Answer to Question #113455 in Chemistry for Katherine

Question

Balance the following chemical equations. Always show your solution.
1. ____ N 2 O 5  ____ N 2 + ____O 2

2. ____ C 5 H 12 + ____ O 2  ____ CO 2 + ____ H 2 O

3. ____ C 4 H 6 O 3 + ____ H 2 O  ____ C 2 H 4 O 2

Answer 1

Solution:

(1)

First, write the unbalanced equation: N₂O₅ = N₂ + O₂ (unbalanced)

Next, count the number of each type of atom present in the unbalanced equation.

Though nitrogen is balanced, changes in coefficients are needed to balance the number of oxygen atoms. To balance the number of oxygen atoms, a reasonable first attempt would be to change the coefficients for the O₂ and N₂O₅ to integers that will yield 10 O atoms (the least common multiple for the O atom subscripts in these two formulas).

2N₂O₅ = N₂ + 5O₂ (unbalanced)

The N atom balance has been upset by this change; it is restored by changing the coefficient for the reactant N₂ to 2.

2N₂O₅ = 2N₂ + 5O₂

The numbers of N and O atoms on either side of the equation are now equal, and so the equation is balanced.

The balanced chemical equation (1): 2N₂O₅ = 2N₂ + 5O₂

(2)

First, write the unbalanced equation: C₅H₁₂ + O₂ = CO₂ + H₂O (unbalanced)

Next, count the number of each type of atom present in the unbalanced equation.

To balance the number of hydrogen atoms, a reasonable first attempt would be to change the coefficients for the C₅H₁₂ and H₂O to integers that will yield 12 H atoms (the least common multiple for the H atom subscripts in these two formulas).

C₅H₁₂ + O₂ = CO₂ + 6H₂O (unbalanced)

To balance the number of carbon atoms, a reasonable attempt would be to change the coefficients for the C₅H₁₂ and CO₂ to integers that will yield 5 C atoms (the least common multiple for the C atom subscripts in these two formulas).

C₅H₁₂ + O₂ = 5CO₂ + 6H₂O (unbalanced)

The O atom balance is restored by changing the coefficient for the reactant O₂ to 8.

C₅H₁₂ + 8O₂ = 5CO₂ + 6H₂O

The numbers of C, H and O atoms on either side of the equation are now equal, and so the equation is balanced.

The balanced chemical equation (2): C₅H₁₂ + 8O₂ = 5CO₂ + 6H₂O

(3)

First, write the unbalanced equation: C₄H₆O₃ + H₂O = C₂H₄O₂ (unbalanced)

Next, count the number of each type of atom present in the unbalanced equation.

To balance the number of carbon atoms, a reasonable first attempt would be to change the coefficients for the C₄H₆O₃ and C₂H₄O₂ to integers that will yield 4 C atoms (the least common multiple for the C atom subscripts in these two formulas).

C₄H₆O₃ + H₂O = 2C₂H₄O₂

The numbers of C, H and O atoms on either side of the equation are now equal, and so the equation is balanced.

The balanced chemical equation (3): C₄H₆O₃ + H₂O = 2C₂H₄O₂