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September 3, 2015

Homework Help: Chem

Posted by Shawn on Friday, February 2, 2007 at 10:25pm.

Nitric acid is produced commercially by the Ostwald
process, represented by the following equations:
4NH3(g) + 5O2(g) > 4NO(g) + 6H2O(g)
2NO(g) + O2(g) > 2NO2 (g)
3NO2(g) + H2O(l) > 2HNO3(aq) + NO(g)
What mass of NH3 must be used to produce 1.0x10^6 kg HNO3 by the Ostwald
process? Assume 100% yield in each reaction [and assume that the NO produced in the third step is not recycled.]

--HNO3 mols =15873015.87
which means 95238095.24 mols of NO2
Because the coefficient of NO2 and NO and NO and NH4 are the same, there are 95238095.24 NH4.
Multiply that by the molar mass (17) and divide by 1000 gets me 1619047.619 kg. Is this right?

No, I don't think it is right.
mols HNO3 is correct EXCEPT that you don't have that many significant figures.
1.0E6 kg x (1000g/kg)= 1.0E9 g
1.0E9g x 1 mol HNO3/63 g = 1.587E7 (and that is too many places, also).
I THINK you used the wrong factor to convert to mols NO2. I THINK you used
1.587E7 x 2/3 but it should be 3/2; i.e.,
mols HNO3 x (3 mols NO2/2 mols HNO3) = mols NO2. You are correct that everyting else is 1:1 so mols NO2 will be same as mols NH3 and you convert that to g NH3 by multiplying the molar mass NH3 as you posted. Check my thinking.

Apparently i did use some wrong factor.
Is the answer 4.0 x 10^5 kg correct?

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