Question

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_C3H8(g) + O₂(g) → _H₂O(g) +_CO₂(g)
When the equation for the reaction
represented above is balanced and all
coefficients are reduced to the lowest
whole-number terms, the coefficient for
O₂(g) is
29 A. 1
B. 5
C. 3
D. 2
E. 6

Answer 1

When the combustion equation for propane (C3H8) is balanced, the coefficient for oxygen (O2) is 5. We achieve this by balancing the carbon and hydrogen first and then adjusting the oxygen to fully balance the equation. Therefore, the correct option is B.

Step-by-step explanation:

The balanced equation for the combustion of propane (C3H8) with oxygen (O2) to form water (H2O) and carbon dioxide (CO2) is:

1 C3H8(g) + 5 O2(g) → 4 H2O(g) + 3 CO2(g)

Following the rules of balancing chemical equations, we start by balancing the number of carbon (C) and hydrogen (H) atoms on both sides of the equation, which gives us four H2O molecules and three CO2 molecules. Then, we balance the number of oxygen (O) atoms, which requires five O2 molecules to provide the necessary 10 oxygen atoms (in addition to the two oxygen atoms needed to form the three CO2 molecules). This makes the coefficient for O2(g) 5, which is answer choice B.

Always check your work to make sure that all elements are balanced and that there are no fractional coefficients left in the final equation.