Question

Identify the correct coefificients to balance it -C3H8+O2 to -CO2 +-H2O

Answer 1

Answer:

${\rm 1\; C_3H_8} + {\rm 5\; O_2} \to {3\; \rm CO_2} + {4\; \rm H_2O}$.

Explanation:

${\rm ?\; C_3H_8} + {\rm ?\; O_2} \to {?\; \rm CO_2} + {?\; \rm H_2O}$.

Among the four species in this reaction, $\rm C_3H_8$ is species with the largest number of atoms per molecule. Assume that the coefficient of this compound is $1$.

${\rm 1\; C_3H_8} + {\rm ?\; O_2} \to {?\; \rm CO_2} + {?\; \rm H_2O}$.

Number of atoms on the left-hand side of the reaction:

• $\rm C$: $1 \times 3 = 3$.
• $\rm H$: $1 \times 8 = 8$.
• $\rm O$: not found yet.

By the conservation of atoms, the number of atoms on the right-hand side of the reaction should match those on the left-hand side. In this reaction, $\rm CO_2$ is the only product with carbon atoms, whereas $\rm H_2O$ is the only product with hydrogen atoms. These $3$ carbon atoms and $8$ hydrogen atoms would correspond to:

• $3 / 1 = 3$ $\rm CO_2$ molecules, and
• $8 / 2 = 4$ $\rm H_2O$ molecules.

${\rm 1\; C_3H_8} + {\rm ?\; O_2} \to {3\; \rm CO_2} + {4\; \rm H_2O}$.

Number of atoms on the right-hand side of the reaction:

• $\rm C$: $3 \times 1 = 3$.
• $\rm H$: $4 \times 2 = 8$.
• $\rm O$: $3 \times 2 + 4 \times 1 = 10$.

The number of $\rm O$ atoms on the left-hand side should match those on the right-hand side. In this reaction, $\rm O_2$ is the only reactant with $\rm O\!$ atoms. These $10$ $\rm \! O$ atoms would correspond to:

• $5$ $\rm O_2$ molecules.

${\rm 1\; C_3H_8} + {\rm 5\; O_2} \to {3\; \rm CO_2} + {4\; \rm H_2O}$.