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What mass of oxygen is required to oxidise 10g of ammonia to NO? + another question.

Hi I'm having real trouble with a couple of questions can someone walk me through them step by step. I have another 14 or so to do but if I can see how to do these two it would help me understand.

What mass of oxygen is required to oxidise 10g of ammonia to NO?

4 NH3 + 5 O2 ---> 4 NO + 6 H2O


What mass of potassium oxide is formed when 7.8 g of potassium is burned in oxygen.

4 K + O2 ---> 2 K2o

Thanks in advance and please try to go through both of them because they are slightly different in set up.
Original post by Nitrogen09
Hi I'm having real trouble with a couple of questions can someone walk me through them step by step. I have another 14 or so to do but if I can see how to do these two it would help me understand.

What mass of oxygen is required to oxidise 10g of ammonia to NO?

4 NH3 + 5 O2 ---> 4 NO + 6 H2O


What mass of potassium oxide is formed when 7.8 g of potassium is burned in oxygen.

4 K + O2 ---> 2 K2o

Thanks in advance and please try to go through both of them because they are slightly different in set up.


My chemistry teacher taught us to remember the formula triangle 'Gee, Mr Mole' where 'g' goes on top of the triangle and 'Mr' and 'moles' are on the bottom. 'g' stands from grams (so weight), 'Mr' stands for relative molecular mass and 'moles' is obviously the number of moles.

The second question is the most straightforward so I will go through it first. The Mr of potassium is 39, so you do 7.8/39 = 0.2 so you have 0.2 moles of potassium. now in the chemical equation potassium has 4 moles and K2O has 2 so the ratio is 2:1 so you know you have 0.1 moles of K2O. you then just use the formula in reverse, molesxMr=0.1x(39+39+16)=9.4.

For the first question you just do 10/30=0.3. The ratio is 4:5 so its 0.3:0.42 (depends on how you round). Then you do 0.42x32=13.44.

Hope this helped. My chemistry teacher always used to say 'If in doubt, mole it!'
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Nitrogen09
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Hope this helped. My chemistry teacher always used to say 'If in doubt, mole it!'


Thank you so much! You are a real life saver.

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