Advertisements
Advertisements
प्रश्न
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
Advertisements
उत्तर
Given: Given equations are,
2H3BO3(aq) → B2O3(s) + 3H2O(l), ΔrH° = + 14.4 kJ ...(i)
H3BO3(aq) → HBO2(aq) + H2O(l), ΔrH° = - 0.02 kJ ....(ii)
H2B4O7(s) → 2B2O3(s) + H2O(l), ΔrH° = + 17.3 kJ .....(iii)
To find: The standard enthalpy of the given reaction (ΔrH°)
Calculation:
Reverse equation (i) and multiply by 2,
2B2O3(s) + 6H2O(l) → 4H3BO3(aq) , ΔrH° = - 28.8 kJ ......(iv)
Multiply equation (ii) by 4
4H3BO3(aq) → 4HBO2(aq) + 4H2O(l), ΔrH° = - 0.08 kJ .......(v)
Add equations (iv), (v) and (iii),
2B2O3(s) + 6H2O(l) → 4H3BO3(aq) , ΔrH° = - 28.8 kJ
4H3BO3(aq) → 4HBO2(aq) + 4H2O(l), ΔrH° = - 0.08 kJ
H2B4O7(s) → 2B2O3(s) + H2O(l), ΔrH° = + 17.3 kJ
_____________________________________________________
H2B4O7(s) + H2O(l) → 4HBO2(aq) ΔrH° = - 28.8 + (- 0.08) + 17.3 = - 11.58 kJ
The standard enthalpy (ΔrH°) of the given reaction is -11.58 kJ.
APPEARS IN
संबंधित प्रश्न
Answer in brief.
What is the standard enthalpy of combustion? Give an example.
Answer the following question.
State Hess’s law of constant heat summation. Illustrate with an example. State its applications.
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.
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.
Define the Standard enthalpy of combustion.
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.
Define the Bond enthalpy.
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 |
The heat of formations of CO(g) and CO2(g) are −26.4 kcal and −94.0 kcal respectively. The heat of combustion of carbon monoxide will be ____________.
Daily requirement of energy of a person is 'x' kJ. If heat of combustion of food material (Molecular mass = 100 g) is 'y' kJ, his daily consumption of the food in gram would be ____________.
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 ____________.
\[\ce{2NO2_{(g)} ⇌ N2O4_{(g)}}\]
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:
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 ____________.
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 ________.
Heat of formation of ethane, ethylene acetylene and carbon dioxide are - 136, - 66, - 228 and - 395 (all in kJ) respectively, most stable among them is ______.
Identify the invalid equation.
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?
The enthalpy change that accompanies a reaction in which 1 mole of its standard state is formed from its elements in their standard states
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
Standard enthalpy of combustion of a substance is given. Then Write thermochemical equation.
ΔcH0[CH3CHO(l)] = - 1166 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.
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.
The heat evolved in the combustion of 6.022 x 1021 carbon particles is 3.94 kJ. The heat of combustion of carbon is ______.
Calculate ΔsubH of the H2O from the given data:
\[\ce{H2O_{(s)}->H2O_{(l)},}\] ΔfusH = 6.01kJ mol−1
\[\ce{H2O_{(l)}-> H2O_{(g)},}\] ΔVapH = 45.07 kJ mol−1.
Heat of combustion of CH4(g) is -890 kJ/mole. What is the value of Δc H of 8gm of methane?
