January 23, 2017

Homework Help: Chem

Posted by Anonymous on Wednesday, March 27, 2013 at 6:31pm.

Calculate the work (in kJ) when 1.80 moles of methane react with excess oxygen at 389 K:

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

I got 11661.26

Calculate the change in entropy (in J/K) when 70.1 g of nitrogen gas is heated at a constant pressure of 1.50 atm from 12.0 ºC to 63.0 ºC. (The molar specific heats are Cv is 20.8 J/(mol-K) and Cp is 29.1 J/(mol-K) .)

I got 63.2

Using the technique of the previous problem ΔE was found to be -2,000.00 kJ/mol of an unknown liquid hydrocarbon at 298 K. In another experiment it was determined that for each mole of hydrocarbon, 4 moles of oxygen gas are consumed and 9 moles of CO2 gas and 4 moles of H2O liquid are produced. Find ΔH per mole of this hydrocarbon (in kJ) at 298 K.

I did something along these lines:
ΔH = ΔE+PΔV = ΔE + ΔnRT for gases.
A comment on the last 2 problems. Normally, ΔH is calculated, then ΔE because it is easier to do experiments at constant pressure.
And got 10381.9

None of these are right unfortunately so please help! Thanks!

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