Advertisements
Advertisements
प्रश्न
Calculate the standard enthalpy of formation of liquid methanol from the following data:
- \[\ce{CH3OH_{(l)} + \frac{3}{2} O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\] ∆H° = – 726 kJ mol–1
- \[\ce{C_{(Graphite)} + O_{2(g)} -> CO_{2(g)}}\] ∆cH° = – 393 kJ mol–1
- \[\ce{H_{2(g)} + \frac{1}{2} O_{2(g)} -> H2O_{(l)}}\] ∆fH° = – 286 kJ mol–1
Advertisements
उत्तर
Given: Given equations are,
\[\ce{CH3OH_{(l)} + \frac{3}{2} O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\] ∆H° = – 726 kJ mol–1 ......(a)
\[\ce{C_{(Graphite)} + O_{2(g)} -> CO_{2(g)}}\] ∆cH° = – 393 kJ mol–1 .....(b)
\[\ce{H_{2(g)} + \frac{1}{2} O_{2(g)} -> H2O_{(l)}}\] ∆fH° = – 286 kJ mol–1 .....(c)
To find: The standard enthalpy of formation (∆fH°) of CH3OH(l)
Calculation: Required equation is,
\[\ce{C_{(graphite)} + 2H_{2(g)} + \frac{1}{2} O_{2 (g)} -> CH3OH_{(l)}}\]
Multiply equation (c) by 2 and add to equation (b),
| \[\ce{2H_{2(g)} + O_{2(g)} -> 2H2O_{(l)}}\], | ∆rH° = – 572 kJ mol–1 |
| \[\ce{C_{(graphite)} + O_{2(g)} -> CO_{2(g)}}\], | ∆cH° = – 393 kJ mol–1 |
| \[\ce{C_{(graphite)} + 2H_{2(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\] | |
∆rH° = – 572 – 393 = – 965 kJ mol–1 ….(d)
Reverse equation (a) and add to equation (d),
| \[\ce{CO_{2(g)} + 2H2O_{(l)} -> CH3OH_{(l)} + \frac{3}{2} O_{2(g)}}\], | ∆rH° = 726 kJ mol–1 |
| \[\ce{C_{(graphite)} + 2H_{2(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(l)}}\] | ∆rH° = – 965 kJ mol–1 |
| \[\ce{C_{(graphite)} + 2H_{2(g)} + \frac{1}{2} O_{2(g)} -> CH3OH_{(l)}}\] | |
∆fH° = ∆rH° = 726 – 965 = – 239 kJ mol–1
The standard enthalpy of formation (∆fH°) of CH3OH(l) from the given data is – 239 kJ mol–1
संबंधित प्रश्न
Answer the following in one or two sentences.
What is standard state of a substance?
Answer in brief.
How will you calculate reaction enthalpy from data on bond enthalpies?
Calculate enthalpy of formation of HCl if bond enthalpies of H2, Cl2 and HCl are 434 kJ mol-1, 242 kJ mol–1 and 431 kJ mol–1 respectively.
Calculate the standard enthalpy of combustion of CH4(g) if ΔfH°(CH4) = – 74.8 kJ mol–1, ΔfH°(CO2) = – 393.5 kJ mol–1 and ΔfH°(H2O) = – 285.8 kJ mol–1.
Does the following reaction represent a thermochemical equation?
\[\ce{CH_{4(g)} + 2O_{2(g)} -> CO_{2(g)} + 2H2O_{(g)}}\], ∆fH° = –900 kJ mol–1
The volume of oxygen required for complete combustion of 0.25 mole of methane at STP is ______.
The standard heats of formation in kcal mol−1 of NO2(g) and N2O4(g) are 8.0 and 2.0 respectively. The heat of dimerization of NO2 in kcal is ____________.
\[\ce{2NO2_{(g)} ⇌ N2O4_{(g)}}\]
The enthalpy change accompanying a reaction in which 1 mole of the substance in the standard state reacts completely with oxygen or is completely burnt is called as ____________.
lf, \[\ce{C_{(s)} + O2_{(g)} -> CO2_{(g)}}\], ∆H = x .........(i)
\[\ce{CO_{(g)} + 1/2O2_{(g)} -> CO2_{(g)}}\], ∆H = y .......(ii)
Then, the heat of formation of CO is:
\[\ce{S + 3/2O2 -> SO3 +2{x} kcal}\] .........(i)
\[\ce{SO2 + 1/2O2 -> SO3 + {y} kcal}\] .......(ii)
The heat of formation of SO2 is ____________.
Which among the following salts, solubility decreases with increase in temperature?
Enthalpy of formation of two compounds x and y are −84 kJ and −156 kJ respectively. Which of the following statements is CORRECT?
The enthalpy of formation of nitrogen dioxide is +33.2 kJ mol−1. The enthalpy of the reaction \[\ce{2N2_{(g)} + 4O2_{(g)} -> 4NO2_{(g)}}\]; is ____________.
Given that,
\[\ce{C_{(s)} + O_{2(g)} -> CO_{2(g)}}\] ΔH° = -X kJ
\[\ce{2CO_{(g)} + O_{2(g)} -> 2CO_{2(g)}}\] ΔH° = - Y kJ, then standard enthalpy of formation of carbon monoxide is ________.
From the following bond energies:
H – H bond energy: 431.37 kJ mol−1
C = C bond energy: 606.10 kJ mol−1
C – C bond energy: 336.49 kJ mol−1
C – H bond energy: 410.50 kJ mol−1
Enthalpy for the given reaction will be:
\[\begin{array}{cc}
\phantom{}\ce{H}\phantom{...}\ce{H}\phantom{...................}\ce{H}\phantom{...}\ce{H}\phantom{....}\\
\phantom{.}|\phantom{....}|\phantom{....................}|\phantom{....}|\phantom{.....}\\
\ce{C = C + H - H -> H - C - C - H}\\
\phantom{.}|\phantom{....}|\phantom{....................}|\phantom{....}|\phantom{.....}\\
\phantom{}\ce{H}\phantom{...}\ce{H}\phantom{...................}\ce{H}\phantom{...}\ce{H}\phantom{....}
\end{array}\]
Identify the invalid equation.
How many moles of helium gas occupies 22.4 Lat 0°c and at 1 atmospheric pressure?
What is enthalpy of formation of NH3 if bond enthalpies as (N ≡ N) = - 941 kJ/mol.
\[\ce{(H - H)}\] = 436 kJ/mol and \[\ce{(N - H)}\] = 389 kJ/mol?
When 0.5 gram of sulphur is burnt to form SO2, 4.6 kJ of heat liberated. Calculate enthalpy of formation of SO2(g). (Atomic mass : S = 32, O = 16)
Define and explain the term, enthalpy of reaction.
Calculate the standard enthalpy of the reaction, \[\ce{SiO2_{(s)} + 3C_{(graphite)} -> SiC_{(s)} + 2CO_{(g)}}\] from the following reactions:
- \[\ce{Si_{(s)} + O2_{(g)} -> SiO2_{(s)}}\], ΔrH0 = −911 kJ
- \[\ce{2C_{(graphite)} + O2_{(g)} -> 2CO_{(g)}}\], ΔrH0 = −221 kJ
- \[\ce{Si_{(s)} + C_{(graphite)} -> SiC_{(s)}}\], ΔrH0 = −65.3 kJ
Standard enthalpy of combustion of a substance is given. Then Write thermochemical equation.
ΔcH0[C2H5OH(1)] = - 1409 kJ mol-1
Standard enthalpy of combustion of a substance is given. Then Write thermochemical equation.
ΔcH0[CH3CHO(l)] = - 1166 kJ mol-1
The enthalpy of combustion of S (rhombic) is − 297 kJ mo1-1. Calculate the amount of sulphur required to produce 29. 74 kJ of heat.
Calculate the standard enthalpy of combustion of methane if the standard enthalpy of formation of methane, carbon dioxide and water are −74.8, −393.5 and −285.8 kJmol−1 respectively.
