2C2H6+702---->4CO2+6H20
DELTAH= -3120.6 kJ/mol
What mass of ethane must be combusted in order to heat 366 g of water from 25 degree celcius to 100 degree celcius? Assume the heat transfer is 100% efficient.
a)44.1 g
b) .903g
c) 3.61g
d) 2.21 g
Should I approach this problem by q=m*s*delta T??
I know the answer is d. I don't know how to approach the problem
Yes, that approach will get you there, at least that's a good place to start.
How much heat do you need to heed the water? That's
q = mass H2O x specific heat H2O x (Tfinal-Tinitial) = ?
Then 3120.6 kJ/mol x (grams ethanol/2*(molar mass C2H6) = q
Solve for grams ethanol and round to 3 significant figures.
I have got the answer but can you explain me which formula you used after calculating q in part 1?
The easy way is to say I used good old fashioned reasoning but that's not the kind of answer you're looking for.
I think q comes out to be approx 115 kJ; let's just say that that's the answer for q = mcdT.
Then here is what we have.
The molar mass of ethane (sorry--I wrote ethanol in the response--my bad) is 30 so 2*30 = 60 g ethane produced 3120.6 kJ. We want to know know how many g will produce 114.8 kJ. We set up a proportion like this
(60g/3120.6 kJ) = (x g/114.8) so
x = 60*114.8/3120 = 2.207 = 2.21 g.
Instead of setting up a proportion I cobbled together a linear expression that basically says
known kJ heat by ethane/g x grams = heat needed.
Hope this helps.
By the way, I think there is an error in the problem. When it says dH is -3120.6 kJ/mol they really mean -3120 kJ/rxn (thats for 2 mols). It 3120.6/2 kJ/mol.
To approach this problem, you need to use the equation q = m × s × ΔT, where q represents the heat transferred, m is the mass of the substance, s is the specific heat capacity, and ΔT is the change in temperature.
In this case, you want to heat 366 g of water from 25°C to 100°C. The specific heat capacity of water (s) is 4.18 J/g°C. However, you are given the reaction and enthalpy change for the combustion of ethane (2C2H6 + 7O2 → 4CO2 + 6H2O), not the specific heat capacity of the water.
To solve this problem, you can calculate the heat transferred during the combustion of ethane and then use that information to find the mass of ethane needed.
First, calculate the heat transferred during the combustion of ethane:
ΔH = -3120.6 kJ/mol
The molar mass of ethane (C2H6) is:
2(C) + 6(H) = 12.01 g/mol + 6(1.01 g/mol) = 30.07 g/mol
Using the balanced equation, you can see that for every 2 moles of C2H6 combusted, 6 moles of H2O are formed.
Now, convert the given mass of water to moles:
m(H2O) = 366 g
moles(H2O) = m(H2O) / molar mass(H2O)
= 366 g / (2(H) + 16(O))
= 366 g / (2(1.01 g/mol) + 16.00 g/mol)
≈ 20.32 mol
Since the stoichiometry of the reaction shows that 2 moles of C2H6 are required to produce 6 moles of H2O, you can set up a proportion to find the moles of C2H6:
moles(C2H6) / moles(H2O) = 2 / 6
moles(C2H6) = (2 / 6) × moles(H2O)
= (2 / 6) × 20.32 mol
≈ 6.77 mol
To find the mass of ethane needed, use the molar mass of ethane:
mass(C2H6) = moles(C2H6) × molar mass(C2H6)
= 6.77 mol × 30.07 g/mol
≈ 203.59 g
Therefore, the mass of ethane needed to heat 366 g of water from 25°C to 100°C is approximately 203.59 g. Since none of the given answer choices match, it seems there might be a mistake in the question or options.