Question

A sample of river water at 20°C is analyzed and the following parameters are found

for it:
Phenolphthalein alkalinity = 5.8 x10-6 M, Total alkalinity = 2.8 × 10-5 M; pH = 8.5
Hardness 10.0 mg CaCO3/L; [Mg2+] = 3.8 x 105 M
Calculate the concentrations of [Ca²+], [CO32] and [HCO3] in this water sample.

Please explain in detail

Answer 1

The concentrations of [Ca²+], [CO32-], and [HCO3-] in the water sample can be calculated based on the given parameters and chemical reactions.

Step-by-step explanation:

The concentrations of [Ca²+], [CO32-], and [HCO3-] in the water sample can be calculated based on the given parameters and chemical reactions.

First, we need to determine the concentration of [Ca²+]. Since the water sample has a hardness of 10.0 mg CaCO3/L, we can convert this to molar concentration using the molar mass of CaCO3. [Ca²+] = 10.0 mg/L ÷ molar mass of CaCO3.

Next, we can calculate the concentration of [CO32-]. From the reaction CaCO3 + H2CO3 → Ca²+ + 2HCO3-, we know that the concentration of [CO32-] is twice the concentration of [Ca²+]. [CO32-] = 2 × [Ca²+].

Lastly, we can calculate the concentration of [HCO3-]. From the reaction CaCO3 + H2CO3 → Ca²+ + 2HCO3-, we know that the concentration of [HCO3-] is twice the concentration of [Ca²+]. [HCO3-] = 2 × [Ca²+].