IIT JEE , AIEEE Forum - Chemistry , Physical Chemistry

sucess_seeker

The reaction 2C + O₂

2CO is carried out by taking 24 g of carbon and 96 kg O₂

_{mole before reaction}24/12 96/32 0

mole after reaction 0 2 2 mole ratio 2:1:2

a) which reactant is left in excess

i cannot understand why we divide 24/12 etc and why 0, 2,2 and what significance mole ratio holds

raman_shadow

dude first of all u have mentioned amount of O₂ as 96 Kg
I think it shud be 96g. Otherwise it will clearly b in excess!!!

as u know atomic mass of carbon is 12 hence its gram atomic wt. is 12g
so moles of C will be (mass given/gram atomic wt.)
so moles of C r 24/12 = 2

also mass of O₂ given is 96g and its molecular wt. is 32 (remember O₂ is a molecule and not atom so the total wt. of molecule will be taken into concideration)
so moles of O₂ = 96/32 = 3
and if mass given is 96 Kg then its moles will be 96000/32

in the reaction by seeing the stoichiometric coefficients we can determine that
2 moles of C react with 1 mole of O₂ giving 2 moles of CO₂
as 2 moles of C r given and three of O₂ so after reaction with 2 moles of C reaction will stop leaving 2 moles of O₂ and 2 of CO₂. thats why it is 0,2,2
and O₂ is still left so it is in excess and C is called limiting reactant.

as minimum moles required for complete reaction r 2 for C and 1 for O₂ producing 2 CO₂ so is the ratio 2:1:2

pls rate me if u understood

sucess_seeker

as 2 moles of C r given and three of O₂ so after reaction with 2 moles of C reaction will stop leaving 2 moles of O₂ and 2 of CO₂. thats why it is 0,2,2
i could not understand this line a bit. You say 2 moles of carbon react leaving 0 mole, which means it is fully used and out of 3 moles 1 moles completely react to give 2 mole oxygen. why have u written reaction with carbon not with oxygen. how to know carbon will be utilised fully.

arun-rashi

the reaction is 2c +o2 gives CO in this reaction you know 2 moles of C while 3 moles of O2 are taken ,also 2x of carbon are utilised while x of o2 so 2x =2 ,x=1 we can say that carbon is limiting reagent according to mole eq always remember that in mole eq balancing is must,reactant also cunsumed in mole ratio.oxygen left in reaction is 1 mole while 2 mole of CO formation takes place.if this question solved by conservation of millieq method then this is already balanced by fector method.for ex 5 milieq of C reacts with 2 milieq of o2 so lf is o2 so 2 milieq of CO are formed and we easily determine unknown.

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