List of top Chemistry Questions

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?

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 Lassaigne’s test for nitrogen in an organic compound, the Prussian blue color is obtained due to the formation of 

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

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.

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 \(0°C\).
\(C_p [H_2O(l)] = 75.3\ J mol^{–1}K^{–1}\)
\(C_p [H_2O(s)] = 36.8 \ J mol^{–1}K^{–1}\)

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

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) \(CH_3CH=CH C+H_2\)

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

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.

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

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.

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.

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?

A reaction, \(A+B→C+D+q\) is found to have a positive entropy change. The reaction will be

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

The enthalpies of all elements in their standard states are:

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

Assign oxidation numbers to the underlined elements in each of the following species: 

1. \(NaH_2\underline PO_4\) 
2. \(NaH\underline SO_4\) 
3. \(H_4\underline P_2O_7\) 
4. \(K_2\underline {Mn}O_4\) 
5. \(Ca\underline O_2\) 
6. \(Na\underline BH_4\) 
7. \(H_2\underline S_2O_7\) 
8. \(KAl(\underline SO_4)_2.12 H_2O\)

Choose the correct answer. A thermodynamic state function is a quantity

0.3780 g of an organic chloro compound gave 0.5740 g of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound.

A sample of 0.50 g of an organic compound was treated according to Kjeldahl’s method. The ammonia evolved was absorbed in 50 ml of 0.5 M H₂SO₄. The residual acid required 60 mL of 0.5 M solution of NaOH for neutralization. Find the percentage composition of nitrogen in the compound.

Explain why alkyl groups act as electron donors when attached to a \(\pi\) system.

Identify the functional groups in the following compounds.