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WorksheetsHESS LAW AND ENTHALPIES
Total questions: 20
Worksheet time: 5hrs 0mins
Using the equations below:
C(s) + O2(g) → CO2(g) ∆H = –390 kJ
Mn(s) + O2(g) → MnO2(s) ∆H = –520 kJ
what is ∆H (in kJ) for the following reaction?
MnO2(s) + C(s) → Mn(s) + CO2(g)
910
130
-130
-910
Using the equations below
Cu(s) + 1/2O2(g) → CuO(s) ∆H = –156 kJ
2Cu(s) + O2(g) → Cu2O(s) ∆H = –170 kJ
what is the value of ∆H (in kJ) for the following reaction?
2CuO(s) → Cu2O(s) + 1/2O2(g)
142
15
-15
-142
The following equations show the oxidation of carbon and carbon monoxide to carbon dioxide.
C(s) +O2(g) → CO2(g) ΔH = –x kJ mol–1
CO(g) + O2(g) → CO2(g) ΔH = –y kJ mol–1
What is the enthalpy change, in kJ mol–1, for the oxidation of carbon to carbon monoxide?
C(s) + O2(g) → CO(g)
x + y
-x - y
y - x
x - y
Hess' Law makes use of which principle to calculate the enthalpy change of a reaction?
The law of conservation of energy
The law of conservation of matter
The law that you will always find a lost item in the last place you look for it
Murphy's law
Which of the following statements are true for the reaction:
SO2(g) + 1/2O2(g) ↔ SO3(g) ΔH = –92 kJ mol-1
Where ↔ indicates that the reaction can proceed in the forward and the reverse direction.
The forward and reverse reaction both produce 92 kJ of energy.
Oxidising 2 moles of SO2 would produce twice as much energy.
The reverse reaction has an enthalpy of +92 kJ mol-1.
Collecting the SO3 produced in the liquid state would not change the measured enthalpy.
In order to find the enthalpy of combustion of C3H8 how must the enthalpy changes be arranged?
ΔH3 = ΔH1 + ΔH2
ΔH2 = ΔH3 - ΔH1
ΔH1 = ΔH2 - ΔH3
0 = ΔH1 + ΔH2 + ΔH3
The standard enthalpy change of formation values of two oxides of phosphorus are:
P4(s) + 3O2(g) → P4O6(s) ΔHf = –1600 kJ mol–1
P4(s) + 5O2(g) → P4O10(s) ΔHf = –3000 kJ mol–1
What is the enthalpy change, in kJ mol–1, for the reaction below?
P4O6(s) + 2O2(g) → P4O10(s)
+4600
+1400
–1400
–4600
What is standard enthalpy of formation, ΔHfo?
Heat change when 1 mole of gaseous ions is hydrated in water at 25oC and 1 atm
Heat change when 1 mole of compound is formed from its elements in their standard states at 25oC and 1 atm
Heat change when 1 mole of gaseous atom is formed from its elements at 25oC and 1 atm
Heat change when 1 mole of electrons is removed from 1 mole of gaseous atoms at ground state at 25oC and 1 atm
Use the Hf values in the table below to answer the following question about the following reaction.
CO2(g) + N2(g) ⟶ NO(g) + CO(g) ΔH = ?
Formula kJ/mol
CO(g) -110
CO2(g) -394
NO(g) 90
a) Calculate Hrxn for the reaction.
370kJ/mol
374kJ/mol
333kJ/mol
335KJ/mol
3 C2H2(g) → C6H6(g)
What is the standard enthalphy change ΔHo, for the reaction represented above?
(ΔHof of C2H2(g) is 230 kJ mol-1;
(ΔHof of C6H6(g) is 83 kJ mol-1;)
-607 kJ
-147 kJ
-19 kJ
+19 kJ
+773 kJ
2 NH3(g) → 3 H2(g) + N2(g) ΔH°298 = 92 kJ/molrxn
According to the information above, what is the standard enthalpy of formation, ΔH°f , for NH3(g) at 298 K ?
-92 kJ/mol
-46 kJ/mol
46 kJ/mol
92 kJ/mol
184 kJ/mol
Based on the information in the table above, which of the following expressions gives the approximate ΔH° for the reaction represented by the following balanced chemical equation?
Fe2O3(s)+3 CO(g)→2 Fe(s)+3 CO2(g)
ΔH°rxn=[(0kJ/mol)+(−394kJ/mol)]−[(−826kJ/mol)+(−111kJ/mol)]
ΔH°rxn=[2(0kJ/mol)+ 3(−394kJ/mol)]−[(−826kJ/mol)+ 3(−111kJ/mol)]
ΔH°rxn=[(−826kJ/mol)+ 3(−111kJ/mol)]−[2(0kJ/mol)+ 3(−394kJ/mol)]
ΔH°rxn=[(−826kJ/mol)+(−111kJ/mol)]−[(0kJ/mol)+(−394kJ/mol)]
The enthalpy change for the reaction 2Al(s)+Fe2O3(s)→2Fe(s)+Al2O3(s) is −860kJ/mol. Based on the standard enthalpies of formation ΔH°f provided in the table, what is the approximate ΔH°f for Fe2O3(s) ?
+2540kJ/mol
−2540kJ/mol
+820kJ/mol
−820kJ/mol
4 NH3(g) + 3 O2(g) → 2 N2(g) + 6 H2O(g)
If the standard molar heats of formation of ammonia, NH3(g), and gaseous water, H2O(g), are -46 kJ/mol and -242 kJ/mol, respectively, what is the value of ΔH°298 for the reaction represented above?
-190 kJ/molrxn
-290 kJ/molrxn
-580 kJ/molrxn
-1,270 kJ/molrxn
-1,640 kJ/molrxn
Calculate ΔHrxn for the reaction of sulfur dioxide with oxygen. 2SO2(g) + O2(g) → 2SO3(g)
(ΔH0f (SO2) = –296.8 kJ/mol; ΔH0f (SO3) = –395.7 kJ/mol)
–98.9 kJ
–197.8 kJ
98.9 kJ
197.8 kJ
Calculate the energy released when 24.8 g Na2O reacts in the following reaction. Na2O(s) + 2HI(g) →2NaI(s) + H2O(l)
ΔH = –120.00 kcal
0.207 kcal
2.42 kcal
48.0 kcal
3.00 × 102 kcal
The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide, Al2O3(s), are –266 kJ mol–1 and –1676 kJ mol–1 respectively.
What is the enthalpy change under standard conditions for the following reaction?
3FeO(s) + 2Al (s) → 3Fe(s) + Al2O3(s)
+878kJ
–878kJ
–1942kJ
–2474kJ
Hydrocarbon fuel + oxygen ----> ___+____
(Select 2)
CO2
O2
H2O
CxHy
