CHM
2045C Module Seven Sample Exam
Module
Seven Part C: Specific Heat/First Law Problems 10 points
If the temperature
of a 50.0 gram block of aluminum increases by 10.9 K when heated by 500 joules,
calculate
the: (See section
6.2 pages 241-246)
q = heat transferred C = specific heat capacity
m =
mass of substance
ΔT = change in K temperature
Heat capacity of Block = q / Δ T
Heat Capacity of Block = 500 J / 10.9
K = 45.9 J/K
Moles = 50.0 g / 27.0 g/mol =
1.85 mol
Molar heat capacity = q / Δ T mol
Molar Heat Capacity = 500 J / 10.9 K 1.85
mol = 24.8 J/K mol
q = C x m x Δ T
500 J = C x 50.0 g x 10.9 K C = 0.917 J/gK
If the internal energy of a thermodynamic
system is decreased by 300 J when 75 J of work is
done on the system, how much heat was transferred, and in which direction, to
or from the system. See section 6.4 p
253
Change Sign Conversion Effect of Esystem
Work
done on the system by surroundings w > 0 (+) E increases
Work
done by the system on surroundings w < 0 (-) E decreases
Heat
transferred to system from surroundings q > 0 (+) E increases
Heat
transferred from system to surroundings q < 0 (-) E decreases
Δ E = q +
w
Given Δ E= - 300 J w = + 75 J
- 300J = q + (+75J)
q = - 375 J of heat was
transferred from the system to the surroundings