Advertisements
Advertisements
Question
Calculate the standard enthalpy of formation of \[\ce{CH3OH_{(l)}}\] from the following data:
\[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)} }\]; ΔrH° = − 726 kJ mol-1
\[\ce{C_{(graphite)} + O2_{(g)} -> CO2_{(g)}}\]; ΔcH° = −393 kJ mol−1
\[\ce{H2_{(g)} + 1/2 O_{(g)} -> H2O_{(l)}}\]; ΔfH° = −286 kJ mol−1
Advertisements
Solution
Given: Given equations are,
\[\ce{CH3OH_{(l)} + 3/2 O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)} }\]; ΔrH° = − 726 kJ mol-1 ...(i)
\[\ce{C_{(graphite)} + O2_{(g)} -> CO2_{(g)}}\]; ΔcH° = −393 kJ mol−1 ...(ii)
\[\ce{H2_{(g)} + 1/2 O_{(g)} -> H2O_{(l)}}\]; ΔfH° = −286 kJ mol−1 ...(iii)
To find: The standard enthalpy of formation (ΔfH°) of \[\ce{CH3OH_{(l)}}\]
Calculation:
Required equation is, \[\ce{C_{(graphite)} + 2H2_{(g)} + 1/2 O2_{(g)} -> CH3OH_{(l)}}\]
Multiply equation (iii) by 2 and add to equation (ii),
\[\ce{2H2_{(g)} + O2_{(g)} -> 2H2O_{(l)}}\]; ΔfH° = −572 kJ mol−1
\[\ce{C_{(graphite)} + O2_{(g)} -> CO2_{(g)}}\]; ΔcH° = −393 kJ mol−1
________________________________________________________________________
\[\ce{C_{(graphite)} + 2H2_{(g)} + 2O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}}\], ΔrH° = −572 −393 = −965kJ mol−1 ...(iv)
Reverse equation (i) and add to equation (iv),
\[\ce{CO2_{(g)} + 2H2O_{(l)} -> CH3OH_{(l)} + 3/2O2_{(g)}}\], ΔrH° = − 726 kJ mol-1
\[\ce{C_{(graphite)} + 2H2_{(g)} + 2O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}}\], ΔrH° = −965
_____________________________________________________________________________
\[\ce{C_{(graphite)} + 2H2_{(g)} + 1/2O2_{(g)} -> CO2_{(g)} + CH3OH_{(l)}}\], ΔfH° = ΔrH° = 726 −965 = −239kJ mol−1
∴ The standard enthalpy of formation (ΔfH°) of \[\ce{CH3OH_{(l)}}\] from the given data is −239kJ mol−1
APPEARS IN
RELATED QUESTIONS
Answer in brief.
Obtain the expression for work done in chemical reaction.
Obtain the relationship between ΔH and ΔU for gas phase reactions.
Calculate the work done in the decomposition of 132 g of \[\ce{NH4NO3}\] at 100°C.
\[\ce{NH4NO3_{(s)} -> N2O_{(g)} + 2H2O_{(g)}}\]
State whether work is done on or by the system.
Answer the following question.
Calculate ΔU at 298 K for the reaction,
C2H4(g) + HCl(g) → C2H5Cl(g), ΔH = - 72.3 kJ
How much PV work is done?
An ideal gas expands from the volume of 1 × 10–3 m3 to 1 × 10–2 m3 at 300 K against a constant pressure at 1 × 105 Nm–2. The work done is
The work done by the liberated gas when 55.85 g of iron (molar mass 55.85 g mol–1) reacts with hydrochloric acid in an open beaker at 25°C
Calculate the enthalpy change for the reaction \[\ce{Fe2O3 + 3CO -> 2Fe + 3CO2}\] from the following data.
\[\ce{2Fe + 3/2O2 -> Fe2O3}\]; ΔH = −741 kJ
\[\ce{C + 1/2O2 -> CO}\]; ΔH = −137 kJ
\[\ce{C + O2-> CO2}\]; ΔH = −394.5 kJ
For which of the following ∆U = ∆H?
The difference between heats of reaction at constant pressure and at constanl volume for the reaction
\[\ce{2C6H6_{(l)} + 15O2_{(g)} -> 12CO2_{(g)} + 6H2O_{(l)}}\] at 25°C in kJ
When 6.0 g of O2 reacts with CIF as per \[\ce{2ClF_{(g)} + O2_{(g)} -> Cl2O_{(g)} + OF2_{(g)}}\] the enthalpy change is 38.55 kJ. The standard enthalpy of the reaction is ____________.
Identify the equation in which change in enthalpy is equal to change in internal energy.
When 4 g of iron is burnt to ferric oxide at constant pressure, 29.28 kJ of heat is evolved. What is the enthalpy of formation of ferric oxide?
(Atomic mass of Fe = 56)
The enthalpy change for two reactions are given by the equations
\[\ce{2Cr_{(s)} + 1.5 O2_{(g)} -> Cr2O3_{(s)}}\];
∆H1 = −1130 kJ ............(i)
\[\ce{C_{(s)} + 0.5 O2_{(g)} -> CO_{(g)}}\];
∆H2 = −110 kJ .........(ii)
What is the enthalpy change, in kJ, for the following reaction?
\[\ce{3C_{(s)} + Cr2O3_{(s)} -> 2Cr_{(s)} + 3CO_{(g)}}\]
Work done when 2 moles of an ideal gas is compressed from a volume of 5 m3 to 1 dm3 at 300 K, under a pressure of 100 kPa is ____________.
For the reaction, \[\ce{A_{(s)} + 2B_{(g)} -> 5C_{(s)} + D_{(l)}}\], ∆H and ∆U are related as ____________.
If 2 kJ of heat is released from system and 6 kJ of work is done on the system, what is enthalpy change of system?
For the reaction, \[\ce{N_{2(g)} + 3H_{2(g)} -> 2NH_{3(g)}}\], ΔH is equal to ______.
In which of the following reactions, ΔH is not equal to ΔU?
Under what conditions ΔH = ΔU?
Calculate ΔS of the surrounding if the standard enthalpy of formation of methanol is − 238.9 kJ mol−1.
Calculate work done in oxidation of 4 moles of SO2 at 25°C. (Given: R = 8.314 JK−1 mol−1 ).
Calculate the standard entropy change of the surrounding if standard enthalpy of formation of methyl alcohol is –240 kJ mol-1.
