What will cause the pH to increase and the Kwto decrease?
increasing the temperature
decreasing the temperature
adding a strong base
adding a strong acid
why is the answer B
The answer is B (decreasing the temperature).
When the temperature decreases, the equilibrium constant for the autoionization of water (Kw) will decrease. The equation for the autoionization of water is:
2H2O ⇌ H3O+ + OH-
Kw = [H3O+][OH-]
Since Kw is a constant at a specific temperature, when the temperature decreases, the value of Kw will decrease. As a result, the concentration of H3O+ (hydronium ions) and OH- (hydroxide ions) in the solution will decrease as well.
A decrease in the concentration of H3O+ and OH- ions will lead to an increase in pH. pH is a measure of the concentration of H3O+ ions in a solution. As the concentration of H3O+ ions decreases due to the decrease in temperature and subsequent decrease in Kw, the pH of the solution will increase.