1.1. At 298K, water molecules dissociate into equal quantities of ions, and the pH is 7. 

i) Write an equation to show the dissociation of water. 

ii) At 313 K, the pH of water is 6.77. Explain why water is neutral at a pH of 6.77 at this temperature.

1.2. The ionic product of water, K_w, can be used to find the pH of a strong base. Changing the temperature will affect the value for K_w.

i) Give the expression and units for the ionic product of water, K_w.

ii) As temperature is increased, the value for K_w  also increases. Explain why.

1.3. At 40 ℃, the K_w of pure water is 2.916 x 10^-14 mol² dm^-6. 

Calculate the pH of pure water. Give your answer to 3 significant figures.

1.4. Strong bases fully ionise in water, as shown by the equation of dissociation of sodium hydroxide:

NaOH (aq) →  Na⁺ (aq) + OH^- (aq)

At 298K, K_w is 1 x 10^-14 mol² dm^-6. 

Calculate the pH of a 0.05 mol dm^-3 solution of NaOH at 298 K. Give your answer to 3 significant figures.        

1.5. The ionic product of water, K_w is an equilibrium constant.

However, the expression for K_w does not include the concentration of water. Explain why.