The direct conversion of A to B is difficult and thus it is converted by path A$\to$C$\to$D$\to$B. Given

$∆{\mathrm{S}}_{\mathrm{A}\to \mathrm{C}}=50 \mathrm{e}.\mathrm{u}; ∆{\mathrm{S}}_{\mathrm{C}\to \mathrm{D}}=30 \mathrm{e}.\mathrm{u}; ∆{\mathrm{S}}_{\mathrm{B}\to \mathrm{D}}=20 \mathrm{e}.\mathrm{u}.$

(Where e.u. is the entropy unit)
then $∆{\mathrm{S}}_{\mathrm{A}\to \mathrm{B}}$ would be:

1. +60 e.u                                       

2. +100 e.u

3. -60 e.u                                       

4. -100 e.u

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 reaction,

$\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}=\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}+\mathrm{H}-\mathrm{H}\to \mathrm{H}-\stackrel{\stackrel{\mathrm{H}}{|}}{\underset{\underset{\mathrm{H}}{|}}{\mathrm{C}}}-\underset{\underset{\mathrm{H}}{|}}{\overset{\stackrel{\mathrm{H}}{|}}{\mathrm{C}}}-\mathrm{H}$

will be

1. 1523.6 kJ mol^-1

2. -243.6 kJ mol^-1

3. -120.0 kJ mol^-1

4. 553.0 kJ mol^-1

The enthalpy of neutralization of which of the following acids and bases is nearly –13.6 Kcal [Roorkee 1999]

(1) HCN and NaOH

(2) HCl and KOH

(3) HCl and HCN

(4) HCl and NH₄OH

The absolute enthalphy of neutralisation of the reaction $MgO\left(s\right)+2HCl\left(aq\right)\to MgC{l}_2\left(aq\right)+H_{2}O\left(l\right)$ will be [CBSE PMT 2005]

(1) Less than –57.33 kJ mol^–1

(2) –57.33 kJ mol^–1

(3) Greater than –57.33 kJ mol^–1

(4) 57.33 kJ mol^–1

Given that

$2C\left(s\right)+2O_2\left(g\right)\to 2C{O}_2\left(g\right);\Delta H=-787kJ$

$H_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to H_{2}O\left(l\right);\Delta H=-286kJ$

$C_2{H}_2\left(g\right)+2\frac{1}{2}{O}_2\left(g\right)\to 2C{O}_2\left(g\right)+H_{2}O\left(l\right);\Delta H=-1301kJ$

Heat of formation of acetylene is

(1) –1802 kJ

(2) +1802 kJ

(3) –800 kJ

(4) +228 kJ

The enthalpy of combustion at 25°C of H₂, cyclohexane (C₆H₁₂) and cyclohexene (C₆H₁₀) are –241, –3920 and –3800 KJ / mole respectively. The heat of hydrogenation of cyclohexene is

(1) – 121 KJ / mole

(2) + 121 KJ / mole

(3) – 242 KJ / mole

(4) + 242 KJ / mole

If (i) $C+O_2\to C{O}_2$, (ii) $C+1/2O_2\to CO$, (iii) $CO+1/2O_2\to C{O}_2$, the heats of reaction are Q, –12, –10 respectively. Then Q = [Orissa JEE 2004]

(1) – 2

(2) 2

(3) – 22

(4) – 16

The enthalpy of neutralization of HCN by NaOH is –12.13 kJ mol^–1. The enthalpy of ionisation of HCN will be -

1. 45.07 kJ

2. 4.310 kJ

3. 451.9 kJ

4. 33.77 kJ

If a chemical change is brought about by one or more methods in one or more steps, then the amount of heat absorbed or evolved during the complete course of reaction is same, which ever method was followed. This law is known as-

1. Le Chatelier's principle

2. Hess's law

3. Joule Thomson effect

4. Trouton's law

The heat of neutralisation of HCl by NaOH is -55.9 kJ/mole. If the heat of neutralisation of HCN by NaOH is -12.1 kJ/mole, then energy of dissociation of HCN is-

1. -43.8 kJ

2. 43.8 kJ

3. 68 kJ

4. -68 kJ