The standard state Gibb’s free energy change for the isomerization reaction cis-2-pentene trans-2-pentene is –3.67 kJ mol–1 at 400 K. If more trans-2-pentene is added to the reaction vessel

According to Le-Chatelier's principle, when the product trans-2-pentene is added in the reaction, then the reaction is favoured in the reverse direction which results in the increase in the concentration of the reactant i.e. cis-2- pentene.