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alphabeta
 one year ago
I am asked to calculate the enthalpy change for the combustion of 1 mole of sucrose. What I know from before is this;
Mass of sample of sucrose, m = 0.4385 g
Heat capacity of the system, c = 10.114 kJ K^1
I have also already calculated the amount of sucrose in moles to be 1.281*10^3 mol (and I know from the mark scheme that this is correct).
So, how to calculate the enthalpy change of combustion of one mole of sucrose?
alphabeta
 one year ago
I am asked to calculate the enthalpy change for the combustion of 1 mole of sucrose. What I know from before is this; Mass of sample of sucrose, m = 0.4385 g Heat capacity of the system, c = 10.114 kJ K^1 I have also already calculated the amount of sucrose in moles to be 1.281*10^3 mol (and I know from the mark scheme that this is correct). So, how to calculate the enthalpy change of combustion of one mole of sucrose?

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alphabeta
 one year ago
Best ResponseYou've already chosen the best response.0Another thing; I thought I could use this formula; Delta(H) = mass * capacity * delta(temperature), and then divide this by the number of moles (1.281*10^3). However, the mark scheme doesn't include the mass in its calculations. Why?

Zale101
 one year ago
Best ResponseYou've already chosen the best response.1\(−q=\Delta H∗n\) < this is the enthalpy change of burned sucrose, hence the negative q. n is the moles of sucrose (you were given the mass of sucrose, now you can easily calculate the mols by molar mass to mols conversion factor) But, we are solving for the enthalpy change ΔH. \(\Delta H=\Large\frac{−q}{n}\) We know that \(q=m∗c∗\Delta H\). So, we plug what equals to q into the enthalpy change formula \(ΔH=\large \frac{−(m∗c∗\Delta T)}{n}\)

alphabeta
 one year ago
Best ResponseYou've already chosen the best response.0Thank you for your response Zale101! However, the mark scheme says that I should do it this way to calculate the enthalpy change of combustion; ΔHc = (c*ΔT)/n When I first calculated it, I did it in the same way as you describe. However, for some reason, mass is not included in the formula (as the mark scheme says), and I don't understand why :o

cuanchi
 one year ago
Best ResponseYou've already chosen the best response.1In this case you have already the ΔH of a certain amount of glucose. It is correct calculate the moles in that grams. then is a simple conversion 1 mol of glucose x ( 10.114 kJ K^1/1.281*10^3 mol of glucose) = ????

Photon336
 one year ago
Best ResponseYou've already chosen the best response.0Q = mc(delta t) Delta H = q * n So mass would be in your formula if you substitute mCDelta T into q you get Delta H = (m*C*delta T)/(n)

alphabeta
 one year ago
Best ResponseYou've already chosen the best response.0As mentioned before, I have already used the formula "DeltaH = m*c*deltaT" and then divided it by the number of moles, but this doesn't give the correct answer, and I struggle to understand why :/ (Btw, deltaT = 0.67) The answer should be 5.3*10^3 kJ mol^1

cuanchi
 one year ago
Best ResponseYou've already chosen the best response.1That is the wrong formula to use to solve that problem!!!!

cuanchi
 one year ago
Best ResponseYou've already chosen the best response.1In this case you have already the ΔH of a certain amount of sucrose. you already correctly calculate the moles in that grams. then is a simple conversion 1 mol of sucrose x ( 10.114 kJ K^1/1.281*10^3 mol of sucrose) = ????
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