Gas Laws, STP, amount of products: Chem homework help?

Question

for the record, this is one of only a few homework problems of a whole assignment that i couldn't figure out, and no i did not put it off until the last minute...

When 35.6L of ammonia and 40.5L of oxygen gas at STP burn, nitrogen monoxide and water form.  After the products return to STP, how many grams of nitrogen monoxide are present?

unbalanced:  NH3(g) + O2(g) => NO(g) + H2O(l)

balanced:  4NH3 + 5O2 => 4NO + 6H2O

if you could please explain it and not just give an answer that would be great!

HPV · Accepted Answer

At STP, one mole of any gas has a volume of 22.4 L.

35.6 L NH3 x (1 mole NH3 / 22.4 L NH3) = 
1.59 moles NH3

40.5 L O2 x (1 mole O2 / 22.4 L O2) =
1.81 moles O2

Now the question is: Which one of the reactants (NH3 or O2) will be used up first?

According to the balanced equation above, it takes 5 moles of O2 to react with every 4 moles of NH3. 

1.59 moles NH3 x (5 moles O2 / 4 moles NH3) = 1.99 moles O2. But we have only 1.81 moles of O2, not enough to react with all the NH3. So O2 will be used up first. How much NO will it make? According to the balanced equation, 5 moles of O2 will produce 4 moles of NO.

1.81 moles O2 x (4 moles NO / 5 moles O2)
x (30.0 g NO / 1 mole NO) = 43.4 g NO

Erika · Answer

whats up so which you would be able to appreciate the lesson attempt to reply to it your self. prevalent Temperature and tension: Temp - 0(stages celsius) = 273 kelvin tension - 1atm i think of you will desire to get the molecular weight of Nitrogen. Its quite basic. attempt it!

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Gas Laws, STP, amount of products: Chem homework help?

2 Answers