Which one of the following fuel sources is considered a renewable form of energy?

SDES11-104 Tutorial Test 4 2015

10 Marks

(Use periodic table where necessary)

Q1 (a) what are four forms of kinetic energy?

e.g. mechanical energy, electromagnetic radiation (light), sound, heat energy
(b) Which one of the following fuel sources is considered a renewable form of energy?

A            B               C                D               E                  F

Coal   Shale oil    Natural gas   Uranium     Wood    None of these

Q2. (a) How much heat energy would be produced from completely burning 10 moles of methane in air?
See page 207 textbook. Using CH4 + 2O2 = CO2 + 2H2O  + 890 kJ energy

10 moles methane  =    8,900 kJ       (some selected 803 kJ for heat energy released by combustion reaction from p 172 Text book)

(b) Give a balanced general equation for the conversion of solar energy by plants to chemical energy (sugars). Include reactants and products.

6CO2 + 6H2O + light energy = 6(CH2O) + 6CO2

Q3.  (a) A roof-mounted 3 kW PV system on a house has an average electrical output of 15 kW-h each day. In this case, the annual household use of electricity is 60,000 kW-h . What percentage of household use of electricity would be supplied by this PV system?

9.125%
(b) What is the annual estimated output of electricity (e.g. kW-h or household equivalents) from the demonstration wind turbine at Bond University?

See Plaque near Wind turbine site Bond University

Q4.  (a) What is the difference between nuclear fission and fusion?

See Text Book chapter 10

(b) Write the nuclear reaction for the emission of an alpha particle during the radioactive decay of Uranium -238 to Thorium.

23892 U          234 90 Th = 4 2 He 2+

Q5. (a) What is the half-life of a radioactive isotope that decays to 6.25% of the original amount in 404 days?

101 days

(b) How many kg of carbon dioxide would be emitted to air from burning a tonne of methane gas?

2,750 kg

Q6. (a) What are the typical carbon dioxide emissions in kg from burning one tonne of brown coal?  Use Table 10.7 in Text.

900 kg    read Table 10.7 carefully

(b) A small wind turbine has rotor blades with a diameter of 4 m. If the wind speed blowing through the blades is 10 ms-1 what would the wind power be in kilowatts? (Assume the air density is 1.2 kg m-3)

Equation page 195 and worked example 2 Text Book    7,536 W = 7.54 kW

Q7.  What basic type of system (i.e. open, closed or isolated) best describes the following:

(a) an insulated thermos flask full of hot coffee?

………Isolated……………………

(b) a helium gas-filled balloon?

………Closed…………………

Q8. (a) Which of the following thermodynamic properties are state functions?

A.    Heat
B.    Work
C.    Internal energy
D.    Entropy
E.    Temperature

…………………………………………………………

(b) Which of the following processes are endothermic?

A.    Decomposition of hydrogen peroxide (?H = -98.2 kJ mol-1)
B.    Melting ice cubes into water
C.    Freezing water into ice cubes
D.    Photosynthesis involving sunlight

…………………………………………………………

Q9. (a) A process with a change in entropy of the system (?Ssystem) of 45 J K-1 is observed to be non-spontaneous. What can we deduce about the change in entropy of the surroundings (?Ssurroundings)?

A.    ?Ssurroundings  <  -45 J K-1
B.    ?Ssurroundings  =  -45 J K-1
C.    ?Ssurroundings  >  -45 J K-1
D.    It is not possible to deduce anything about ?Ssurroundings.

…(Equilibrium/reversible cannot be spontaneous in either direction)………………………………………..

(b) What is the only temperature (in K) at which the entropy of a perfect crystalline substance can be said to equal zero?

…………0   K  (Third Law of Thermodynamics)………………………………….

Q10. (a) Consider the following reaction for the industrial production of ammonia gas from nitrogen and hydrogen gas (1 mark):

N2(g) + 3H2(g) ? 2NH3(g)

Using the values in the table below, calculate the total change in enthalpy (?Hreaction) and entropy (?Sreaction) for the production of 200 moles of ammonia gas? (Note: you will first need to balance the reaction)

Compound    ?Hfo
(kJ mol-1)    ?So
(J K-1 mol-1)
N2(g)    0    191.61
H2(g)    0    130.68
NH3(g)    -46.11    192.45

Answers = ?Hreaction  -9,222  kJ                    ?Sreaction  19.875 J K-1

See Worked example for Tute 4 for these types of enthalpy and entropy calculations on iLearn (Tutorials/Assessment).

……………………………………………………..
Optional only – No mark lost for incorrect answer

(b) Using your above answers and the equation for Gibb’s free energy
(?Go = ?Ho – T?So), would the production of ammonia via this reaction likely be:

A.    Spontaneous
B.    Non-spontaneous
C.    It depends on the temperature of the reaction.

…………………………………………………

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