pKw =14 at 25 °C, the pKw at 100 °C is

Explanation

The ionization constant of water (Kw) increases as temperature increases, which means more water molecules ionize into hydrogen and hydroxide ions at higher temperatures. Since pKw is the negative logarithm of Kw, an increase in Kw results in a decrease in pKw. At 25 °C, pKw is 14, but at 100 °C, it is less than 14. Thus, the correct answer is pKw < 14. The other options suggest either no change or incorrect changes in the ionization of water with temperature, which do not align with the known behavior of water.