Final answer:
When a truck that averages 18 miles per gallon travels 197 miles, approximately 205.1 pounds of CO2 are emitted, computed using the factor-of-three ratio and density of gasoline.
Step-by-step explanation:
To calculate how many pounds of carbon dioxide (CO₂) are emitted when a truck that averages 18 miles per gallon travels 197 miles, we first need to determine the amount of gasoline used and then use a conversion factor to convert gasoline to CO₂ emissions.
Firstly, calculate the gallons of gasoline used:
197 miles ÷ 18 miles/gallon = 10.94 gallons.
Next, we use the 'factor-of-three' ratio which states that the mass of CO₂ produced is roughly three times the mass of the gasoline consumed.
Since gasoline has a density of 0.75 kg/L, and there are 3.78541 liters in a gallon, we calculate the mass of gasoline used in kilograms:
10.94 gallons × 3.78541 L/gallon × 0.75 kg/L = 31.01 kg of gasoline.
Therefore, the mass of CO₂ produced is 3 × 31.01 kg = 93.03 kg of CO₂.
To convert kilograms to pounds, we use the conversion factor 1 kg = 2.20462 pounds:
93.03 kg × 2.20462 pounds/kg = 205.1 pounds.
Thus, when the truck travels 197 miles, approximately 205.1 pounds of CO₂ are emitted into the atmosphere, rounded to the nearest tenth of a pound.