List of top Chemistry Questions on Enthalpy change asked in JEE Main

Given below are two statements:
Statement (I): The radius of isoelectronic species increases in the order: \[ \text{Mg}^{2+} < \text{Na}^{+} < \text{F}^{-} < \text{O}^{2-} \] Statement (II): The magnitude of electron gain enthalpy of halogens decreases in the order: \[ \text{Cl} > \text{F} > \text{Br} > \text{I} \] In light of the above statements, choose the most appropriate answer from the options given below:

The incorrect relationship in the following pairs in relation to ionisation enthalpies is:

The group 14 elements A and B have the first ionisation enthalpy values of 708 and 715 kJ mol$^{-1}$ respectively. The above values are lowest among their group members. The nature of their ions A$^{2+}$ and B$^{4+}$ respectively is:

Consider the following cases of standard enthalpy of reaction ($ \Delta H_f^\circ $ in kJ mol$^{-1}$): \[ \text{C}_2\text{H}_6(g) + 7 \text{O}_2(g) \rightarrow 2 \text{CO}_2(g) + 3 \text{H}_2\text{O}(l) \quad \Delta H_1^\circ = -1550 \] \[ \text{C(graphite)} + \text{O}_2(g) \rightarrow \text{CO}_2(g) \quad \Delta H_2^\circ = -393.5 \] \[ \text{H}_2(g) + \frac{1}{2} \text{O}_2(g) \rightarrow \text{H}_2\text{O}(g) \quad \Delta H_3^\circ = -286 \] The magnitude of $ \Delta H_f^\circ $ of $ \text{C}_2\text{H}_6(g) $ is $\_\_\_\_\_$ kJ mol$^{-1}$ (Nearest integer).

$\text{Standard enthalpy of vaporisation for CCl}_4 \text{ is 30.5 kJ mol}^{-1}. \text{ Heat required for vaporisation of } 284 \, \text{g of CCl}_4 \text{ at constant temperature is } \_\_\_\_ \, \text{kJ.} \\ \text{(Given molar mass in g mol}^{-1}\text{; C = 12, Cl = 35.5)}$

$\Delta_{vap}H^\circ$ for water is $+40.49 \, \text{kJ mol}^{-1}$ at 1 bar and $100^\circ\text{C}$. Change in internal energy for this vaporisation under same condition is .............. kJ mol$^{-1}$. (Integer answer)
(Given R = 8.3 J K$^{-1}$ mol$^{-1}$)

$\text{Two reactions are given below:}$ \[ 2\text{Fe}_{(s)} + \frac{3}{2}\text{O}_{2(g)} \rightarrow \text{Fe}_2\text{O}_{3(s)}, \Delta H^\circ = -822 \, \text{kJ/mol} \] \[ \text{C}_{(s)} + \frac{1}{2}\text{O}_{2(g)} \rightarrow \text{CO}_{(g)}, \Delta H^\circ = -110 \, \text{kJ/mol} \] $\text{Then enthalpy change for the following reaction}$ \[ 3\text{C}_{(s)} + \text{Fe}_2\text{O}_{3(s)} \rightarrow 2\text{Fe}_{(s)} + 3\text{CO}_{(g)} \]

An ideal gas undergoes a cyclic transformation starting from the point $ A $ and coming back to the same point by tracing the path $ A \to B \to C \to A $ as shown in the diagram. The total work done in the process is $ \_\_\_\_ $ J.

A transition metal 'M' among Sc, Ti, V , Cr, Mn and Fe has the highest second ionisation enthalpy. The spin only magnetic moment value of M+
ion is ______ BM (Near integer) (Given atomic number Sc : 21, Ti : 22, V : 23, Cr : 24, Mn : 25, Fe : 26)

When equal volume of 1M HCl and 1M H$_2$SO$_4$ are separately neutralized by excess volume of 1M NaOH solution, X and Y kJ of heat is liberated respectively. The value of Y/X is ____.

Decreasing order of electron gain enthalpy of the following elements (magnitude only)
Sulphur A, Bromine - B, Fluorine C, Argon D

If standard enthalpy of vaporization of $CCl_4$ is $30.5$ kJ/mol, find heat absorbed for vaporization of $294 $ gm of $CCl_4$. [Nearest integer] [in kJ/mol]

At $25^{\circ} C$, the enthalpy of the following processes are given:
$H _2( g )+ O _2( g ) \rightarrow 2 OH ( g ) \Delta H ^{\circ} =78 \,kJ \,mol ^{-1}$
$H _2( g )+1 / 2 O _2( g ) \rightarrow H _2 O ( g ) \Delta H ^{\circ} =-242 \,kJ \,mol ^{-1}$
$H _2( g ) \rightarrow 2 H ( g ) \Delta H ^{\circ} =436\, kJ \,mol ^{-1}$
$1 / 2 O _2( g ) \rightarrow O ( g ) \Delta H ^{\circ} =249\, kJ\, mol ^{-1}$
What would be the value of $X$ for the following reaction?______ (Nearest integer)
$H _2 O ( g ) \rightarrow H ( g )+ OH ( g ) \Delta H ^{\circ}= X\, kJ\, mol -1$

Enthalpies of formation of $CCl _4( g ), H _2 O ( g ), CO _2( g )$ and $HCl ( g )$ are $-105,-242,-394$ and $-92\, kJ$ mol $^{-1}$ respectively The magnitude of enthalpy of the reaction given below is ___$kJ \, mol ^{-1}$ (nearest integer) $CCl _4( g )+2 H _2 O ( g ) \rightarrow CO _2( g )+4 HCl ( g )$

The difference between electron gain enthalpies will be maximum between

The correct order of hydration enthalpies is
(A) K⁺
(B) Rb²⁺
(C) Mg²⁺
(D) Cs⁺
(E) Ca²⁺
Choose the correct answer from the options given below:

At 25°C and 1 atm pressure, the enthalpy of combustion of benzene (I) and acetylene (g) are –3268 kJ mol^–1 and –1300 kJ mol^–1, respectively. The change in enthalpy for the reaction 3C₂H₂(g) → C₆H₆(I), is

The enthalpy of combustion of propane, graphite and dihydrogen at 298 K are –2220.0 kJ mol^–1, –393.5 kJ mol^–1 and –285.8 kJ mol^–1, respectively.The magnitude of enthalpy of formation of propane (C₃H₈) is _____ kJ mol^–1. (Nearest integer)

At 25°C and 1 atm pressure,the enthalpies of combustion are as given below:

$Substance$	$H_2$	$C(graphite)$	$C_2H_6(g)$
$\frac{D_cH^{\theta}}{kJmol^{-1}}$	$-286.0$	$-394.0$	-1560.0

The enthalpy of formation of ethane is

Which of the following 3d-metal ion will give the lowest enthalpy of hydration (Δ_hydH) when dissolved in water?

2.4 g coal is burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atm pressure. The temperature of the calorimeter rises from 298 K to 300 K. The enthalpy change during the combustion of coal is –x kJ mol^–1. The value of x is ______.(Nearest integer)
(Given : Heat capacity of bomb calorimeter is 20.0 kJ K^–1. Assume coal to be pure carbon)

The enthalpy of combustion of propane, graphite and dihydrogen at 298 K are –2220.0 kJ mol^–1, –393.5 kJ mol^–1 and –285.8 kJ mol^–1, respectively. The magnitude of enthalpy of formation of propane (C₃H₈) is _____ kJ mol^–1. (Nearest integer)

The first ionization enthalpy of Na, Mg and Si, respectively, are : 496, 737 and 786 kJ mol^–1. The first ionization enthalpy (kJ mol^–1) of Al is:

An element A of group1 shows similarity to an element B belonging to group 2. If A has maximum hydration enthalpy in group 1 then B is:

17.0 g of NH₃ completely vapourises at – 33.42°C and 1 bar pressure and the enthalpy change in the process is 23.4 kJ mol^–1. The enthalpy change for the vapourisation of 85 g of NH₃under the same conditions is ____ kJ.