Stoichiometry chem

Question

If you have the balanced formula C2H8 + 5 O2 - 3CO2 + 4 H2O, and your perform this reaction and receive 125. moles of water, how many moles of carbon dioxide should you have?

then using the same equation C2H8 + 5 O2 - 3CO2 + 4 H2O. You supply oxygen to this reaction. The oxygen is 2.31 kg of O2. How many grams of C2H8 is needed to react with?

Answer 1

Hello, John,

I will answer the questions based on the assumption you meant to write C3H8, not C2H8 (no such molecule that I'm aware of). The equation isn't balanced for the C2H8, but it works for C3H8.

C3H8 + 5 O2 - 3CO2 + 4 H2O

The first question: To find how many moles of CO₂ we should have if 125 moles of water were produced, the equation tells us the molar ratio between water and CO₂:

(4 moles H₂O)/(3 moles CO₂)

To find the moles CO₂:

(3 moles CO₂)/(4 moles H₂O)* (125 moles H₂O) = 93.75moles CO₂

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Next we are asked how much C₃H₈ do we need for 2.31 kg of O₂. Convert 2.31kg into grams and then divide that by oxygen's molar mass to find the moles O₂ present (72.2 moles). Find the molar ratio of the two compounds:

(1 moles C₃H₈)/( 5 moles O₂)

(1 moles C₃H₈)/( 5 moles O₂)*(72.2 moles O₂) = 14.4 moles C₃H₈

Bob