Chem Units 3 and 4

Question

A typical passenger vehicle uses about 2.5 x 106 grams of C12H26 per year. How many moles of C12H26 is that? 

Using the last question, how many grams of CO2  could this reaction create under perfect conditions?

Answer 1

Hello, Jay,

A typical passenger vehicle uses about 2.5 x 106 grams of C12H26 per year. How many moles of C12H26 is that? 

We need to convert 2.5x10⁶ grams into moles by dividing by dodecane's molar mass of 170.1 grams/mole. That makes 1.47x10⁴ moles.

Using the last question, how many grams of CO2 could this reaction create under perfect conditions?

We need a balanced equation for the combustion of dodecane to answer this. Balancing this reaction is a bit painful, but I believe this will work:

2 C₁₂H₂₆ + 37 O₂ = 24 CO₂ + 26 H₂O

Please check my numbers. Assuming they are correct, the equatiuon tells us we should expect 24 moles of carbon dioxide for every 2 moles of dodecane, a molar ratio of 24/2 or 12/1.

Take the moles dodecane we found for the first question and multiply by 12 to get the moles CO₂ produced.

(1.47x10⁴ moles dodecane)*(12 moles CO₂/1 mole dodecane) = 1.76x10⁵ moles CO₂.

Multiply moles carbon dioxide times it's molar mass of 44.0 g/mole to yield 7.74x10⁶ grams CO₂.

Bob