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Redox Reactions

Question
CBSEENCH11006786

In Ostwald’s process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.0 g of ammonia and 20.0 g of oxygen? 

Solution
Mass of the ammonia = 17 g
Mass of Oxygen molecule= 32g
Mass of nitric oxide= 30g
Mass of water =18g
The reaction involved in the manufacturing process is:
4 NH subscript 3 left parenthesis straight g right parenthesis space space space plus space space space space 5 straight O subscript 2 left parenthesis straight g right parenthesis space space rightwards arrow space space space space 4 NO left parenthesis straight g right parenthesis space space plus space space 6 straight H subscript 2 straight O left parenthesis straight g right parenthesis space space
4 x 17 = 68 g    5 x 32 = 160 g     4 x 30 = 120 g
From the available data:
68g of NH3 will react with O2  = 160 g
10g of NH3 will react with O210 space straight g space of space NH subscript 3 space will space react space with space straight O subscript 2 space equals space fraction numerator left parenthesis 160 space straight g right parenthesis over denominator left parenthesis 68 space straight g right parenthesis end fraction space cross times space left parenthesis 10 space straight g right parenthesis space equals space 23.6 space straight g
But oxygen which is actually available (20.0 g) is less than the amount which is needed. Therefore, oxygen is the limiting reactant. 
Now, 160 g of O2 will form NO = 120 g
therefore space 20 space straight g space of space straight O subscript 2 space will space form space NO space equals space fraction numerator left parenthesis 120 space straight g right parenthesis over denominator left parenthesis 106 space straight g right parenthesis end fraction cross times space left parenthesis 20 space straight g right parenthesis
space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 15 space straight g