Hess' Law

Q. Pick an ether which cannot be prepared by direct Williamson's synthesis:

1. $(C{H}_3{)}_{3}C–O–C_2{H}_5$
2. $C{H}_{3}C{H}_{2}C{H}_2–O–C{H}_{2}C{H}_{2}C{H}_3$
3. $Ph–O–C{H}_{2}C{H}_3$
4. $C{H}_{3}CH=CH–O–CH=C{H}_2$

Q.

The following reaction is an example of

${\mathrm{CH}}_4+2{\mathrm{O}}_2\to {\mathrm{CO}}_2+2{\mathrm{H}}_2\mathrm{O}+\mathrm{heat}+\mathrm{light}$

1. Addition reaction

2. Substitution reaction

3. Combustion reaction

4. Displacement reaction

Q. ZnO turns yellow on heating. Why?

Q.

If at 298 K the bond energies of C - H, C - C, C=C and H - H bonds are respectively 414, 347, 615 and 435 kJ $mo{l}^{-1}$, the value of enthalpy change for the reaction
$C{H}_2=C{H}_2\left(g\right)+H_2\left(g\right)\to C{H}_3-C{H}_3$ is:

1. -250 kJ

2. +125 kJ

3. -125 kJ

4. +250 kJ

Q. Calculate the lattice enthalpy of $KCl$ from the following data at standard states-
Enthalpy of sublimation of $K=89kJmo{l}^{-1}$
Enthalpy of dissociation of $C{l}_2=244kJmo{l}^{-1}$
Ionisation energy of $K=425kJmo{l}^{-1}$
Electron gain enthalpy of $Cl=-355kJmo{l}^{-1}$
Enthalpy of formation of $KCl=-438kJmo{l}^{-1}$

1. $719kJmo{l}^{-1}$
2. $-719kJmo{l}^{-1}$
3. $-832kJmo{l}^{-1}$
4. $832kJmo{l}^{-1}$

Q. Which of the following compounds would be hydrolysed most easily?

1. $C_2{H}_{5}Br$
2. $C{H}_{3}Br$
3. $C{H}_2=CH-Br$
4. $C{H}_2=CH-C{H}_2-Br$

Q.

Define the order of reaction?

Q.

Use the following data to calculate ${\Delta }_{lattic}{H}^{\ominus }$ for NaBr. ${\Delta }_{sub}{H}^{\ominus }$ for sodium metal = 108.4 kJ $mo{l}^{-1}$, ionisation enthalpy of sodium = 496 kJ $mo{l}^{-1}$, electron gain enthalpy of bromine = -325 kJ $mo{l}^{-1}$, bond dissociation enthalpy of bromine = 192 kJ $mo{l}^{-1}$, ${\Delta }_f{H}^{\ominus }$ for NaBr(s) = -360. 1 kJ $mo{l}^{-1}$

Q. 31. The reaction A(g)+2B(g)------>C(g)+D(g) is an elementary process. In an experiment the initial pressure of A and B are 0.6 and 0.8 atm respectively. When partial pressure of C is 0.2 atm, find the rate of reaction relative to the initial rate.

Q.

A chemical reaction was carried out at 300K and 280K. The rate conatants were found to be K₁ and K₂ respectively. Then

1)K₂ = 4 K₁

2)K₂ =2 K₁

3)K₂ = 0.5 K₁

4)K₂ = 0.25 K₁

Q.

$2\mathrm{NO}\left(\mathrm{g}\right)+\mathrm{Cl}\left(\mathrm{g}\right)\to 2\mathrm{NOCl}\left(\mathrm{s}\right):$ This reaction was studied at$–10°\mathrm{C}$ and the following data was obtained.

${\left[\mathrm{NO}\right]}_0$ and ${\left[{\mathrm{Cl}}_2\right]}_0$ are the initial concentrations and ${\mathrm{r}}_0$ is the initial reaction rate. The overall order of the reaction is _________. (Round off to the Nearest Integer).

Q. The enthalpy change for a reaction $N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)$ is -92.2 kJ/mol. Calculate the enthalpy of formation of ammonia.

1. -92.2 kJ/mol
2. -46.1 kJ/mol
3. 46.1 kJ/mol
4. -92.2 kJ/mol

Q. The lattice energy of solid $KCl$ is 181 kcal/mol. The enthalpy of solution of $KCl$ in water is 1 kcal/mol. If the hydration enthalpies of potassium and chloride ions are in the ratio $2:1$, what is the hydration enthalpy (kcal/mol) of potassium ions?

Q. If the enthalpy of hydrogenation of $C_6{H}_6\left(l\right)$ into $C_6{H}_{12}\left(l\right)$ is - 205 kJ and the resonance energy of $C_6{H}_6\left(l\right)$ is -152 kJ/mol then the enthalpy of hydrogenation of cyclohexene is: (Assume $\Delta H_{vap}$ of $C_6{H}_6\left(l\right),C_6{H}_8\left(l\right),C_6{H}_{12}\left(l\right)$ all are equal).

1. $-535.5\text{kJ/mol}$
2. $-238\text{kJ/mol}$
3. $-357\text{kJ/mol}$
4. $-119\text{kJ/mol}$

Q.

The enthalpies of formation of $A{l}_2{O}_3$ and $C{r}_2{O}_3$ are $-1569KJ$ and $-1134KJ$ respectively. $\Delta H$ for the reaction

$2Al+C{r}_2{O}_3\to 2Cr+A{l}_2{O}_3$ is

1. $-2730KJ$
2. $-462KJ$
3. $-1365KJ$
4. $+2730KJ$

Q.

Calculate the standard internal energy change for the reaction at 25⁰C:-

C₂H₄(g) + 3O₂(g)----------à 2CO₂ (g) + 2H₂O (l) DH for C₂H₄ (g) = 52.30 kJ/mole,

CO₂ = - 393.5 kJ/mole H₂O = - 286 kJ/mole R = 8.314 J/K/mole.

Q. How many steps are involved in Born Haber cycle for sodium chloride?

1. 4
2. 6
3. 7
4. 5

Q. In the Born Haber cycle for the formation of solid common salt ($NaCl$), the largest contribution comes from:

1. The low ionisation potential of $Na$
2. The high electron affinity of $Cl$
3. The Lattice energy
4. The low $\Delta H_{vap}$ of $Na\left(s\right)$

Q.

Enthalpy is an extensive property. In general, if enthalpy of an overall reaction A $\to$ B along one route is ${\Delta }_{r}H$ and ${\Delta }_{r}Hand{\Delta }_r{H}_1,{\Delta }_r{H}_2,{\Delta }_r{H}_3\cdots$ represent enthalpies of intermediate reactions leading to product B. What will be the relation between ${\Delta }_{r}H$ overall reaction and ${\Delta }_r{H}_1,{\Delta }_r{H}_2\cdots$ etc for intermediate reactions.

Q. “The resultant heat change in a reaction is the same whether it takes place in one or several stages.” This statement is called

1. Lavoisier and Laplace law
2. Hess's law
3. Joule's law
4. Le–chatelier's principle

Q.

The molar entropies of $HI\left(g\right),H\left(g\right)$ and $I\left(g\right)$ at $298K$ are $206.5,114.6$, and $180.7Jmol{e}^{-1}{K}^{-1}$ respectively. Using the $\Delta G^0$ given below, Calculate the bond energy of HI.

$H\left(g\right)\to H\left(g\right)+I\left(g\right)$; $\Delta G^0=271.8kJ$

1. 282.4 kj/mole

2. 298.3 kJ/mole

3. 100 kJ/mole

4. 32.17kJ/mole

Q.

Which Reaction is Exothermic?

Q.

How much energy will $1kg$mass of wood yield on complete combustion if its calorific value were $18kJ{g}^{-1}$?

Q. Hess' law is related to

1. Change in enthalpy during the reaction
2. Equilibrium constant
3. Infulence of pressure on volume
4. Rate of reaction

Q. what is the product when tertiary butyl benzene is oxidised b KMnO4?

Q. In a closed system A(s) gives 2B(g) +3C (g) if the partial pressure of c is doubled then the partial pressure of b will be

Q. Hess's law is also known as

1. Law of constant heat summation
2. Law of constant heat of enthalpy
3. Law of constant heat capacity
4. None of these

Q. Hess's law is also known as

1. Law of constant heat summation
2. Law of constant heat of enthalpy
3. None of these
4. Law of constant heat capacity

Q. Born-Haber cycle may be used to

1. to find out electron affinity of non-metal atom
2. both (a) and (b) above.
3. to find out lattice energy of the ionic compounds
4. for the preparation of ammonia in industries

Q. In the Born Haber cycle for the formation of solid common salt ($NaCl$), the largest contribution comes from:

1. The low ionisation potential of $Na$
2. The high electron affinity of $Cl$
3. The low $\Delta H_{vap}$ of $Na\left(s\right)$
4. The Lattice energy