Chem Ch.5 &6.pdf - Chapter 5: Thermochemistry Exercises 5 ....

Chapter 5: Thermochemistry
Exercises
5 . Calculate the heat capacity, in joules and in calories per degree, of the following:
(a) 45.8 g of nitrogen gas
(b) 1.00 pound of aluminum metal
7 . How much heat, in joules and in calories, is required to heat a 28.4-g (1-oz) ice cube
from −23.0 °C to −1.0 °C?
9 . If 14.5 kJ of heat were added to 485 g of liquid water, how much would its
temperature increase?

11 . A piece of unknown solid substance weighs 437.2 g, and requires 8460 J to
increase its temperature from 19.3 °C to 68.9 °C.
(a) What is the specific heat of the substance?
(b) If it is one of the substances found in Table 5.1 , what is its likely identity?
19 . How much will the temperature of a cup (180 g) of coffee at 95 °C be reduced when
a 45 g silver spoon (specific heat 0.24 J/g °C) at 25 °C is placed in the coffee and the
two are allowed to reach the same temperature? Assume that the coffee has the same
density and specific heat as water.
21 . The temperature of the cooling water as it leaves the hot engine of an automobile is
240 °F. After it passes through the radiator it has a temperature of 175 °F. Calculate the
amount of heat transferred from the engine to the surroundings by one gallon of water
with a specific heat of 4.184 J/g °C.
27 . The addition of 3.15 g of Ba(OH)
2
·8H
2
O to a solution of 1.52 g of NH
4
SCN in 100 g
of water in a calorimeter caused the temperature to fall by 3.1 °C. Assuming the specific
heat of the solution and products is 4.20 J/g °C, calculate the approximate amount of
heat absorbed by the reaction, which can be represented by the following equation:
Ba(OH)
2
·8H
2
O( s ) + 2NH
4
SCN( aq ) ⟶ Ba(SCN)
2
( aq ) + 2NH
3
( aq ) + 10H
2
O( l)
q=mcΔT
q=(3.15g + 1.52g + 100g) x 4.20 x 3.1