20. What is meant by hydration of a molecule or ion?

21. Why does ammonia increase the concentration of hydroxide ions when it is dissolved in water? What is a substance that behaves in this way called?

22. Why does hydrogen fluoride increase the concentration of hydrogen ions when dissolved in water? What is such a substance called?

23. How does the behavior of HF and LiF differ when each is dissolved in water?

24. Why is some OH- present in water even without an added base? How does this compare with the amount of H+ present in pure water?

25. What is the effect of acids and bases on litmus paper? What is such a substance called?