When a chemical equation is balanced, it will have a set of whole number coefficients that cannot be reduced to smaller whole numbers. What is the coefficient for O₂ when the following combustion reaction of a hydrocarbon is balanced? ________ C₇H₁₄ + ________ O₂→ ________ CO₂ + ________ H₂O A) 42 B) 21 C) 11 D) 10 E) None of these answers is correct.

Question

Quizplus · Accepted Answer

To balance the equation, we need to count the number of carbon, hydrogen, and oxygen atoms on both sides. Starting with carbon, we have one carbon atom on the left side and one on the right side, so the coefficient for the hydrocarbon must be 1. Next, we count the number of hydrogen atoms. On the left side, we have 17 hydrogen atoms plus 2 from the hydrocarbon, totaling 19 hydrogen atoms. On the right side, we have 12 hydrogen atoms plus 12 from the product water, totaling 24 hydrogen atoms. To balance the hydrogen atoms, we need to multiply the coefficient for water by 2. Finally, we count the number of oxygen atoms. On the left side, we have 12 oxygen atoms from the oxygen gas. On the right side, we have 12 oxygen atoms from the carbon dioxide and 12 oxygen atoms from the water, totaling 24 oxygen atoms. To balance the oxygen atoms, we need to add a coefficient of 12 to the oxygen gas. Therefore, the balanced equation is:

C + 17H2 + 12O2 → CO + 9H2O

The coefficient for the hydrocarbon (which is not explicitly given in the original equation) is 1, which cannot be reduced to a smaller whole number. The coefficient for oxygen gas is 12, which also cannot be reduced. Therefore, the answer is (B) 21.

When a Chemical Equation Is Balanced, It Will Have a Set