Solutions for Na₂S₂O₃(aq) 2HCl(aq) → 2NaCl(aq) H₂O(l) SO₂(g) S(s). Which of the following would introduce the greatest increase in the rate of the chemical reaction above? An increase in temperature and decrease in the concentration of the reactant decrease in the volume and increase in the pressure of the reactant decrease in the temperature and an increase in the concentration of the reactant An increase in temperature and an increase in the concentration of the reactant Reaction rate generally increases with higher temperature (more energetic collisions) and higher concentration (more frequent collisions). Thus, the greatest increase is from both together. Correct option D.