Question

The standard internal energy change for a reaction can be symbolized as Δ U ∘ rxn or Δ E ∘ rxn . For each reaction equation, calculate the energy change of the reaction at 25 ∘ C and 1.00 bar . Sn ( s ) + 2 Cl 2 ( g ) ⟶ SnCl 4 ( l ) Δ H ∘ rxn = − 511.3 kJ/mol

Answer 1

Answer : The internal energy change is, -506.3 kJ/mol

Explanation :

Formula used :

$\Delta H=\Delta U+\Delta n_gRT$

or,

$\Delta U=\Delta H-\Delta n_gRT$

where,

$\Delta H$ = change in enthalpy = $-511.3kJ/mol=-511300.0J/mol$

$\Delta U$ = change in internal energy = ?

$\Delta n_g$ = change in moles

Change in moles = Number of moles of product side - Number of moles of reactant side

According to the reaction:

Change in moles = 0 - 2 = -2 mole

That means, value of $\Delta n_gRT$ = 0

R = gas constant = 8.314 J/mol.K

T = temperature = $25^oC=273+25=298K$

Now put all the given values in the above formula, we get

$\Delta U=\Delta H-\Delta n_gRT$

$\Delta U=(-511300.0J/mol)-[-2mol\times 8.314J/mol.K\times 298K$

$\Delta U=-511300.0J/mol+4955.144J/mol$

$\Delta U=-506344.856J/mol=-506.3kJ/mol$

Therefore, the internal energy change is -506.3 kJ/mol