100 ml of an alkaline water in presence of phenolphthalein, 50 ml of the N/100 HCl. The resulting mixture in presence of methyl orange indicator consumes 35 ml of HCl. Predict the alkalinities and calculate their amounts in ppm as CaCO3 equivalent.
Question
100 ml of an alkaline water in presence of phenolphthalein, 50 ml of the N/100 HCl. The resulting mixture in presence of methyl orange indicator consumes 35 ml of HCl. Predict the alkalinities and calculate their amounts in ppm as CaCO3 equivalent.
Solution
The question is about calculating the alkalinity of water in terms of ppm as CaCO3 equivalent. Alkalinity is a measure of the capacity of water to neutralize acids. In this case, we have two types of alkalinity to consider: phenolphthalein alkalinity (P-alkalinity) and total alkalinity (T-alkalinity).
- Phenolphthalein Alkalinity (P-Alkalinity): Phenolphthalein alkalinity is determined by the amount of standard acid (HCl in this case) needed to bring the sample to a pH of 8.3. In this case, 50 ml of N/100 HCl is used.
To calculate P-Alkalinity as ppm CaCO3, use the formula: P-Alkalinity (ppm as CaCO3) = (ml of acid used * Normality of the acid * 50,000) / ml of sample
Substituting the given values: P-Alkalinity (ppm as CaCO3) = (50 ml * 1/100 * 50,000) / 100 ml = 250 ppm as CaCO3
- Total Alkalinity (T-Alkalinity): Total alkalinity is determined by the amount of standard acid needed to bring the sample to a pH of 4.5. In this case, an additional 35 ml of HCl is used (total of 85 ml of HCl).
To calculate T-Alkalinity as ppm CaCO3, use the same formula: T-Alkalinity (ppm as CaCO3) = (ml of acid used * Normality of the acid * 50,000) / ml of sample
Substituting the given values: T-Alkalinity (ppm as CaCO3) = (85 ml * 1/100 * 50,000) / 100 ml = 425 ppm as CaCO3
So, the phenolphthalein alkalinity is 250 ppm as CaCO3 and the total alkalinity is 425 ppm as CaCO3.
Similar Questions
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