At 100°C, pure water has a pH of 6, whereas at 25°C it has a pH of 7. This is because
A the dissociation of water is endothermic, so the concentration of hydrogen ions is lower at 100 °C than it is at 25 °C.
B the dissociation of water is exothermic, so the concentration of hydrogen ions is lower at 100°C than it is at 25°C.
C the dissociation of water is endothermic, so the concentration of hydrogen ions is higher at 100 °C than it is at 25 °C.
D at 100 °C, water has a higher concentration of hydrogen ions than of hydroxide ions.
the answer is C but how do you know that it would be C?