Recycling aluminum consumes 95% less energy than refining the ore. Consider a ma

Question

Recycling aluminum consumes 95% less energy than refining the ore. Consider a material that requires a total energy of 100 kWh for refining. If recycling requires 95% less energy compared to refining, the same mass of material can be recycled using 5 kWh of energy because 100 kWh – 95 kWh = 5 kWh. The 95 kWh is the energy saved.

About 17 kWh of electricity is required to refine 1.0 kg of aluminum from its ore (17 kWh/kg). How many million kWh of energy is saved if a plant recycles 70  million kg of aluminum?

Express your answer numerically to two significant figures in million kWh. Since the units are million kWh, you may skip multiplying by 10^6.

Explanation / Answer

m = 1 kg of aluminium requires --> 17 kWh (ORE)

for... recycling:

m = 1 kg of aluminium --> (0.05)(17)= 0.85 kWh --> RECYCLE

find million kWh for:

m = 70 *10^6 kg...

0.85 *( 70 *10^6 ) = 59500000 kWh = 59500000*10^-6 = 59.5 kWh per 709 kg Al

this is 5%

for 95 -->

59.5 /0.05 * 0.95 = 1130.5 million kWh are saved via recycling

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