Cliffs AP Chemistry, 3rd Edition

2. A piece of metal weighing 500. grams is put into a boiling water bath. After 10 minutes,
   the metal is immediately placed in 250. grams of water at 40.°C. The maximum
   temperature that the system reaches is 50.°C. What is the specific heat of the metal?

(The specific heat of water is 1.00 cal/g ⋅°C.)

A. 0.010 cal/g ⋅°C

B. 0.050 cal/g ⋅°C

C. 0.10 cal/g ⋅°C

D. 0.20 cal/g ⋅°C

E. 0.50 cal/g ⋅°C

Answer: C

Begin this problem by realizing that the heat gained by the water is equal to the heat lost by the
metal.

heat lost or gained = specific heat of the substance ×mass of the substance ×∆t

Substituting the numbers into this concept gives

heat gained by water = heat lost by metal

(1.00 cal/g ⋅°C) ×(250. g H 2 O) ×(50.°C −40.°C) =

−(xcal/g ⋅°C) ×(500. g metal)(50.°C −100.°C)

2500 = 25,000 x

x= 0.10 cal/g ⋅°C

3. Given the following heat of reaction and the bond energies listed in the accompanying
   table, calculate the energy of the C==O bond. All numerical values are in kilocalories
   per mole, and all substances are in the gas phase.

CH CHO H 3232 + "CH CH OH ∆H°= −17 kcal/mole

Bond

Bond Energy (kcal/mole) 111 99 83 84 104

A. 79 kcal

B. 157 kcal

C. 173 kcal

D. 190 kcal

E. 277 kcal

OHCHCCCOHH

Part II: Specific Topics