The ionization enthalpy of $\mathrm{Na}^{+}$ formation from $\mathrm{Na}_{(\mathrm{g})}$ is $495.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$, while the electron gain enthalpy of Br is $-325.0 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Given the lattice enthalpy of NaBr is $-728.4 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The energy for the formation of NaBr ionic solid is (-) _____ $\times 10^{-1} \mathrm{~kJ} \mathrm{~mol}^{-1}$.

JEE Main · 2021 · 25 Feb 2021 · Shift 1 · Chemical Thermodynamics

The ionization enthalpy of

Na^{+}

formation from

Na_{(g)}

495.8 kJ mol^{- 1}

, while the electron gain enthalpy of Br is

- 325.0 kJ mol^{- 1}

. Given the lattice enthalpy of NaBr is

- 728.4 kJ mol^{- 1}

. The energy for the formation of NaBr ionic solid is (-) _____

\times 1 0^{- 1} kJ mol^{- 1}

Answer: 5576

Solution

Building the solid from gaseous sodium and bromine atoms takes three steps: the sodium atom is ionised, the bromine atom takes up that electron, and the ions come together in the lattice. Adding the three energies,

Δ H = 495.8 + (- 325.0) + (- 728.4) = - 557.6 kJ mo l^{- 1}

Written in the units asked for,

- 557.6 = - 5576 \times 1 0^{- 1} kJ mo l^{- 1}

, so the required figure is 5576.

JEE Main · 2021 · 25 Feb 2021 · Shift 1 · Integer answer

Practise more: all JEE Main PYQs on Chemical Thermodynamics →

More JEE Main questions on Chemical Thermodynamics

Which of the following graphs between pressure 'P' versus volume 'V' represent the maximum work done?
JEE Main 2026View solution →
For the reaction, $N_{2} O_{4} ⇌ 2 NO_{2}$ , graph is plotted as shown below. Identify correct statements.

A. Standard free energy change for the reaction is $- 5.40 kJ mol^{- 1}$ .
B. As $Δ G^{⊖}$ in graph i …
JEE Main 2026View solution →
Use the following data:
Substance $\frac{Δ _{f} H ^{⊖} ( 500 K )}{kJ mol ^{- 1}}$ $\frac{S ^{⊖} ( 500 K )}{J K ^{- 1} mol ^{- 1}}$
| …
JEE Main 2026View solution →
Dissociation of a gas $A_{2}$ takes place according to the following chemical reactions. At equilibrium, the total pressure is 1 bar at 300 K.
$A_{2} (g) ⇌ 2 A (g)$
The standard Gibbs energy of formation of the involv …
JEE Main 2026View solution →
Consider the following data:
$Δ_{f} H^{Θ}$ (methane, g) $= - X kJ mol^{- 1}$
Enthalpy of sublimation of graphite $= Y kJ mol^{- 1}$
Dissociation enthalpy of …
JEE Main 2026View solution →
If the enthalpy of sublimation of Li is $155 kJ mol^{- 1}$ , enthalpy of dissociation of $F_{2}$ is $150 kJ mol^{- 1}$ , ionization enthalpy of Li is $520 kJ mol^{- 1}$ , electron gain enthalpy of F is $- 313 kJ mol^{- 1}$ , standard enthalpy o …
JEE Main 2026View solution →