Balancing Reaction Pt 2

Question

Balance the following equations, if no coefficient is needed enter the number 1:

___H₃PO₄ + ___(NH₄)₂MoO₄ + ___HNO₃  ---> ___(NH₄)₃PO₄ x 12MoO₃ + __NH₄NO₃ + ___H₂O

Answer 1

Great example of a balancing equation that requires us to break down each element individually.

Let's start with our equation.

___H3PO4 + ___(NH4)2MoO4 + ___HNO3  ---> ___(NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

So we're going to separate the left side first. Our goal is to separate all the molecules into the individual elements -- then count the number of each element.

___H3PO4 + ___(NH4)2MoO4 + ___HNO3  --->

H - 3 + 1 = 4

(PO4) - 1

(NH4) - 2

Mo - 1

O - 4

(NO3) - 1

Notice that all molecules are in parentheses. We need to match each to the same molecule on the right side. If the molecules are not the same on each side, the elements need to be separated. For example, NO3 was able to stay intact because it is on both the left and right side of the equation. Conversely, MoO3 on the left becomes MoO4 on the right. So we need to separate Mo and Oxygen.

Now, let's do the separation and counting technique on the right side.

 ---> ___(NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

(NH4) - 3 + 1 = 4

PO4 - 1

Mo - 12

O - 3

(NO3) - 1

H - 2

O - 1

So now, we compare coefficients. We can start with ammonium, NH4. There's 2 on the left side of the equation, and 4 on the right side. So to make those numbers match, we multiply the left side of the equation by two.

___H3PO4 + 2 (NH4)2MoO4 + ___HNO3  ---> ___(NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

Now let's check in on our coefficients. We now have 2 Mo atoms on the left, but there's 12 on the right. To make THOSE numbers match, we must multiply the left coefficient by 6 to get 12.

___H3PO4 + 12 (NH4)2MoO4 + ___HNO3  ---> ___(NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

We now have 24 NH4 molecules on the left, and just 3 on the right. To make these numbers match, we'll multiply the right by 8.

___H3PO4 + 12 (NH4)2MoO4 + ___HNO3  ---> 8 (NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

Now our ammonium ion coefficients are adding up to match on both sides. We have 24 on the left and 24 on the right. Let's look at the phosphate ion, PO4. The left side of the equation has 1 phosphate molecule, and the right side has 8 phosphate molecules. So let's put an 8 in front of the left phosphate!

8 H3PO4 + 12 (NH4)2MoO4 + ___HNO3  ---> 8 (NH4)3PO4 + 12MoO3 + __NH4NO3 + ___H2O

Now let's count up our molecules on both sides again. After counting, if a number doesn't match, add a coefficient.

You should end up with the balanced equation below.

8 H3PO4 + 24 (NH4)2MoO4 + 24 HNO3  ---> 8 (NH4)3PO4 + 24 MoO3 + 24 NH4NO3 + 24 H2O

Count the molecules on each side to be sure they match.

left

H - 48

PO4 - 8

NH4 - 48

Mo - 24

O - 96

NO3 - 24

right

NH4 - 48

PO4 - 8

Mo - 24

O - 72 + 24 = 96

NO3 - 24

H - 48

Great! Everything matches. But notice, every coefficient in our balanced equation is divisible by 8. So let's go ahead and divide all coefficients by 8 and see what we end up with.

H3PO4 + 3 (NH4)2MoO4 + 3 HNO3  ---> (NH4)3PO4 + 3 MoO3 + 3 NH4NO3 + 3 H2O

Now, you just have to double check that the molecule count matches on both sides, and you're done! Great work!