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A Level Chemistry Question

Hi I was just wondering if someone could help me out with this moles question:

When heated copper oxide reacts with gaseous ammonia to form copper;
2CuO(s) + 2NH3(g) → 2Cu(s) + N2(g) + 3H2O(g)
If the reaction takes place to completion using ammonia and an excess of copper oxide, which of the following will be found?
A) At 400 C, the volume of the products will be twice the volume of the
ammonia that was used
B) If the reaction is cooled to room temperature, the volume of the products will be half the volume of ammonia that was used
C) The amount in mol of copper obtained will be half the amount in mol of copper oxide that was used

I understand why A and C are incorrect but I just don't understand how you could work out B...

(edited 4 years ago)

Reply 1

charco

Study Forum Helper

Avogadro's law tells us that the volume of a gas is proportional to the moles.
The coefficients of the equation show the moles ratio of reactants and products
Both A and B are correct.

Reply 2

studyingpeach

Original post by charco

Avogadro's law tells us that the volume of a gas is proportional to the moles.
The coefficients of the equation show the moles ratio of reactants and products
Both A and B are correct.

According to the mark scheme A is incorrect. I thought this too because there would be 6 moles of products and 2 moles of ammonia - if the statement was correct there would be 4 moles of products so A should be incorrect.
But for B I don't understand how you could work out the gas volumes at a different temperature?

Reply 3

Ben878

Since the proportions of moles to volume are used (as charco said) the temp wouldn't make a difference. (You could assume it as 24 degrees, but ratio gives you an answer without knowing the temp)

(edited 4 years ago)

Reply 4

studyingpeach

Original post by Ben878

Since the proportions of moles to volume are used (as charco said) the temp wouldn't make a difference. (You could assume it as 24 degrees, but ratio gives you an answer without knowing the temp)