Chapter 17 Assessment Problems – p.535
Sections 17-1, 17-2, 17-3
17-1
38. Law of Conservation of Energy – energy is conserved in every chemical and physical process.
39. Heat flows from the warmer object to the cooler. Ex. Holding a cold soft drink makes your hand cold.
40. Potential energy is stored in a substance because of its chemical make-up.
41. Chemical make-up and mass determine heat capacity (Q).
42. 1 Cal = 1000 calories = 1 kilocalorie
43.
a) 8.50 x 102 cal ÷ 1000 = 8.50 x 10 -1 Cal
b) 444 cal ÷ 0.2390 cal = 1.86 x 103 J
c) 1.8 kJ x 1000 = 1.8 x 103 J
d) 4.5 x 10 -1 kJ x 1000 = 450 J ÷ 4.184 J = 1.08 x 102 cal
44. Heat flow is measured in Thermochemistry across the boundary between the system and the
surroundings.
45.
( - ) = heat flow from the system to the surroundings (Exothermic)
( + ) = heat flow to the system from the surroundings (Endothermic)
46.
a) Exothermic
b) 2 substances = System; therefore beaker & air = surroundings (if 1 or both substances are in
water, the water is also a surrounding
47.
a) Condensation = Exothermic
b) Evaporation = Endothermic
c) Burning = Exothermic
d) Baking = Endothermic
17-2
48. Enthalpy = heat change at constant temperature
49. Calorimeters measure enthalpy changes in physical and chemical processes
50. Three errors in Foam Cup Calorimeters are:
- foam cup will absorb heat
- some heat will be lost to the air
- if reactants are not completely mixed, temperature measurements will be inaccurate
51. Bomb calorimeter = measures heat released at a constant temperature
52. Standard conditions for heat of combustion: 1 atmospheric pressure (101.3 kPa) & 25˚C.
53. Thermochemical equation = amount of heat released or absorbed in a chemical change at constant
pressure