A 1.800 g sample of octane, C8H18 was burned in a bomb calorimeter whose total heat capacity is 11.66 kJ/degrees C. The temperature of the calorimeter plus contents increased from 20.21 degrees C to 28.25 degrees C.
What is the heat of combustion per mole of octane?
delta H combustion = ???? kJ/mol
This is what I did and it was wrong:
q= C m delta T
so.... 11.66 kJ/C (1.8 g) 8.04 degrees C
= 168.7 k
168.kJ 114.22858 g (molecular wgt.)
---------- x ------------------------------------ = 10705.75
1.8 g 1 mol C8H18
That was the wrong answer....
So I don't know how to do the problem..
2007-03-13 21:57:26 · 2 answers · asked by piccolo504 2 in Science & Mathematics ➔ Chemistry
i divided by 1.8 and then multiply its molecular wgt.
2007-03-13 22:47:34 · update #1
look at that step as dimensional analysis...
answer molecular wgt.
--------- x ----------------------
1.8 g C8H18 moles of ChH18
2007-03-13 22:49:17 · update #2
answer ][ molecular wgt.
--------- x ----------------
1.8 ][ moles of compound
2007-03-13 22:50:53 · update #3
Zor Prime,
Where did you get the 3 from to multiply to the 11.66kj?? what happen to the mass in the equation:
q = C m delta T
2007-03-13 23:42:53 · update #4
you are multiplying by the 1.8 and then just dividing it out in the second step?
2007-03-13 22:04:43 · answer #1 · answered by tom t 2 · 0⤊ 0⤋
Lancenigo di Villorba (TV), Italy
CALCULATION
The bomb-calorimeter is a device is accompanied by a warrant about its Heat Capacity's value : the manifacturer measured it and affirm this value as a constant.
In this manner you calculate the heat evolved by the burning experiment
Q = C * DeltaT = 11.66E+3 * (28.25 - 20.21) = 93,746 J
This energy derived by a precise amount of OCTANE, that is
1.80 g as matter as (1.80 / 114) mol = 1.73E-2 mol
Thus, 1 mol of octane may evolve an heat's amount like
93,746 / 1.73E-2 = 5,937,247 J / mol
I hope this helps you.
2007-03-14 06:10:17 · answer #2 · answered by Zor Prime 7 · 0⤊ 0⤋