A catalyst is added to a mixture that has already reached equilibrium. What is the effect on the equilibrium position?

1. A catalyst works by lowering the activation energy of a reaction. 2. The forward and reverse reactions cross the same energy barrier, just from opposite sides. 3. Lowering that barrier therefore speeds up the forward reaction and the reverse reaction by the same factor. 4. If both rates rise equally, they stay equal to each other, so the balance point does not move. 5. The concentrations of reactants and products at equilibrium are unchanged, and so is the equilibrium constant. 6. What a catalyst does change is how quickly equilibrium is reached, which matters a great deal in industry. 7. Moving the position to the right or the left is the trap for treating a catalyst like a change of concentration or temperature. 8. A reversible reaction in a closed container never goes to completion, so the last option is wrong in principle. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 8: Chemical equilibrium_