K3PO4(aq) + 3Sr(NO3)2 ==> Sr3(PO4)2 + K2(NO3)

the reactant was given.
I can't seem to balance this.

whenever everything is even either the 3Sr(NO3)2 or K2(NO3) is not balanced.
Also, the 3Sr in 3Sr(NO3)2 was already there.

What should I do when the reactant seems to already be balanced or has a coefficent?

figured it out

I hope you figured out that the formula for potassium nitrate is KNO3 and not K2NO3.

Balancing chemical equations can be a bit tricky at times, but there is a systematic approach to solve it. Here's how you can balance the given equation step by step:

Step 1: Count the number of atoms on each side of the equation.

On the left side:
- K: 1
- P: 1
- O: 4
- Sr: 0
- N: 6

On the right side:
- K: 2
- P: 2
- O: 10
- Sr: 3
- N: 2

Step 2: Begin by balancing the elements that appear in the fewest compounds first. In this case, we can start by balancing potassium (K) and strontium (Sr).

To balance K, we need to have two K atoms on the left side. Multiply K3PO4 by 2, which gives us:
2K3PO4(aq) + 3Sr(NO3)2 -> Sr3(PO4)2 + K2(NO3)

Now, the number of K atoms on both sides is balanced.

Step 3: Next, we balance the strontium (Sr). We have 3 Sr atoms on the left side and only 1 on the right side.

To balance Sr, multiply Sr(NO3)2 by 3, which gives us:
2K3PO4(aq) + 9Sr(NO3)2 -> Sr3(PO4)2 + K2(NO3)

Now, the number of Sr atoms on both sides is balanced.

Step 4: Finally, balance the remaining atoms, which are phosphorus (P), nitrogen (N), and oxygen (O).

- P: We have 1 P atom on the left side and 2 on the right side. Multiply Sr3(PO4)2 by 2, which gives us:
2K3PO4(aq) + 9Sr(NO3)2 -> 2Sr3(PO4)2 + K2(NO3)

Now, the number of P atoms on both sides is balanced.

- N: We have 6 N atoms on the left side and 2 on the right side. Multiply K2(NO3) by 3, which gives us:
2K3PO4(aq) + 9Sr(NO3)2 -> 2Sr3(PO4)2 + 3K2(NO3)

Now, the number of N atoms on both sides is balanced.

- O: We have 4 O atoms on the left side and 10 on the right side. Multiply K2(NO3) by 5 and Sr(NO3)2 by 2, which gives us the final balanced equation:
2K3PO4(aq) + 6Sr(NO3)2 -> 2Sr3(PO4)2 + 3K2(NO3)

Now, the number of O atoms on both sides is balanced.

So, the balanced equation is:
2K3PO4(aq) + 6Sr(NO3)2 -> 2Sr3(PO4)2 + 3K2(NO3)