**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:** (

*heat*.*capacity of the aluminum block*

**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**

*molar*.*heat capacity of aluminum***Moles = Mass / Molar Mass**

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**

*specific*.*heat capacity of aluminum*

**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 E _{system}**

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**