Question

[H+] = 1.58 x 10-2 mg/L

CaCO3
[OH-] = 1.6 x 10-3 mg/L
CaCO3
is the answer but I don't know why. Can you explain why?
The {pH} of a water sample is 6.5 . Express the concentration of the hydrogen and hydroxide ions in terms of {mg} /{L}{CaCO}_{3} .

Answer 1

3.2x10^-7 mg/L

Step-by-step explanation:

pH is the negative log of the hydrogen ion concentration [H+].

A pH of 6.5 means [H+] = 3.2x10^-7 moles/liter

The molar mass of H is 1 (1 gram/mole)

A liter of solution would therefor contain 3.2x10^-7 grams of H

(3.2x10^-7 grams of H)/(1,000 grams total) = 3.2x10^-4 grams/L

Convert: (3.2x10^-4 grams/L)*(1000mg/1gram) = 3.2x10^-7 mg/L

The same process can be used for the OH concentration. But I'm confused about the role of CaCO3.