Question

Using the following thermal chemical data (use Hess’s law)

2Fe(s) + 6HF(g) —> 2FeF3(s) + 3H2(g)

?rH•= -1787.4 kJ/mol

2Fe(s) + 6HCl(g) —> 2FeCl3(s) + 3H2(g)

?rH•= -1457.0 kJ/mol

calculate?rH• for the following reaction:

FeCl3(s) + 3HF(g) —> FeF3(s) + 3HCl(g)

2. when 19.86g NaOH is dissolved in 125 mL of water in the
coffee-cup calorimeter, the temperature rises from 23•C to 65•C.
what is the enthalpy change per mole of the hydroxide dissolved in
the water? Assume that the solution has a specific heat capacity of
4.18 J/gK

3. A 2.5 g sample but of octane (C8H18) is burned in a bomb
calorimeter containing 0.75 kg of water at an initial temperature
of 24•C. After the reaction, the final temperature of the water is
32•C. the heat capacity of the calorimeter is 923 J/•C. the
specific heat of water is 4.184 J/g•C. calculate the heat of
combustion of octane in kJ/mol.

Answer #1

Ans 1

The first reaction is

2Fe(s) + 6HF(g) —> 2FeF3(s) + 3H2(g)

multiply by 0.5

Fe(s) + 3HF(g) —> FeF3(s) + 1.5H2(g)

H1 = -1787.4*0.5 = - 893.7 kJ/mol

The second reaction is

2Fe(s) + 6HCl(g) —> 2FeCl3(s) + 3H2(g)

Reverse the reaction and multiply by 0.5

FeCl3(s) + 1.5H2(g) = Fe(s) + 3HCl(g)

H2 = 1457.0*0.5 = 728.5 kJ/mol

Add the two reactions

Fe(s) + 3HF(g) + FeCl3(s) + 1.5H2(g) —> FeF3(s) + 1.5H2(g) + Fe(s) + 3HCl(g)

FeCl3(s) + 3HF(g) —> FeF3(s) + 3HCl(g)

H = H1 + H2

= - 893.7 + 728.5

= - 165.2 kJ/mol

A 1.00 g sample of octane (C8H18) is burned in a calorimeter
that contains 1.20 kg of water. The temperature of the water and
the bomb rises from 25.00°C to 33.20°C. The heat capacity of the
bomb, Cbomb, is 837 J/0C . Specific heat for water: 4.184
Jg–1°C–1.
a) Calculate the amount of heat gained by the calorimeter
b) Calculate the amount of heat gained by the water
c) Calculate the amount of heat given off per mol of octane...

A 1.00g sample of octane (C8H18) is burned in a calorimeter that
contains 1.20kg of water. The temperature of the water and the bomb
rises from 25.00oC to 33.20oC. If the heat capacity of the bomb,
Cbomb, is 837J/K calculate the heat given off per mole of octane.
Specific heat for water: 4.184 J/g.°C
Please show work, correct equation to use and values. I know how
to calculate heat but not sure how to correctly find heat per
mole.
86...

In the laboratory a student burns a 1.17-g
sample of dimethyl oxalate
(C4H6O4) in a
bomb calorimeter containing 1070. g water. The
temperature increases from 24.60 °C to
27.70 °C. The specific heat capacity of water is
4.184 J g-1 °C-1.
The combustion enthalpy is −1675 kJ/mol
dimethyl oxalate.
C4H6O4(s) +
7/2 O2(g) 4
CO2(g) + 3 H2O(l)
ΔrH o = -1675 kJ/mol
Calculate the heat capacity of the calorimeter.
heat capacity of calorimeter =
J/°C

A 0.553-g sample of diphenyl
phthalate
(C20H14O4) is
burned in a bomb calorimeter and the temperature increases from
24.40 °C to 27.57 °C. The
calorimeter contains 1.08×103 g of
water and the bomb has a heat capacity of 877
J/°C. The heat capacity of water is 4.184 J
g-1°C-1. Based on this experiment, calculate
ΔE for the combustion reaction per mole of diphenyl
phthalate burned.
______ kJ/mol

A 0.373-g sample of naphthalene (C10H8) is burned in a bomb
calorimeter and the temperature increases from 24.90 °C to 27.80
°C. The calorimeter contains 1.05E3 g of water and the bomb has a
heat capacity of 836 J/°C. Based on this experiment, calculate ΔE
for the combustion reaction per mole of naphthalene burned
(kJ/mol).

A 0.287-g sample of bianthracene (C28H18) is burned in a bomb
calorimeter and the temperature increases from 25.30 °C to 27.50
°C. The calorimeter contains 1.03E3 g of water and the bomb has a
heat capacity of 856 J/°C. Based on this experiment, calculate ΔE
for the combustion reaction per mole of bianthracene burned
(kJ/mol).

When 1.020 g of ethanol (C2H6O, 46.07 g/mol) was burned in a
bomb calorimeter containing 2400. g of water, the temperature of
the water rose from 22.46 to 25.52ºC. The specific heat
of water is 4.18 J/g-°C. What is the enthalpy of combustion of 1
mol of ethanol? What is the heat capacity of the calorimeter?

When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup
calorimeter, the temperature rises from 25.18 ˚C to 47.53 ˚C.
Calculate the ∆Hrxn for the dissolution process. Assume that the
solution has a specific heat capacity of 4.184 J/gK

1.
A bomb calorimeter, or a constant
volume calorimeter, is a device often used to determine the heat of
combustion of fuels and the energy content of foods.
In an experiment, a 0.4137 g sample of
bianthracene
(C28H18) is burned
completely in a bomb calorimeter. The calorimeter is surrounded by
1.361×103 g of water. During the
combustion the temperature increases from 24.82 to
27.25 °C. The heat capacity of water is 4.184 J
g-1°C-1.
The heat capacity of the calorimeter...

Consider the reaction
C12H22O11(s)+12O2(g)→12CO2(g)+11H2O(l)
in which 10.0 g of sucrose, C12H22O11, was burned in a bomb
calorimeter with a heat capacity of 7.50 kJ/∘C. The temperature
increase inside the calorimeter was found to be 22.0 ∘C. Calculate
the change in internal energy, ΔE, for this reaction per
mole of sucrose.
Express the change in internal energy in kilojoules per mole to
three significant figures.
Hints
ΔE =
kJ/mol

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