Download Honors Chemistry- Chapter 16 Homework Packet Reaction Energy

Honors Chemistry- Chapter 16 Homework Packet
Reaction Energy
1) What is the difference between heat and temperature?
2) What device(s) do you use to measure temperature and heat?
3) A 250 gram sample of aluminum metal starts at 25.0°C. After being heated, its
temperature rises to 32.5°C. How much heat energy did the aluminum absorb?
(Cp (Al) = 0.897 J/g°C)
4) 2.5 kJ of heat energy is added to a 75 gram sample of copper metal. If the metal
starts at a temperature of 45°C, what will the final temperature of the copper
metal be? (Cp (Cu) = 0.385 J/g°C).
5) A 5.0 kg sample of benzene liquid starts at 30°C. After adding 130,500 J of heat
energy, its temperature rises to 45°C. What is the heat capacity of benzene,
including correct units?
6) For each equation below, determine H and whether the reaction is endothermic
or exothermic.
CH4 (g) + 2 O2 (g) → CO2 (g) + 2 H2O (l) + 890 kJ.
(a)
H =
Reaction is
CaCO3 (s) + 176 kJ → CaO (s) + CO2 (g)
(b)

H =
Reaction is
7) Rewrite each equation below with the H value included in the equation as either
a reactant or a product. Identify each as exothermic or endothermic.
H = -1200 kJ
(a)
2 Mg (s) + O2 (g) → 2 MgO (s)
(b)
2 Fe (s) + 3 CO2 (g) → 3 CO (g) + Fe2O3 (s)
H = 24.7 kJ
8) Using Hess’s Law, calculate Hreaction for the following reaction. Do not use a
calculator.
2 KCl (s) + 3 O2 (g)  2 KClO3 (s)
given the following data:
K (s) + ½ Cl2 (g)  KCl (s)
Hf = x
K (s) + ½ Cl2 (g) + 3/2 O2 (g)  KClO3 (s)
Hf = y
9) Using Hess’s Law, calculate Hreaction for the following reaction:
2 C (s) + H2 (g)  C2H2 (g)
given the following data:
C2H2 (g) + 5/2 O2 (g)  2 CO2 (g) + H2O (l)
H = -1300 kJ.
C (s) + O2 (g)  CO2 (g)
H = -394 kJ.
H2 (g) + ½ O2 (g)  H2O (l)
H = -286 kJ.
10) (a) What does it mean when we say that a chemical reaction is spontaneous?
(c) Give an example of a spontaneous chemical reaction that was not discussed
in class.
11) What is entropy?
12) What are the two forces that drive spontaneous reactions?
13) What is the sign of S for the following reactions or processes?
(a) CO (g) + 2 H2 (g) → CH3OH (g)
(b) H2O (l) → H2O (s)
(c) 2 C2H6 (g) + 7 O2 (g) → 4 CO2 (g) + 6 H2O (g)
(d) Na3PO4 (s) → 3 Na+ (aq) + PO43- (aq)
14) Calculate G for the following reactions. State whether each reaction is
spontaneous or not based on your numerical answer.
(a) H = -76 kJ
S = -117 J/K
T = 25°C
(b) H = 98 kJ
S = 292 J/K
T = 50°C
15) The S for the reaction shown below at 25°C is 217 J/mol K. Calculate G for
the reaction and determine if it is spontaneous or not at this temperature.
C (s) + O2 (g) → CO2 (g) + 393 kJ
16) Consider the melting of chloroform, CHCl3, as shown below.
CHCl3 (s) → CHCl3 (l)
If H = 98 kJ and S = 292 J/K, at what temperatures will chloroform
spontaneously melt?