1. Given: NH3(g) + O2(g) = N2(g) + H2O(g)
We can break this equation down into two steps:
Step 1: NH3(g) = 1.5 H2(g) + 0.5 N2(g)
Step 2: 0.5 H2(g) + 0.5 O2(g) = H2O(g)
To find the overall enthalpy change, we need to add the enthalpy changes of the individual steps. Remember to multiply the enthalpy change of each step by a factor if necessary.
Step 1: ΔH1 = ΔHf(N2(g)) + 0.5 ΔHf(H2(g)) - ΔHf(NH3(g))
Step 2: ΔH2 = ΔHf(H2O(g)) - 0.5 ΔHf(H2(g)) - 0.5 ΔHf(O2(g))
Overall enthalpy change: ΔH = ΔH1 + ΔH2
2. Given: NO(g) + O2(g) = NO2(g)
To find the overall enthalpy change, we need to look for the reverse reaction of one of the given reactions. In this case, we can use Reaction 3 from the question.
Reverse of Reaction 3: SO2(g) + H2O(g) + O2(g) = H2SO4(l)
Since the desired reaction is the reverse of Reaction 3, the enthalpy change will be the opposite of the enthalpy change of Reaction 3.
ΔH = -ΔH(Reaction 3)
3. Given: H2SO4(l) = SO2(g) + H2O(g) + O2(g)
To find the overall enthalpy change, we can use the given reaction directly.
ΔH = ΔHf(SO2(g)) + ΔHf(H2O(g)) + ΔHf(O2(g)) - ΔHf(H2SO4(l))
4. Given: Mg(s) + CO2(g) = MgO(s) + C(s)
We can break this equation down into two steps:
Step 1: Mg(s) = MgO(s)
Step 2: C(s) + O2(g) = CO2(g)
To find the overall enthalpy change, we need to add the enthalpy changes of the individual steps.
Step 1: ΔH1 = ΔHf(MgO(s)) - ΔHf(Mg(s))
Step 2: ΔH2 = ΔHf(CO2(g)) - ΔHf(C(s)) - ΔHf(O2(g))
Overall enthalpy change: ΔH = ΔH1 + ΔH2
5. Given: F2(g) + H2O(l) = HF(g) + O2(g)
We can break this equation down into two steps:
Step 1: F2(g) = 2F(g)
Step 2: 2F(g) + H2O(l) = 2HF(g) + O2(g)
To find the overall enthalpy change, we need to add the enthalpy changes of the individual steps. Remember to multiply the enthalpy change of each step by a factor if necessary.
Step 1: ΔH1 = 2ΔHf(F(g)) - ΔHf(F2(g))
Step 2: ΔH2 = 2ΔHf(HF(g)) + ΔHf(O2(g)) - 2ΔHf(F(g)) - ΔHf(H2O(l))
Overall enthalpy change: ΔH = ΔH1 + ΔH2
6. Given: C6H6(l) + O2(g) = CO2(g) + H2O(g)
To find the overall enthalpy change, we can use the given reaction directly.
ΔH = ΔHf(CO2(g)) + ΔHf(H2O(g)) - ΔHf(C6H6(l))
7. Given: NH3(g) + O2(g) = NO2(g) + H2O(g)
To find the overall enthalpy change, we can use the given reaction directly.
ΔH = ΔHf(NO2(g)) + ΔHf(H2O(g)) - ΔHf(NH3(g))
8. Given: CH4(g) + O2(g) = CO2(g) + H2O(l)
To find the overall enthalpy change, we need to look for the reverse reaction of one of the given reactions. In this case, we can use Reaction 6 from the question.
Reverse of Reaction 6: CO2(g) + H2O(g) = C6H6(l) + O2(g)
Since the desired reaction is the reverse of Reaction 6, the enthalpy change will be the opposite of the enthalpy change of Reaction 6.
ΔH = -ΔH(Reaction 6)
9. Given: H2S(g) + O2(g) = H2O(l) + SO2(g)
To find the overall enthalpy change, we can use the given reaction directly.
ΔH = ΔHf(H2O(l)) + ΔHf(SO2(g)) - ΔHf(H2S(g))
10. Given: CaO(s) + H2O(l) = Ca(OH)2(s)
To find the overall enthalpy change, we can use the given reaction directly.
ΔH = ΔHf(Ca(OH)2(s)) - ΔHf(CaO(s)) - ΔHf(H2O(l))
Grade 12 Chemistry
Use Hess's Law to find ΔH for the following reactions: Express your answers in kJ/mol of the first reactant on the left in each equation.
1. NH3(g) + O2(g) = N2(g) + H2O(g)
2.NO(g) + O2(g) = NO2(g)
3. H2SO4(I) = SO2(g) + H2O(g) + O2(g)
4. Mg(s) + CO2(g) = MgO(s) + C(s)
5. F2(g) + H2O(I) = HF(g) + O2(g)
6. C6H6(l) + O2(g) = CO2(g) + H2O(g)
7. NH3(g) + O2(g) = NO2(g)+H2O(g)
8. CH4(g) + O2(g) = CO2(g) + H2O(l)
9. H2S(g) + O2(g) = H2O(l) + SO2(g)
10 CaO(s) + H2O(l) = Ca (OH)2(s)
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