Example Problem with Complete Solution

1B-3 : Units and Carbon Dioxide Emissions 4 pts
When a hydrocarbon fuel is burned, almost all of the carbon in the fuel burns completely to form CO2 (carbon dioxide), which is the principle gas causing the greenhouse effect and thus global climate change. On average, 0.59 kg of CO2 is produced for each kW-h of electricity generated from a powerplant that burns natural gas. A typical new household refrigerator uses about 700 kW-h of electricity per year. Determine the amount of CO2 production that is due to the refrigerators in a city with 200,000 households.
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 0.59 kg CO2 / kW-h
N 200000 houses
Power 700 kW-h/house/year
Find : MCO2 ??? mton CO2 / year
Solution : 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.
eqn-1 Eqn 1
Check the units in this equation :
eqn-2
Eqn 2
Plug in the values : MCO2 8.26E+07 kg CO2 / year
Unit conversion factor : 1 metric ton = 1000 kg
Therefore : MCO2 82600 mton CO2 / year
Answers : MCO2 82600 mton CO2 / year