Advertisements
Advertisements
Question
The enthalpy change for the reaction, \[\ce{C2H4_{(g)} + H2_{(g)} -> C2H6_{(g)}}\] is −620 J when 100 mL of ethylene and 100 ml of \[\ce{H2}\] react at 1 bar pressure. Calculate the pressure volume type of work and ΔU for the reaction.
Advertisements
Solution
Given:
Enthalpy change (ΔH) = −620 J
Volumes of reactants; \[\ce{C2H4}\] = 100 ml, \[\ce{H2}\] = 100 ml
Pressure (Pext) = 1 bar
To find:
Pressure volume work (W) and change in internal energy (ΔU) for the given reaction
Formulae:
- W = −Pext ΔV
- ΔH = ΔU + Pext ΔV
Calculation:
According to the equation of reaction 1 mole of \[\ce{C2H4}\] reacts with 1 mole of \[\ce{H2}\] to produce 1 mole of \[\ce{C2H6}\]. Hence, 100 ml of \[\ce{C2H4}\] would react with 100 ml of \[\ce{H2}\] to produce 100 ml of \[\ce{C2H6}\].
V1 = 100 mL + 100 mL = 200 mL = 0.2 dm3
V2 = 100 mL = 0.1 dm3
From formula (1),
W = −Pext ΔV
= −1 bar (0.1 dm3 − 0.2 dm3)
= 0.10 dm3 bar
= 0.10 dm3 bar × 100 `"J"/("dm"^3 "bar")` = + 10.00 J
∴ − Pext = ΔV = 10.00 J
∴ Pext = ΔV = −10.00 J
From formula (2),
ΔH = ΔU + Pext ΔV
∴ ΔU = ΔH − Pext ΔV
= −620 − (−10.00 J) = −610 J
Pressure volume work (W) = +10.00 J and ΔU = −610 J
APPEARS IN
RELATED QUESTIONS
Answer the following in one or two sentences.
What is standard state of a substance?
Answer the following question.
State Hess’s law of constant heat summation. Illustrate with an example. State its applications.
Answer the following question.
Calculate ΔrH° for the following reaction at 298 K:
1) 2H3BO3(aq) → B2O3(s) + 3H2O(l), ΔrH° = + 14.4 kJ
2) H3BO3(aq) → HBO2(aq) + H2O(l), ΔrH° = - 0.02 kJ
3) H2B4O7(s) → 2B2O3(s) + H2O(l), ΔrH° = + 17.3 kJ
The standard enthalpy of formation of water is - 286 kJ mol-1. Calculate the enthalpy change for the formation of 0.018 kg of water.
The enthalpy change of the following reaction:
\[\ce{CH_{4(g)} + Cl_{2(g)} -> CH3Cl_{(g)} + HCl_{(g)}ΔH^0 = –104 kJ}\]
Calculate C – Cl bond enthalpy. The bond enthalpies are:
| Bond | C − H | Cl − Cl | H − Cl |
| ∆H°/kJ mol−1 | 414 | 243 | 431 |
Calculate the standard enthalpy of the reaction.
\[\ce{2Fe_{(s)} + \frac{3}{2} O_{2(g)} -> Fe2O_{3(s)}}\]
Given:
| 1. | \[\ce{2Al_{(s)} + Fe2O_{3(s)} -> 2Fe_{(s)} + Al_2O_{3(s)}}\], | ∆rH° = –847.6 kJ |
| 2. | \[\ce{2Al_{(s)} + \frac{3}{2} O_{2(g)} -> Al2O_{3(s)}}\], | ∆rH° = –1670 kJ |
Write an application of Hess’s law.
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 ______.
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:
The heat evolved in the combustion of benzene is given by
\[\ce{C6H6 + 7 1/2O2 -> 6CO2_{(g)} + 3H2O_{(l)}}\]; ΔH = −3264.6 kJ
Which of the following quantities of heat energy will be evolved when 39 g C6H6 are burnt?
Given the reaction,
\[\ce{CH2O_{(g)} + O2_{(g)} -> CO2_{(g)} + H2O_{(g)}}\] ΔH = −527 kJ
How much heat will be evolved in the formation of 60 g of CO2?
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 ____________.
Standard enthalpy of formation of water is - 286 kJ mol-1. When 1800 mg of water is formed from its constituent elements in their standard states the amount of energy liberated is ______.
Standard entropies of N2(g), H2(g), and NH3(g) are a1, a2 and a3 J K-1 mol-1 respectively. What is value of ΔS° for formation of NH3(g)?
Identify the invalid equation.
What is the amount of water formed by the combustion of 1.6 g methane?
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)
Standard enthalpy of combustion of a substance is given. Then Write thermochemical equation.
ΔcH0[C2H5OH(1)] = - 1409 kJ mol-1
For the reaction, aA + bB → cC + dD, write the expression for enthalpy change of reaction in terms of enthalpies of formation of reactants and products.
Calculate heat evolved for combustion of 13 gm of acetylene (C2H2).
Given: \[\ce{C2H2_{(g)} + 5/2O_{2(g)}-> 2CO_{2(g)} + H2O_{(l)} \Delta_{(c)}H^{0} = - 1300 kJ}\]
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.
