Final answer:
To find the pH of pure water at 40.0°C using the ionization constant (Kw), calculate the concentration of hydrogen ions and use the formula pH = -log [H3O+]. The calculation results in pH ≈6.8, which rounds to 6.00 as the closest choice provided.
Step-by-step explanation:
To calculate the pH of pure water at 40.0°C with a given ionization constant for water (Kw) of 2.92×10-14, we need to understand that in pure water, the concentration of hydrogen ions ([H3O+]) equals the concentration of hydroxide ions ([OH-]).
Since Kw = [H3O+]*[OH-], we can solve for the concentrations of [H3O+] and [OH-], which will be equal and can be found by taking the square root of Kw. Therefore, [H3O+] = [OH-] = √(2.92×10-14) = 1.71×10-7M.
To find the pH, we use the formula pH = -log [H3O+], which gives us pH = -log(1.71×10-7) = 6.77. However, the answer must be rounded to a single decimal place or a whole number as per the options provided. So, the pH is approximately 6.8, which is not an option here. Thus, the closest correct answer from the provided choices would be A. 6.00.