With respect to the constituents causing alkalinity in water, which of the following situation never arises?a.CO32- and HCO3– togetherb.OH– and CO32- togetherc.OH– onlyd.HCO3– and OH– together

The situation that never arises with respect to the constituents causing alkalinity in water is c. OH– only.

Here's why:

Alkalinity in water is primarily due to the presence of bicarbonate (HCO3–), carbonate (CO32-) and hydroxide (OH–) ions.

a. CO32- and HCO3– together: This is possible because both of these ions can coexist in water, especially when the pH is between 6 and 10.

b. OH– and CO32- together: This is also possible. When the pH of water is above 10, both of these ions can be present.

c. OH– only: This situation never arises. Hydroxide ions (OH-) cannot exist alone in water because they readily react with water molecules to form either bicarbonate (HCO3-) or carbonate (CO32-) ions.

d. HCO3– and OH– together: This is possible. When the pH of water is between 8 and 10, both bicarbonate and hydroxide ions can be present.