A lvl Chemistry MCQ

• Bigcable22

  15 Nov 08, 18:28

  found this puzzling question in my friends worksheet..  not in CxHy ..

  In an experiment 10cm^3 of organic compound X in the gaseous state was sparked in excess oxygen.20cm^3 of carbon dioxide and 5cm^3 of nitrogen were obtained among the products.All gas volumes were measured at the same temperature and pressure.

  which of the following compounds could be X?

  1.) C2H7N

  2.)C2H6N2

  3.)C6H5NO2

  4.)C3H5N

• arigatoast

  15 Nov 08, 23:19

  ans is 1) C2H7N

  ratio of X : CO2: N2

              2       4       1

  that means there are 4/2=2 carbon atoms  in X

  which also means there is 2/1= 1  N atom in X

  

   

• UltimaOnline

  15 Nov 08, 23:21

  Originally posted by Bigcable22:

  found this puzzling question in my friends worksheet..  not in CxHy ..

  In an experiment 10cm^3 of organic compound X in the gaseous state was sparked in excess oxygen.20cm^3 of carbon dioxide and 5cm^3 of nitrogen were obtained among the products.All gas volumes were measured at the same temperature and pressure.

  which of the following compounds could be X?

  1.) C2H7N

  2.)C2H6N2

  3.)C6H5NO2

  4.)C3H5N

   

  This question is in error. In every one of the 4 options, combustion in excess oxygen would definitely produce several species of oxides of nitrogen (NxOy), and not nitrogen gas.

  If ignoring this critical error AND assuming the only product of combustion containing nitrogen is N2 gas, then the answer would be option 1, since by stoichiometry, combustion of 10cm3 of the compound produces 20cm3 CO2 implies 2 C present, and 5cm3 N2 produced implies 1 N present. The hydrogens in the compound would simply be oxidized to water. 

• UltimaOnline

  15 Nov 08, 23:28

  Originally posted by arigatoast:

  ans is 1) C2H7N

  ratio of X : CO2: N2

              2       4       1

  that means there are 4/2=2 carbon atoms  in X

  which also means there is 2/1= 1  N atom in X

  

   

  
  Ah, I see arigatoast hit the "post" button before me. He's quick on the draw. Fast and reliable service, with a "" (smile) too.