Tap water at room temperature has a ph of 7.2 and carbonate alkalinity of 200 mg/l (= 40 mmol/l). what is the concentration of bicarbonate and carbonate in mol/l?

the concentration of bicarbonate is [HCO₃⁻] = 0,03996 M and carbonate is [CO₃²⁻] = 3,56x10⁻⁵ M.

Explanation:

Carbonate-bicarbonate is:

HCO₃⁻ ⇄ CO₃²⁻ + H⁺ With pka = 10,25

Using Henderson-Hasselbalach formula:

pH = pka + log₁₀

7,2 = 10,25 + log₁₀

8,91x10⁻⁴ = (1)

Also:

0,040 M = [CO₃²⁻] + [HCO₃⁻] (2)

Replacing (2) in 1:

[HCO₃⁻] = 0,03996 M

Thus:

[CO₃²⁻] = 3,56x10⁻⁵ M

I hope it helps.

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the correct answer would be d. hope this !