a volume of 0.01 m3 at 2 X 105 Pa.

(10 Marks)

i) Sketch a PV diagram of the given conditions. Label your diagram accordingly.
(3 Marks)

ii) Determine the work performance per cycle.
(7 Marks)

b) Describe closed, open and isolated systems
(5 Marks)

1kg of a fluid expands reversibly according to a linear law form 4.2 bar to 1.4 bar. The initial and final volume are 0.004 meters cube and 0.02 meters cube. The fluid is then cooled reversibly at constant pressure and finally compressed reversibly according to a law, p-v=constant, back to the initial condition of 42 bar and 0.004 meters cube. Calculate the work done in each process and the network of the cycle. Sketch the cycle on a p-v diagram.