Question

c₃h₈ + 5o₂ → 3co₂ + 4h₂o

• how many atoms of carbon are in the reactant (total)? ________
• how many atoms of hydrogen are in the reactant (total)? ________
• how many molecules of o₂ are in the reactant? ________
• how many total atoms of oxygen are in the reactant?________
• how many molecules of co₂ are in the product? ________
• how many total atoms of carbon are in the product? ________
• how many total atoms of oxygen are in the product (don’t forget that it may be present in more than one compound)? ________
• how many atoms of hydrogen are in the product? ________
• does the number of atoms of each element on the reactant side match that of the product side? ________

Explanation:

Step1: Identify carbon atoms in reactant

In $C_3H_8$, there are 3 carbon atoms and oxygen in $O_2$ has no carbon. So carbon atoms in reactant is 3.

Step2: Identify hydrogen atoms in reactant

In $C_3H_8$, there are 8 hydrogen atoms and oxygen in $O_2$ has no hydrogen. So hydrogen atoms in reactant is 8.

Step3: Identify $O_2$ molecules in reactant

The coefficient of $O_2$ is 5, so there are 5 molecules of $O_2$ in reactant.

Step4: Identify total oxygen atoms in reactant

Each $O_2$ molecule has 2 oxygen atoms, with 5 $O_2$ molecules, so total oxygen atoms are $5\times2 = 10$.

Step5: Identify $CO_2$ molecules in product

The coefficient of $CO_2$ is 3, so there are 3 molecules of $CO_2$ in product.

Step6: Identify total carbon atoms in product

Each $CO_2$ molecule has 1 carbon atom, with 3 $CO_2$ molecules, so total carbon atoms in product is 3.

Step7: Identify total oxygen atoms in product

In 3 $CO_2$ molecules, there are $3\times2 = 6$ oxygen atoms, and in 4 $H_2O$ molecules, there are 4 oxygen atoms. So total oxygen atoms in product is $6 + 4=10$.

Step8: Identify hydrogen atoms in product

In 4 $H_2O$ molecules, there are $4\times2 = 8$ hydrogen atoms.

Step9: Check atom - conservation

Carbon: Reactant has 3, Product has 3. Hydrogen: Reactant has 8, Product has 8. Oxygen: Reactant has 10, Product has 10. So the number of atoms of each element on the reactant side matches that of the product side.

Answer:

• How many atoms of Carbon are in the reactant (total)? 3
• How many atoms of Hydrogen are in the reactant (total)? 8
• How many molecules of $O_2$ are in the reactant? 5
• How many TOTAL atoms of Oxygen are in the reactant? 10
• How many molecules of $CO_2$ are in the product? 3
• How many TOTAL atoms of Carbon are in the product? 3
• How many TOTAL atoms of Oxygen are in the product (don’t forget that it may be present in more than one compound)? 10
• How many atoms of Hydrogen are in the product? 8
• Does the number of atoms of each element on the reactant side match that of the product side? Yes