To get credit…Students must show a formula, number set-up, and final answer with
the correct significant digits and units
1.
A piece of stainless steel weighing 1.55 g absorbs 141 J of heat energy when its
temperature increases by 178oC. What is the specific heat of stainless steel?
2.
The specific heat of olive oil is 2.0 J/g oC. When 435 J of heat is added to the olive
oil in a pan the temperature increases from 25oC to 110oC. What amount (mass) of
olive oil was placed into the saucepan?
3.
How many kilojoules (kJ) of heat are absorbed when 0.46 g of chloromethane
(C4H5Cl, boiling point 12.3oC) vaporizes at its boiling point? Chloromethane, ∆Hvap =
26.4 kJ/mol.
4.
How much energy in Calories (Cal) is needed to raise the temperature 49.32 g of
copper metal from 23.0oC to 137.0oC? (C=.20J/goC)
5.
Calculate the change in enthalpy (in kJ) for these reactions.
a.
CH4(g)
+ 2 O2(g)

CO2(g) +
2 H2O(l)
-74.86 kJ • 1 mol + 0.0 kJ• 2mol
-393.5 kJ • 1 mol + -285.8 kJ• 2 mol
mol
mol
mol
mol
∑Reactants = -74.86 kJ
∑Products = - 965.1 kJ
b. CaCO3(s)

-1207.0 kJ • 1 mol
mol
∑Reactants = - 1207.0 kJ
c.
6.
CaO(s)
+
CO2(g)
-635.1 kJ • 1 mol + -393.5 kJ• 1 mol
mol
mol
∑Products = - 1028.6 kJ
2 NO(g)
+
O2(g)

90.37 kJ • 2 mol + 0.0 kJ• 1mol
mol
mol
∑Reactants = + 180.74 kJ
List 5a, b, &c as endothermic or exothermic
2 NO2(g)
33.85 kJ • 2 mol
mol
∑Products =+ 67.7 kJ
7.
Determine which graph belongs to each equation in problem 5 (energy added (K.E.))
a.
b.
c.
8.
The combustion of ethane, C2H4, is an exothermic reaction.
C2H4(g)
+
3 O2(g)  2 CO2(g)
+
2 H2O(l) ∆H = -1.39 x 103J
Calculate the amount of heat liberated when 4.79 g of C 2H4 reacts with excess oxygen.
9.
Given the following reaction: C(s)
+
2 S(s) +
89.3 kJ

CS2(l)
How many grams of Carbon can be burned if 520.0 kJ of energy are available?
10.
What amount of energy is require to 40.0 grams of liquid water at room
temperature (23.0oC) and change it into 40.0 g of steam at 145.0 oC?
Formula q = m C Δ T
and q = m H?? and need values for . . .
specific heat(C) Cice= 2.09 J/goC
Cliquid= 4.18 J/goC
C steam= 1.67 J/goC
and the phase heats (H)
Hfus= 6.01 kJ/mol
Hvap=40.7 kJ/mol
Hint: 3 Steps!
CH4
+
2 O2
→
CO2
+
2 H 2O
11a.
If the previous reaction produces energy (- 357 kJ) is this an endo or exothermic
reaction?
11b.
Is the energy written on the reactant or product side of the equation?
11c.
If 15.0 grams of CH4 reacts with excess oxygen how much energy is produced?
12.
13.
14.
15.
In a specific heat lab, the lead releases heat, this is an _______ process, this energy
will have a _________ sign when calculated.
In a specific heat lab, the water in the Styrofoam cup absorbed heat, this is an
___________ process, this energy will have a _________ sign when calculated.
In the Cheeto Lab, the Cheeto was a good source of ________ Energy and released
heat, this is an _________ reaction, this energy will have a __________ sign .
In the Cheeto Lab, the water absorbed ________ Energy, this is an _________
process, this energy (qwater) will have a __________ sign when calculated.
16.
16a.
16b.
16c.
Using the phase diagram, a ______ exists at the lowest temp and highest pressure?
The ________ is where all three phases are in equilibrium
The line from the triple point between the liquid and gas phase is known as the
______________.
17.
Ammonia burns in the presence of a platinum catalyst to produce nitric oxide, NO.
4 NH3 (g) +
5 O2 (g)

4 NO (g)
+
6 H2O (g)
What is the heat of reaction at constant pressure? Use the following thermochemical
equations: N2 (g) +
O2 (g)

2 NO (g)
H = +180.6 kJ
N2 (g)
3 H2 (g)

2 NH3 (g)
H = -191.8 kJ
2 H2 (g)
O2 (g)

2 H2O (g)
H = -483.7 kJ
17a. How much energy is involved when 68 grams of Ammonia reacts with excess Oxygen?
1.
its
A piece of stainless steel weighing 1.55 g absorbs 141 J of heat energy when
temperature increases by 178oC. What is the specific heat of stainless steel?
q = m C Δ T so C = q
.
=
141 J .
= 0.511 J
o
mΔT
1.55 g (178 C)
g oC
2.
The specific heat of olive oil is 2.0 J/g oC. When 435 J of heat is added to the olive
oil in a pan the temperature increases from 25oC to 110oC. What amount (mass) of
olive oil was placed into the saucepan?
q=mCΔT
so m = q
.
.
= 2.6 g the unit g is in the
CΔT
denominator of the
denominator so it
is really in the numerator.
3.
How many kilojoules (kJ) of heat are absorbed when 0.46 g of chloromethane
(C4H5Cl, boiling point 12.3oC) vaporizes at its boiling point? Chloromethane, ∆Hvap =
26.4 kJ/mol. Change the liquid to gas/vapor, use the Hvap number
q = m Hvap
=
0.14 kJ
4.
How much energy in Calories (Cal) is needed to raise the temperature 49.32 g of
copper metal from 23.0oC to 137.0oC? (C=.20J/goC)
q = m C Δ T so q = 0.27 Cal
5.
Calculate the change in enthalpy ( kJ) for these reactions. (Use the chart on p. 530) and
the formula H = ∑Hfo Products - ∑Hfo Reactants
a.
CH4(g)
+ 2 O2(g)

CO2(g) +
2 H2O(l)
-74.86 kJ • 1 mol + 0.0 kJ• 2mol
-393.5 kJ • 1 mol + -285.8 kJ• 2 mol
mol
mol
mol
mol
∑Reactants = -74.86 kJ
∑Products = - 965.1 kJ
∆H = ∑Hfo Products - ∑Hfo Reactants
= - 965.1 kJ – ( - 74.86kJ)
= - 890.24 kJ
b. CaCO3(s)

-1207.0 kJ • 1 mol
mol
c.
CaO(s)
+
CO2(g)
-635.1 kJ • 1 mol + -393.5 kJ• 1 mol
mol
mol
= + 178.4 kJ
2 NO(g)
+
O2(g)

90.37 kJ • 2 mol + 0.0 kJ• 1mol
2 NO2(g)
33.85 kJ • 2 mol
= -113.04 kJ
6.
a.
exothermic (-)
b. endothermic (+)
c. exothermic (-)
7.
Sketch a graph plotting P.E. vs. Time (energy added (K.E.))
a.
b.
c.
8.
The combustion of ethane, C2H4, is an exothermic reaction.
C2H4(g)
+
3 O2(g)  2 CO2(g)
+
2 H2O(l) ∆H = -1.39 x 103J
Calculate the amount of heat liberated when 4.79 g of C 2H4 reacts with excess oxygen.
= 0.238 kJ
9.
Given the following reaction: C(s)
+
2 S(s) +
89.3 kJ

CS2(l)
How many grams of Carbon can be burned if 520.0 kJ of energy are available?
= 69.9 g Carbon
10.
What amount of energy is require to 40.0 grams of liquid water at room
temperature (23.0oC) and change it into 40.0 g of steam at 145.0 oC?
Formula q = m C Δ T
and q = m H?? and need values for . . .
specific heat(C) Cice= 2.09 J/goC
Cliquid= 4.18 J/goC
C steam= 1.67 J/goC
and the phase heats (H)
Hfus= 6.01 kJ/mol
Hvap=40.7 kJ/mol
Starting with the T = 23.0oC the water is liquid need to use the Cliquid = 4.18 J/goC,
to change it to liquid water at 100.0oC (Δ T = 77.0oC).
q= mCΔT
q = (40.0 g) • (4.18 J) • (77.0oC) x ( 1 kJ ) = 12.9 kJ
g oC
1000 J
Change the liquid water to steam (gas), use the Hvap number
q = m Hvap
q = (40.0 g) • (40.7 kJ) x ( 1 mol ) =
90.4 kJ
mol
18.0 g
Now gas at a T = 100.0oC and need to use the Csteam = 1.67 J/goC, to change it to
steam at 145oC (Δ T = 45.0oC).
q= mCΔT
q = (40.0 g) • (1.67 J) • (45.0oC) x ( 1 kJ ) = 3.01 kJ
g oC
1000 J
To determine the total energy the values need to be added together:
12.9 kJ +
90.4 kJ + 3.01 kJ = 106.3 kJ need correct sig figs and unit
11a.
11b.
11c.
12.
13.
14.
15.
If the following reaction produces energy (- 357 kJ) is this an endo or exothermic
reaction? Exothermic, you can tell by the negative sign.
Is the energy written on the reactant or product side of the equation?
The energy should be written on the product side (energy out)
CH4
+
2 O2
→
CO2
+
2 H2O + 357 kJ
If 15.0 grams of CH4 reacts with excess oxygen how much energy is produced?
= 335 kJ (Hint: Must convert CH4 to moles and use the mole ratio)
In the specific heat lab, the lead released heat, this is an _exothemic _ process, this
energy will have a _negative (-) _ sign when calculated.
In a specific heat lab, the water in the Styrofoam cup absorbed heat, this is an
_endothermic__ process, this energy will have a __postive (+)__ sign when calculated.
In the Cheeto Lab, the cheeto was a good source of _Potential_ Energy and released
heat, this is an _exothemic _ reaction, this energy will have a _negative (-)_ sign .
In the Cheeto Lab, the water absorbed _thermal_ Energy, this is an __exothermic__
process, this energy (qwater) will have a _positive (+)_ sign when calculated.
16.
16a.
16b.
16c.
17.
Using the phase diagram, a Solid exists at the lowest temp and highest pressure?
The triple point is where all three phases are in equilibrium.
The line from the triple point between the liquid and gas phase is known as the
boiling point.
Ammonia burns in the presence of a platinum catalyst to produce nitric oxide, NO.
4 NH3 (g) +
5 O2 (g)

4 NO (g)
+
6 H2O (g) GOAL
What is the heat of reaction at constant pressure? Use the following thermochemical
equations: N2 (g) +
O2 (g)

2 NO (g)
H = +180.6 kJ Double it
N2 (g)
3 H2 (g)

2 NH3 (g)
H = -191.8 kJ Flip & double it
2 H2 (g)
O2 (g)

2 H2O (g)
H = -483.7 kJ Triple it
Think of the three equations above as puzzle pieces that have to be arranged to get to the goal equation.
2
4
6
2
N2 (g) + 2 O2(g)  4 NO (g)
H = 180.6 kJ (2)
= + 361.2 kJ
NH3 (g)
 2 N2 (g) + 6 H2 (g)
H = - 191.8 kJ ( -2) = + 383.6 kJ
H2 (g) + 3 O2 (g)  6 H2O (g)
H = -483.7 kJ (3)
= - 1451.1 kJ
N2 + 6 H2 + 4 NH3 + 5 O2  4 NO + 2 N2 + 6 H2 + 6 H2O
- 706.3 kJ
How much energy is involved when 68 grams of Ammonia reacts with excess Oxygen?
= -710 kJ or -7.1 x 102 k
(Hint: Use mole ratio!)