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Chemistry question: equation products given reagents

Posted: Fri Jul 22, 2016 1:20 pm UTC
by sevenperforce
I can balance equations but only if I already know both sides. Trying to find the following products:

Na2S2O5 + O2 = ?

Na2S2O5 + KNO3 = ?

Na2S2O5 + KNO3 + Fe2O3 = ?

Na2S2O5 + KNO3 + C12H22O11 = ?

KNO3 + C12H22O11 = ?

KNO3 + C12H22O11 + Fe2O3 = ?

Thanks!

Re: Chemistry question: equation products given reagents

Posted: Fri Jul 22, 2016 1:49 pm UTC
by Soupspoon
sevenperforce wrote:I can balance equations but only if I already know both sides. Trying to find the following products:

It's been a while since I have done chemistry at such exam/test-level, but I presume you're expected that in...
Na2S2O5 + O2 = ?
...you're supposed to assume full combustion.

Thus (correcting some of the notation) Na2S2O5 + O2 → Na2O + SO2

But then you need to put the 'big' numbers in to balance it, which it sounds like you can do.

The other ones aren't obvious combustions (without checking ion affinities), but look to be suitable sources for ion-group swapping, reductions, etc. I'm almost certain that this is the kind of thing you get given as homework after being specifically told "a disulphite compound will typically react with these varieties of compounds to create such'n'such other type of compound", which should be all the clue you need to run with the rest.

But I await a chem-nerd telling me off for assuming that the first is a disintegrating oxidation, even, rather than prefering to become an even more richly oxygenated metasulphide/ite/whatever, or something else I haven't thought of yet.

Re: Chemistry question: equation products given reagents

Posted: Fri Jul 22, 2016 2:06 pm UTC
by sevenperforce
Soupspoon wrote:
sevenperforce wrote:I can balance equations but only if I already know both sides. Trying to find the following products:

It's been a while since I have done chemistry at such exam/test-level, but I presume you're expected that in...
Na2S2O5 + O2 = ?
...you're supposed to assume full combustion.

Thus (correcting some of the notation) Na2S2O5 + O2 → Na2O + SO2

But then you need to put the 'big' numbers in to balance it, which it sounds like you can do.

The other ones aren't obvious combustions (without checking ion affinities), but look to be suitable sources for ion-group swapping, reductions, etc. I'm almost certain that this is the kind of thing you get given as homework after being specifically told "a disulphite compound will typically react with these varieties of compounds to create such'n'such other type of compound", which should be all the clue you need to run with the rest.

But I await a chem-nerd telling me off for assuming that the first is a disintegrating oxidation, even, rather than prefering to become an even more richly oxygenated metasulphide/ite/whatever, or something else I haven't thought of yet.

They should all be reduction reactions. I'm sure this looks like a homework problem but I'm actually trying to find specific energies of different solid rocket propellants so this is just the very first step of several.

With KNO3 + C12H22O11 I know you get CO2 + H2O but I don't know where the nitrogen and potassium run off to.

Re: Chemistry question: equation products given reagents

Posted: Fri Jul 22, 2016 4:20 pm UTC
by pogrmman
sevenperforce wrote:
Soupspoon wrote:
sevenperforce wrote:I can balance equations but only if I already know both sides. Trying to find the following products:

It's been a while since I have done chemistry at such exam/test-level, but I presume you're expected that in...
Na2S2O5 + O2 = ?
...you're supposed to assume full combustion.

Thus (correcting some of the notation) Na2S2O5 + O2 → Na2O + SO2

But then you need to put the 'big' numbers in to balance it, which it sounds like you can do.

The other ones aren't obvious combustions (without checking ion affinities), but look to be suitable sources for ion-group swapping, reductions, etc. I'm almost certain that this is the kind of thing you get given as homework after being specifically told "a disulphite compound will typically react with these varieties of compounds to create such'n'such other type of compound", which should be all the clue you need to run with the rest.

But I await a chem-nerd telling me off for assuming that the first is a disintegrating oxidation, even, rather than prefering to become an even more richly oxygenated metasulphide/ite/whatever, or something else I haven't thought of yet.

They should all be reduction reactions. I'm sure this looks like a homework problem but I'm actually trying to find specific energies of different solid rocket propellants so this is just the very first step of several.

With KNO3 + C12H22O11 I know you get CO2 + H2O but I don't know where the nitrogen and potassium run off to.


KNO3 and sucrose isn't just a simple combustion. The products likely are a mix of K2CO3, K2O, various nitrogen oxides, CO2, H2O, and other things. Presumably the first step is nitrate giving up one oxygen to produce CO2, H2O, and NO2. The NO2 probably acts further as an oxidant. Without drawing it out and looking at it for a while, I'm not sure exactly what's formed.