List of practice Questions

For the process to occur under adiabatic conditions, the correct condition is:

The enthalpies of all elements in their standard states are:

\(∆U^Θ\) of combustion of methane is – \(X\ kJ \ mol^{–1}\). The value of \(∆H^Θ\) is

Calculate the number of kJ of heat necessary to raise the temperature of 60.0 g of aluminium from 35°C to 55°C. Molar heat capacity of Al is 24 J mol^–1 K^–1.

What is the relationship between the members of the following pairs of structures? Are they structural or geometrical isomers or resonance contributors?

Calculate the enthalpy change on freezing of \(1.0\ mol\) of water at \(10.0°C\) to ice at \(-10.0°C\). \(∆_{fus}H = 6.03\ kJ mol^{–1}\) at \(0°C\).
\(C_p [H_2O(l)] = 75.3\ J mol^{–1}K^{–1}\)
\(C_p [H_2O(s)] = 36.8 \ J mol^{–1}K^{–1}\)

For the following bond cleavages, use curved arrows to show the electron flow and classify each as homolysis or heterolysis. Identify reactive intermediate produced as free radical, carbocation and carbanion.

Explain the terms Inductive and Electromeric effects. Which electron displacement effect explains the following correct orders of acidity of the carboxylic acids? 
\((a) Cl_3CCOOH>Cl_2CHCOOH>ClCH_2COOH \)
\((b) CH_3CH_2COOH>(CH_3)_2CHCOOH>(CH_3)_3C.COOH.\)

In the estimation of sulphur by Carius method, 0.468 g of an organic sulphur compound afforded 0.668 g of barium sulphate. Find out the percentage of sulphur in the given compound.

Draw the resonance structures for the following compounds. Show the electron shift using curved-arrow notation. 
(a) \(C_6H_5OH \)
(b) \(C_6H_5NO_2\) 
(c) \( CH_3CH=CHCHO\) 
(d) \(C_6H_5–CHO \)
(e) \(C_6H_5–C+H_2\)
(f) \(CH_3CH=CH C+H_2\)

The best and latest technique for isolation, purification and separation of organic compounds is

The reaction of cyanamide, \(NH_2CN(s)\), with dioxygen was carried out in a bomb calorimeter, and \(∆U\) was found to be \(–742.7\ kJ\ mol^{–1}\) at \(298\ K\). Calculate enthalpy change for the reaction at \(298\ K\).
\(NH_2CN(g)+\frac 32O_2(g)→N_2(g)+CO_2(g)+H_2O(l)\)

In a process, 701 J of heat is absorbed by a system and 394 J of work is done by the system. What is the change in internal energy for the process?

Justify that the following reactions are redox reactions:

1. \(CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O(g) \)
2. \(Fe_2O_3(s) + 3CO(g) \rightarrow 2Fe(s) + 3CO_2(g) \)
3. \(4BCl_3(g) + 3LiAlH_4(s) \rightarrow 2B_2H_6(g) + 3LiCl(s) + 3 AlCl_3 (s) \)
4. \(2K(s) + F_2(g) \rightarrow 2K+F^- (s) \)
5. \(4 NH_3(g) + 5 O_2(g) \rightarrow 4NO(g) + 6H_2O(g)\)

Enthalpy of combustion of carbon to CO₂ is –393.5 kJ mol^–1. Calculate the heat released upon formation of 35.2 g of CO₂ from carbon and dioxygen gas.

The reaction CH₃CH₂I + KOH(aq) \(\rightarrow\) CH₃CH₂OH + KI is classified as 

Enthalpies of formation of CO(g), CO₂(g), N₂O(g) and N₂O₄(g) are –110, – 393, 81 and 9.7 kJ mol^-1 respectively. Find the value of ∆_rH for the reaction.
\(N_2O_4(g) + 3CO(g) → N_2O(g) + 3CO_2(g)\)

In the organic compound \(CH_2 = CH-CH_2-CH_2-C≡CH\), the pair of hydridised orbitals involved in the formation of \(C_2 – C_3\) bond is

Given, \(N_2(g) + 3H_2(g)→2NH_3(g)\); \(∆_rH^Θ=-92.4\ kJ mol^{–1}\)
What is the standard enthalpy of formation of \(NH_3\) gas?

Calculate the standard enthalpy of formation of \(CH_3OH(l)\) from the following data.
\(CH_3OH (l) +\frac 32 O_2(g)→CO_2(g)+2H_2O (l)\) ;  \( ∆_rH^Θ= –726 \ kJ mol^{–1}\),
\(C(graphite)+O_2(g)→CO_2(g)\);  \(∆_cH^Θ = –393 \ kJ mol^{–1}\),
\(H_2(g)+\frac 12 O_2(g)→H_2O (l)\);  \(∆_f H^Θ= –286 kJ mol^{–1}\)

Calculate the enthalpy change for the process
\(CCl_4(g) → C(g) + 4Cl(g)\)
and calculate bond enthalpy of \(C-Cl\) in \(CCl_4(g)\).
\(∆_{vap}H^Θ(CCl_4) = 30.5\ kJ mol^{-1}\).
\(∆_fH^Θ(CCl_4)= –135.5\ kJ mol^{-1}\).
\(∆_aH^Θ (C)= 715.0\ kJ mol^{-1}\),    where \(∆_aH^Θ\) is enthalpy of atomisation.
\(∆_aH^Θ (Cl_2) = 242\ kJ mol^{-1}\).

For an isolated system, ∆U=0, what will be ∆S ?

For the reaction at \(298\ K\),
\(2A+B→C\)
\(∆H = 400\ kJ mol^{-1}\) and \(∆S = 0.2\ kJ K^{-1} mol^{-1}\)
At what temperature will the reaction become spontaneous considering \(∆H\) and \(∆S\) to be constant over the temperature range.

For the reaction, \(2Cl(g)→Cl_2(g)\), what are the signs of \(∆H\) and \(∆S\) ?

For the reaction
\(2A(g)+B(g)→2D(g)\)
\(∆U^Θ= -10.5\ kJ\) and \(∆S^Θ= -44.1\ JK^{-1}\).
Calculate \(∆G^Θ\) for the reaction, and predict whether the reaction may occur spontaneously.