Wednesday, November 24, 2010

I need help with my homework questions please?

How much heat energy is required to raise the temperature of 5 kilograms of coal from 20掳C to 220掳C?



A. 314 J

B. 6,573 J

C. 1,314,718 J

D. 4,187,000 J





10. One degree Celsius indicates the same temperature change as



A. one degree Fahrenheit.

B. one kelvin.

C. 5/9 degree Fahrenheit.

D. 9/5 kelvin.





11. A quantity of a gas has an absolute pressure of 400 kPa and an absolute temperature of 110 degrees kelvin. When the temperature of the gas is raised to 235 degrees kelvin, what is the new pressure of the gas? (Assume that there's no change in volume.)



A. 1.702 kPa

B. 3.636 kPa

C. 510 kPa

D. 854.46 kPaI need help with my homework questions please?
The first question is impossible to answer since we do not know the specific heat capacity of the coal, and that this will change with the composition of the coal, as brown coal, green coal or anthracite will have differents amount of carbon, hydrogen, nitrogen,sulphur, oxygen, and ash. This will vary from mine to mine.



Question 9 is B.



Question 10 P1V1/T1=P2V2/T2 but V1=V2 then



P1/T1= P2/T2



Therefore



P2= P1*T2/T1=400*235/110= 854.545kPa, Answer D.
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