Heat of Formation
Trending Questions
The standard enthalpy of formation of NH3 is 46.0 kJ mol−1. If the enthalpy of formation of H2 from its atom is −436 kJ mol−1 and that of N2 is −712 kJ mol−1, the average bond enthalpy of N−H bond in NH3 is
- −964 kJ mol−1
- +352 kJ mol−1
- +1056 kJ mol−1
- −1102 kJ mol−1
N2H4(l)+2H2O2(l)→N2(g)+4H2O(l);
△rHo1=−818 kJ/mol
N2H4(l)+O2(g)→N2(g)+2H2O(l); △rHo2=−622 kJ/mol
H2(g)+12O2(g)→H2O(l);△fHo3=−285 kJ/mol
- - 384 kJ/mol
- -187 kJ/mol
- -472 kJ/mol
- None of these
- 2C(diamond)+2H2(g)→C2H4(g)
- 2C(graphite)+2H2(g)→C2H4(g)
- 2C(diamond)+4H(g)→C2H4(g)
- 2C(graphite)+4H(g)→C2H4(g)
Lattice energy depends on:
Only on the radius of cation
Only of radius of the anion
Cation to anion radius ratio
Sum of the radii of cation and anion
12H2(g)+12Cl2(g)→HCl(g) is called
- Enthalpy of combustion
- Enthalpy of sublimation
- Enthalpy of formation
- Enthalpy of fusion
- 2y−x+z
- x−2y+z
- x+2y−z
- x+y+z
- 1.41×10−5 M
- 4×10−6 M
- 9.5×10−12 M
- 7.07×10−10 M
C(s)+O2(g)→CO2(g) ΔH=−94.0 kcal
H2(g)+12O2(g)→H2O(l) ΔH=−68.0 kcal
CH3COOH(l)+2O2(g)→2CO2(g)+2H2O(l) ΔH=−210.0 kcal
the heat of formation of acetic acid is :
- 116 kcal
- -116 kcal
- -114 kcal
- 114 kcal
Enthalpy of formation of caesium oxide =−233 kJ/mol
Enthalpy of sublimation of Cs=+78 kJ/mol
First ionization energy of Cs=+375 kJ/mol
Enthalpy of dissociation of O2 (g)=494 kJ/mol
First electron affinity of O=−141 kJ/mol
Second electron affinity of O=+845 kJ/mol
- −2090 kJ/mol
- 2090 kJ/mol
- −2290 kJ/mol
- −2390 kJ/mol
- AlCl3 would remain covalent in aqueous solution
- Only at infinite dilution AlCl3 undergoes ionisation
- In aqueous solution AlCl3 becomes ionic
- None of these
Enthalpy of sublimation for Mg(s)→Mg(g)=146.4 kJ mol−1
Enthalpy of dissociation of F2(g)→2F(g)=155.8 kJ mol−1
Ionisation energy of Mg(g)→Mg2+(g)=2186 kJ mol−1
Electron gain enthalpy of 2F→2F−1=2×−322.6=−645.2 kJ mol−1
Lattice enthalpy of MgF2=−2922.5 kJ mol−1
- −1079.5 kJmol−1
- 1099.5 kJmol−1
- 2200 kJmol−1
- 2200 kJmol−1
The standard enthalpies of formation of CO2(g), H2O(l) and glucose(s) at 25∘C are −400 kJ/mol, −300 kJ/mol and −1300 kJ/mol, respectively. The standard enthalpy of combustion per gram of glucose at 25∘C is
- + 2900 kJ
- −2900 kJ
- −16.11 kJ
- +16.11 kJ
The enthalpy of formation of methane at constant pressure and 300K is −75.83KJ. What will be the heat of formation at constant volume? (R=8.3JK−1mol−1)
-73.34 kJ
73.34 kJ
72.34 kJ
-72.34 kJ
- 490.2 kJ/mol
- −490.2 kJ/mol
- 390.2 kJ/mol
- −390.2 kJ/mol
- 490.2 kJ/mol
- −490.2 kJ/mol
- 390.2 kJ/mol
- −390.2 kJ/mol
- −269.9 kJ/mol
- −358.5 kJ/mol
- −508.9 kJ/mol
- −208.1 kJ/mol
Heat of vaporization of liquid methyl alcohol = 38 kJ mol−1 .
Heat of formation of gaseous atoms from the elements in their standard states:
H=218 kJ mol−1, C=715 kJ mol−1, O=249 kJ mol−1
Average bond energies :
C−H=415 kJ mol−1 C−O=356 kJ mol−1 O−H=463 kJ mol−1
- −256 kJ mol−1
- +266 kJ mol−1
- −266 kJ mol−1
- +256 kJ mol−1
- 805
- 35973
- 22.4
- 3121
C(s)+O2(g)→CO2(g) ΔH=−94.0 kcal
H2(g)+12O2(g)→H2O(l) ΔH=−68.0 kcal
CH3COOH(l)+2O2(g)→2CO2(g)+2H2O(l) ΔH=−210.0 kcal
the heat of formation of acetic acid is :
- 116 kcal
- -116 kcal
- -114 kcal
- 114 kcal
O−(g)+e−(g)→O2−(g).
Heat of sublimation of Mg(s)=147.7 kJ/mol
Ionisation energy of Mg(g) to form
Mg2+(g)=2189 kJ/mol
Bond dissociation energy for O2 =498.4 kJ/mol
First electron affinity of O(g)=−141 kJ/mol
Heat formation of MgO(s)=−601.7 kJ/mol
lattice energy of MgO=−3791 kJ/mol
- 601.7 kJ/mol
- 744.4 kJ/mol
- 1346.1 kJ/mol
- 147.7 kJ/mol
ΔfHo for white phosphorus has been taken to be zero, whereas black phosphorus is the most stable allotrope of phosphorus and this is the only exception.
REASON:
The reference standard state of white phosphorus is taken despite the fact that this form is not the most stable allotrope but simply the most reproducible form of phosphorus.
- Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
- Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
- Assertion is correct but Reason is incorrect
- Assertion incorrect but Reason is correct
4NH3(g)+3O2(g)→2N2(g)+6H2O(l)
at 298 K. Given that heat of formation of NH3(g) and H2O(l) are −46 kJ mol−1 and −286 kJ mol−1 respectively. Calculate heat of reaction at 298 K.
- −2232 kJmol−1
- −1532 kJmol−1
- −1852 kJmol−1
- −2832 kJmol−1
What will be the heat of formation of methane, if the heat of combustion of carbon is '-x' KJ, heat of formation of water is '-y' KJ and heat of combustion of methane '-Z' KJ?
(-x - y - z)
(-z - x + 2y) KJ
(-x - 2y - z) KJ
(-x - 2y + z) KJ
where, C(graphite)+O2(g)→CO2(g) ΔH=x kJ
C(diamond)+O2(g)→CO2(g) ΔH=y kJ
- x+y kJ/mole
- x−y kJ/mole
- y−x kJ/mole
- None of these
- C(diamond)+2H2(g)=CH4(g)
- C(graphite)+2H2(g)=CH4(l)
- C(graphite)+2H2(g)=CH4(g)
- C(graphite)+4H=CH4(g)
- 424 kJ mol−1
- 212 kJ mol−1
- −424 kJ mol−1
- −212 kJ mol−1
2H2(g)+O2(g)→2H2O(l) is ΔrHo=−572 kJmol−1
What will be the enthalpy of formation of H2O(l)?
- −286 kJmol−1
- 286 kJmol−1
- −1144 kJmol−1
- 1144 kJmol−1
12H2(g)+12Cl2(g)→HCl(g) is called
- Enthalpy of combustion
- Enthalpy of sublimation
- Enthalpy of formation
- Enthalpy of fusion
The enthalpies of combustion of carbon and carbon monoxide are −393.5 and −283 kJ mol−1 respectively. The enthalpy of formation of carbon monoxide per mole is
- −676.5 kJ
- 676.5 kJ
- 110.5 kJ
- −110.5 kJ
2C(s)→2C(g) △H=1410 kJ mol−1
H2(g)→2H(g) △H=330 kJ mol−1
- 1165
- 837
- 865
- 815