science problems (balance equations)?

Question

i dont understand how
2SO2 + O2 ---> 2SO3
Wouldnt it be 4 if you were to add the o's?

or this

PCl + Cl2 = PCl5

how does this work??

Answer 1

For the first equation, I think you are confusing the sulfate ion (SO4-2) with sulfur trioxide. Two sufur dioxides, SO2, under the proper conditions, reacts with oxygen, O2, to produce sulfur trioxide SO3. Each SO2 takes one oxygen; the sufur goes from the +4 oxidation state to +6 and there is no charge because it is neutral compound, not an ion.

For the other one, I think there might be a typo, the starting material is probably PCl3 and converting to PCl5. It is phosporous in the +3 state going to the +5 state with the addition of 2 more chlorines.

Answer 2

Okay, the first equation has 2 Ss on the left and 2 Ss on the right. It has 2*2=4 +2 =6 oxygens on the left and 2*3=6 oxygens on the right, so it is balanced.

The second one balanced would be

PCl+2Cl2=PCl5

Now both sides had 1 P and 5 Cl....you just look at it and play around until things match up. You can search my answers and I explain it algebraically a few times.

Answer 3

Okay, the first equation has 2 Ss on the left and 2 Ss on the right. It has 2*2=4 +2 =6 oxygens on the left and 2*3=6 oxygens on the right, so it is balanced.

The second one balanced would be

PCl+2Cl2=PCl5

Now both sides had 1 P and 5 Cl....you just look at it and play around until things match up. You can search my answers and I explain it algebraically a few times.