Question

In an alkalinity titration of a 100.0 ml sample of water from a hot spring, 2.56 ml of a 0.0325 m solution of hcl is needed to reach the first equivalence point (ph = 8.3) and another 10.42 ml is needed to reach the second equivalence point (ph = 4.0). if the alkalinity of the spring water is due only to the presence of carbonate and bicarbonate, what are the concentrations of each of them?

Answer 1

The concentration of bicarbonate (HCO3^-) is 0.000832 M and that of carbonate (CO3^2-) is 0.003386 M in the hot spring water, determined through titration analysis.

Step-by-step explanation:

To determine the concentrations of carbonate (CO3^2-) and bicarbonate (HCO3^-) in the hot spring water, we use the titration data provided. At the first equivalence point reached with 2.56 mL of 0.0325 M HCl, we have neutralized the bicarbonate present in the 100.0 mL water sample. To find the bicarbonate concentration, use the following:

Bicarbonate molarity = (Moles of HCl) / (Volume of water sample in liters)

= (2.56 mL * 0.0325 M) / 0.100L
= 0.0832 mmol / 0.100 L
= 0.000832 M

Next, to determine the carbonate concentration, we consider the amount of HCl needed to reach the second equivalence point:

Total HCl used = 2.56 mL + 10.42 mL = 12.98 mL
Carbonate molarity = (Moles of HCl for carbonate) / (Volume of water sample in liters)

= ((12.98 mL - 2.56 mL) * 0.0325 M) / 0.100 L
= 0.3386 mmol / 0.100 L
= 0.003386 M

Hence, the concentrations of bicarbonate and carbonate in the hot spring water are 0.000832 M and 0.003386 M, respectively.