Is the following equation balanced: NH2CH2COOH (s) + 9/4 O2 --> 2 CO2 (s) + 5/2 H2O (l) + 1/2 N2 (g)?

1 Answer
Nov 2, 2015

No, balanced equation should be

2NH_2CH_2COOH + 9/2O_2 rarr 4CO_2 + 5H_2O + N_2

Explanation:

Let's write first the 'original' equation:

NH_2CH_2COOH + O_2 rarr CO_2 + H_2O + N_2 (unbalanced)

Let's begin tallying the atoms based on their respective subscripts

left side:

N = 1
H = 5
C = 2
O = 2 + 2 (do not add this up yet)

right side:

N = 2
H = 2
C = 1
O = 2 + 1 (do not add this up yet)

Since you have a rather large molecule on the left and simple molecules on the right, you have to choose one of those simple molecules to start balancing.

I'll start with H_2O. Since this is a substance, no matter what coefficient you multiply to H atom, you also have to apply to its bonded O atom.

NH_2CH_2COOH + O_2 rarr CO_2 + color (red) 5H_2O + N_2

left side:

N = 1
H = 5
C = 2
O = 2 + 2

right side:

N = 2
H = 2 x color (red) 5 = 10
C = 1
O = 2 + (1 x color (red) 5)

Notice that you now have 10 H atoms on your right, so you need to also have 10 H atoms on the left.

color (green) 2NH_2CH_2COOH + O_2 rarr CO_2 + 5H_2O + N_2

left side:

N = 1 x color (green) 2 = 2
H = 5 x color (green) 2 = 10
C = 2 x color (green) 2 = 4
O = (2 x color (green) 2) + 2

right side:

N = 2
H = 2 x 5 = 10
C = 1
O = 2 + (1 x 5)

Again, since your H atom is bonded to the N, C and O atoms, you also need to multiply the coefficient to them. Now let's balance the C atom.

2NH_2CH_2COOH + O_2 rarr color (blue) 4CO_2 + 5H_2O + N_2

left side:

N = 1 x 2 = 2
H = 5 x 2 = 10
C = 2 x 2 = 4
O = (2 x 2) + 2

right side:

N = 2
H = 2 x 5 = 10
C = 1 x color (blue) 4 = 4
O = (2 x color (blue) 4) + (1 x 5) = 13

Now the only atom left to balance is the O atom. Since the total number of O atoms on the right side is an odd number, I can use my knowledge on fractions to balance the equation.

2NH_2CH_2COOH + color (magenta) (9/2)O_2 rarr color (blue) 4CO_2 + 5H_2O + N_2

left side:

N = 1 x 2 = 2
H = 5 x 2 = 10
C = 2 x 2 = 4
O = (2 x 2) + (2 x color (magenta) (9/2)) = 13

right side:

N = 2
H = 2 x 5 = 10
C = 1 x 4 = 4
O = (2 x 4) + (1 x 5) = 13

The equation is now balanced.