1. In the following experiment, a coffee-cup calorimeter containing 100 mL of H2
ID: 691840 • Letter: 1
Question
1. In the following experiment, a coffee-cup calorimeter containing 100 mL of H2O is used. The initial temperature of the calorimeter is 23.0 C. If 4.20 g of CaCl2 is added to the calorimeter, what will be the final temperature of the solution in the calorimeter? The heat of solution Hsoln of CaCl2 is 82.8 kJ/mol.
2. How many kilocalories are released when 215 g Cl2 reacts with silicon?
3. Assuming that Coca-Cola has the same specific heat as water [4.18 J/(gC)], calculate the amount of heat in kilojoules transferred when one can (about 350 g) is cooled from 30 C to 8 C.
4. When 25.0 mL of 1.0 M H2SO4 is added to 50.0 mL of 1.0 M NaOH at 25.0 C in a calorimeter, the temperature of the aqueous solution increases to 33.9 C.
Assuming that the specific heat of the solution is 4.18 J/(gC), that its density is 1.00 g/mL, and that the calorimeter itself absorbs a negligible amount of heat, calculate H in kilojoules for the reaction.
H2SO4(aq)+2NaOH2H2O(l)+Na2SO4(aq)
Explanation / Answer
1.
Mass of CaCl2 = 4.20 g.
Molar mass of CaCl2 = 40 + 2 (35.5) = 111 g/mol
Amount of CaCl2 = mass / molar mass = 4.20 / 111 = 0.0378 mol
Enthalphy of solution = q / n
82.8 = q / 0.0378
q = 3.13 kJ
But,
q = mass * specific heat of solution * (t2 - t1)
3.13 = 100 * 4.184 * (t2 - 23.0)
t2 - 23.0 = 0.00748
t2 = 23.007 0C
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