|1B-3 :||Units and Carbon Dioxide Emissions||4 pts|
|A new, energy-efficient home refrigerator consumes about 350 kW-h of electricity per year. Assume the electricity is generated by burning fossil fuels. When fossil fuels like coal, oil, natural gas and gasoline are burned, most of|
|the carbon in the fuel burns completely to form carbon dioxide (CO2). CO2 is a greenhouse gas that contributes to global warming and that is undesirable. In a typical natural gas power plant, 0.5 kg of CO2 is produced for each|
|kW-h of electricity generated. Consider a city with 500,000 homes with one refrigerator in each home. How much CO2, in metric tons, is produced by the refrigerators in the city in one year?|
|Read:||This problem is all
about unit conversions.
Keep careful track of units and it will not be difficult.
A kW-h is unit of energy. A Watt is energy per time and when you multiply by hours (time) you are left with units of energy. A kW-h is kW times hours. It is the amount of energy consumed in an hour by a device that uses 1 kW of power (1 kJ/s for 3600 sec).
|Given:||mCO2||0.5||kg CO2 / kW-h||Power||350||kW-h/house/year|
|Find:||MCO2||???||mton CO2 / year|
|Equations / Data / Solve:|
|The total mass of CO2 produced per year is the product of the rate of CO2 production per kW-h, the rate at which power is used by each house and the number of houses.|
|Check the units in this equation :|
|Plug in the values :||MCO2||8.75E+07||kg CO2 / year|
|Unit conversion factor :||1 metric ton =||1000||kg|
|Therefore :||MCO2||87500||mton CO2 / year|
|Answers:||MCO2||87500||mton CO2 / year|