[Invertalon]

These problems were given to us, due tommorrow as some mad bonus points for us, and I cannot figure them out, and need serious *delete me* It is greatly appreciated!

P2I4 + P4 + H2O -->  PH4I + H3PO4

and...

KClO3 + HCl -->  KCl + H20 + Cl2 + ClO2



Thank you all so very much... I need all the hllp I can!

[jdurg]

Show us how far you've gotten and we can help you get through the parts you're stuck on.  If we just did it for you, you'd never learn how to do it on your own.  So just post how far you've gotten and what part of the balancing is getting you stuck.  

[Invertalon]

I actually got the first one, which was worth more points...

My final answer for that was...

10 P2I4 + 13 P4 + 128 H2O --> 40 PH4I + 32 H3PO4




But the second one I am stuck on now.. (she said it had 2 possible answers)

KClO3 + HCl --> KCl + H2O + ClO2 + Cl2

My answer SO FAR is...

6KClO3 + 9HCl = 6KCl + 5H2O + 7ClO2 + Cl2          

leaving...

K - 6                          K- 6
Cl- 15                       Cl- 15
O- 18                        O- 19
H- 9                          H- 10

I always seem to get a differance of one on both sides no matter how far I go

[jdurg]

Well, remember, you can always start out by balancing it with fractions as coefficients.  Then you can just use some simple mathematics to eliminate the fractions and get a whole number.  It's also important to try and see which is the 'key' compound in the reaction.  Every reaction has one compound which really controls the progress of the balancing.  In this case, it would be KClO3 since it contains K, Cl, and O in its formula.  It's only missing the H which is easy to balance since H is only present in the water on the right side.  So you'd start out by eliminating pretty much everything but the KClO3.  So I would start like this:

KClO3 -> ClO2 + KCl

With this step the potassium is balanced, but the chlorine is one too many on the right and the oxygen is one two few.  So to correct this we will bring in the HCl portion and the water.  This gives:

KClO3 + HCl -> KCl + H2O + ClO2

Now the potassium is balanced, the oxygen is balanced, and the chlorine is balanced.  But the hydrogen is short one on the left side.  So we'll add another molecule of HCl to give us:

KClO3 + 2HCl -> KCl + H2O + ClO2

Now the potassium is balanced, the hydrogen is balanced, and the oxygen is balanced.  Sadly, the chlorine is off with 3 on the left side and only two on the right.  So now we'll bring in our final part of this equation which is the chlorine gas.  This can be balanced by using a 1/2 coefficient which gives us:

KClO3 + 2HCl -> KCl + H2O + ClO2 + (1/2)Cl2

Now everything is balanced.  So we just need to multiply every coefficient by two to get a balanced, whole number coefficient for each substance.

2KClO3 + 4HCl --> 2KCl + 2H2O + 2ClO2 + Cl2

It is now balanced.  

[AWK]

The first redox is also quite easy. One can find that some P4 is needed for producing PH4I
2P2I4+ P4 (=P8I8) => 8PH4I
Then in normal way one can find coefficients for reaction
P8I8 + P4 + H2O = PH4I + H3PO4
with coefficient 5+8+132=5+32
which are equivalent to
40+13+128=40+32 for original reaction

Printing error correction

[Invertalon]

Jdurg,

Thanks so much for the help. I never thought of using a 1/2 coef. and then just multiplying up. That will help alot with these harder ones, well, hard in my eyes.

Thank you again!

[jdurg]

Jdurg,

Thanks so much for the help. I never thought of using a 1/2 coef. and then just multiplying up. That will help alot with these harder ones, well, hard in my eyes.

Thank you again!

No problem.  I'm happy to see that you were able to work most of it out on your own and came up with solid solutions.  As I've always believed; it doesn't really matter how you get there just as long as you get there.  So if you have to use fractional coefficients to get the solution, then that works out just fine.  It's just always important to figure out which compound is the key to the whole solution.  In the one I went through, it was pretty easy to see how closely related KClO3 and ClO2 were.  For some of the tougher reactions, there can be multiple 'key compounds' which can make things incredibly difficult.  Good luck!