Question

Molten sodium chloride is used for making elemental sodium and chlorine. Suppose the electrical power to a vat containing 56.2 kg molten sodium chloride is cut off and the salt crystallizes (without changing its temperature). Calculate the enthalpy change, using data from Table 12.4.

Short answer

The enthalpy change of the system is $-2.77\times {10}^{4}kJ.$

Step-by-step solution

The given information.

The amount of sodium chloride is 56.2 kg.

Enthalpy change.

Theheat content of a specific system is termed enthalpy. The increase or decrease in enthalpy can help in deciding whether a particular reaction can take place.

The enthalpy change using the data from Table 12.4.

The value of enthalpy change from Table 12.4 is $28.8kJmol$^-1.

In this process, NaCl (l) freezes, so the q_p of the NaCl system is negative.

Therefore, the enthalpy change can be found as;

$$\begin{gathered} \Delta H=\frac{-28.8kJ}{1molNaCl}\times \frac{1molNaCl}{58.44gNaCl}\times 56.2\times {10}^{3}gNaCl \\ =-2.77\times {10}^{4}kJ \end{gathered}$$