Stoichiometry of NaNO3
Billybobjoe, Sun Jan 21 2007, 09:34PMI've found a local, fairly cheap source for sodium nitrate and I've tried it in a few compositions with sugar, and the bright orange sodium flame makes for a nice flare. I've haven't been able to perfect the mixture because I don't know what the stoimetric mix is. For KNO3 and sucrose, (candy rocket mixture) its 66/34 (or sometimes 65/35 for better casting and whatnot).
Something tells me that it should be relatively easy to determine using NaNO3 instead of KNO3 using the difference in atomic masses, but I'm not there yet in chemistry. Anyone know? Thanks!
Re: Stoichiometry of NaNO3
Chris, Sun Jan 21 2007, 10:28PM
Sucrose is C12H22O11, and a combustion reaction with sodium nitrate would likely yield Na2O + N2 + CO2 + H2O. Balancing this equation (and no, I didn't do it in my head, there are online calculators that can do it for you), you get 5C12H22O11 + 48NaNO3 -> 24Na2O + 24N2 + 60CO2 + 55H2O. Other oxidation states are possible (and even more likely given the conditions) as well with these reactions, yielding K2O2, KO2, or their sodium analogs. With the superoxide, the equation looks like C12H22O11 + 24NaNO3 -> 24NaO2 + 12N2 + 12CO2 + 11H2O, resulting in a vastly different stochiometry. With the peroxide, we get C12H22O11 + 12NaNO3 -> 6Na2O2 + 6N2 + 12CO2 + 11H2O. As far as I know, potassium has more of a tendency to form peroxide and superoxide than sodium.
Sucrose has an atomic mass of 342.3g/mol, KNO3 has a mass of 101.1, and NaNO3 is 85.0. This means the stochiometric mix of sucrose to KNO3 resulting in potassium peroxide (K2O2) will be 3.5:1 by weight, and you should be able to figure out the other stochiometric ratios with this information. In rocket compositions in practice, excess fuel is often used in the mixture. Also it may be difficult to predict the exact composition of the oxides formed by the reaction, which vastly affect stochiometry as you can see. This is why I don't like metal based oxidizers. They are confusing (they also produce a high mass exhaust which is detrimental from a performance standpoint, though sodium nitrate should outperform potassium nitrate in this respect). You will probably need to do extensive experimentation to determine the true ideal mix unless you can find it through some other source. A good place to start might be simply subtracting the mass difference per mole between sodium and potassium nitrates for your mix, based on the information out there on potassium nitrate compositions.
Chris, Sun Jan 21 2007, 10:28PM
Sucrose is C12H22O11, and a combustion reaction with sodium nitrate would likely yield Na2O + N2 + CO2 + H2O. Balancing this equation (and no, I didn't do it in my head, there are online calculators that can do it for you), you get 5C12H22O11 + 48NaNO3 -> 24Na2O + 24N2 + 60CO2 + 55H2O. Other oxidation states are possible (and even more likely given the conditions) as well with these reactions, yielding K2O2, KO2, or their sodium analogs. With the superoxide, the equation looks like C12H22O11 + 24NaNO3 -> 24NaO2 + 12N2 + 12CO2 + 11H2O, resulting in a vastly different stochiometry. With the peroxide, we get C12H22O11 + 12NaNO3 -> 6Na2O2 + 6N2 + 12CO2 + 11H2O. As far as I know, potassium has more of a tendency to form peroxide and superoxide than sodium.
Sucrose has an atomic mass of 342.3g/mol, KNO3 has a mass of 101.1, and NaNO3 is 85.0. This means the stochiometric mix of sucrose to KNO3 resulting in potassium peroxide (K2O2) will be 3.5:1 by weight, and you should be able to figure out the other stochiometric ratios with this information. In rocket compositions in practice, excess fuel is often used in the mixture. Also it may be difficult to predict the exact composition of the oxides formed by the reaction, which vastly affect stochiometry as you can see. This is why I don't like metal based oxidizers. They are confusing (they also produce a high mass exhaust which is detrimental from a performance standpoint, though sodium nitrate should outperform potassium nitrate in this respect). You will probably need to do extensive experimentation to determine the true ideal mix unless you can find it through some other source. A good place to start might be simply subtracting the mass difference per mole between sodium and potassium nitrates for your mix, based on the information out there on potassium nitrate compositions.
Re: Stoichiometry of NaNO3
..., Sun Jan 21 2007, 10:38PM
Doh! chris beat me to it
The change from Na to K is easy, just convert from mass NaNO3 to mass C12H22O11 (using the normal 5C12H22O11 + 48KNO3 -> 36CO2(g) + 55H2O(g) + 24N2(g) + 24K2CO3) and then divide
ie
Start with 1g NaNO3 * (1mol NaNO3 / 88.995g NaNO3) * (5mol C12H22O11 / 48mol NaNO3) * (342.300g C12H22O11 / 1mol C12H22O11) which equals 1.551g C12H22O11. So if you want the ratio sugar/nitrate just divide (1.551g C12H22O11) / ( 1g NaNO3 + 1.55g C12H22O11) which gives a 60.7/39.3 ratio.
But, the reaction will be different for Na, and you don't actually want a stoichiometric ration, so really, just test it and see what works best
BTW, if you don't like adding the masses the of the elements, there are a lot of calculators to do it for you
(a few of my favorites)
..., Sun Jan 21 2007, 10:38PM
Doh! chris beat me to it
The change from Na to K is easy, just convert from mass NaNO3 to mass C12H22O11 (using the normal 5C12H22O11 + 48KNO3 -> 36CO2(g) + 55H2O(g) + 24N2(g) + 24K2CO3) and then divide
ie
Start with 1g NaNO3 * (1mol NaNO3 / 88.995g NaNO3) * (5mol C12H22O11 / 48mol NaNO3) * (342.300g C12H22O11 / 1mol C12H22O11) which equals 1.551g C12H22O11. So if you want the ratio sugar/nitrate just divide (1.551g C12H22O11) / ( 1g NaNO3 + 1.55g C12H22O11) which gives a 60.7/39.3 ratio.
But, the reaction will be different for Na, and you don't actually want a stoichiometric ration, so really, just test it and see what works best
BTW, if you don't like adding the masses the of the elements, there are a lot of calculators to do it for you
(a few of my favorites)Re: Stoichiometry of NaNO3
Billybobjoe, Sun Jan 21 2007, 11:27PM
Thanks guys. ... - I"ll give that ratio a try - at least that narrows it down somewhat so the range of experimenting is much lower. Also, this isn't necessarily for a rocket propellent, I just want a stable burn without to much extra molten NaNO3 and sugar spurting out. This is sort of a flare/fire starter kind of thing.
Should I even ask how one would substitute NaNO3 in black powder?
Billybobjoe, Sun Jan 21 2007, 11:27PM
Thanks guys. ... - I"ll give that ratio a try - at least that narrows it down somewhat so the range of experimenting is much lower. Also, this isn't necessarily for a rocket propellent, I just want a stable burn without to much extra molten NaNO3 and sugar spurting out. This is sort of a flare/fire starter kind of thing.
Should I even ask how one would substitute NaNO3 in black powder?
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