Question

bio gas is a mixture of gases.according to its volume 85% C2H6, 6% CH4, 5% CO , 2% CO2 , 0.5% N2 and remaining is deactivated gas. Bio gas is burnt in a cylinder of 0.25m^3 volume. then the emitted heat is used to boil 100l of water in an aluminium vessel of 10kg.At the beginning temperature was 25C . At the end it was 100C in the vessel. 20% of the heat emitted was wasted.
S.H.C of water is 4200
S.H.C of Al is 2666.67


C2H6 + 7/2 O2 =====2CO2 + 3H2O -4500kJmol

CH4 + 2O2 ====CO2 + 2H2O -2000kJmol

CO + 1/2 O2 ==== CO2 -1500kJmol


1. Find the emitted heat,No. of moles

Answer 1

They gave you a lot of information thats not necessary to answer the question.

q=80% of heat emitted \(\dfrac{q}{0.8}=\dfrac{q_T}{1}\)

so \(q_T=\dfrac{q}{0.8}\)

\(q_T=\dfrac{q}{0.8}=\underbrace{m*C_P*\Delta T}_{water}+\underbrace{m*C_P*\Delta T}_{Al}\)

Answer 2

\(q_T=\dfrac{\underbrace{m*C_p*\Delta T}_{water}+\underbrace{m*C_p*\Delta T}_{Al}}{0.8}\)

that last equation should've read.

and they want the number of moles of what?

Answer 3

Actually I don't know what no. of moles they want?
It says Total moles
I think it's total moles in bio gas mixture

When calculating heat emitted why is it divided by 0.8? They ask total heat that emitted
though 20% is wasted it's also heat emitted right?
Please reply!

Answer 4

because we want to know 100% of the heat emitted, by dividing by 0.8 you find that. (look at the first ratio i posted).

hm it seems that you could just take the weighted average of the heat evolved, so:

q= [85%*(-4500 kJ/mol)+6%*(-2000 kJ/mol)+ 5%(-1500 kJ/mol)]*n

Answer 5

Finding the no. of moles is the problem for me

Answer 6

Also this is a part of a question the details given are needed for the other parts

Answer 7

unless the percentages are given in mass, which then you'd have to assume some mass to correct for that.

Answer 8

i thought of that but N2 too is burnt right? they have not given a reaction for that
but a certain amount of energy is emitted through it also right?

Answer 9

\(N_2\) will likely stay as \(N_2\)

Answer 10

it's very inert

Answer 11

in the next part they ask no of moles of CO,CO2,N2,CH4,C2H6 and deactivated gas separately in the cylinder.How do you find that?

Answer 12

i think you might need to do some more other stuff to account for moles, because whats given might be in mass.

Answer 13

i'm pretty sure that its given in volume
can't we say that volume is directly proportional to moles( Avogadro law)

Answer 14

OH it is definitely in volume. Then yes, proceed with:

q= [85%*(-4500 kJ/mol)+6%*(-2000 kJ/mol)+ 5%(-1500 kJ/mol)]*n

Answer 15

then you wanna do another ratio to find the total number of moles

n/96%=\(n_T\)/100%

Answer 16

I didn't understand it
I found the total no. of moles = 8.33 mol
to find moles of each gas can we multiply it by there volume percentages?

Answer 17

yes