1. Two manufacturing plants need 1.0e4 kg of Al each week. One plant produces the Al from bauxite (Al2O3), whereas the other gets its Al from recycled cans. Given that recovery of recycled Al consumes only 5% of the energy it takes to manufacture Al from bauxite, what is the dollar difference in energy costs for the two plants? For this problem you should only consider the Al energy costs. Assume each company pays $0.04 per kwhr and the ΔHf for Al2O3 is -1676 kj/mole. Finally, you will need this conversion factor: 1 watt-hr = 3600 joules.
A. $163,928.
B. $6902.
C. $6557.
D. $3451.
E. $3279.
2. Over the course of a month, a family used 100 gallons of hot water per day. What is this families monthly expenses for water heating? For this problem assume that a month has 30 days, the price of electricity is $0.06 per kwhr, the heat capacity of water is 4.18 J/C*gram, that the water is heated from 20 to 70 C and that the water heater is 100% efficient. You can use the conversion factor from the problem above and you may need to look up other conversion factors.
A. $9.50
B. $22.06
C. $39.71
D. $158.33
E. $661.83