To a 25.00-mL sample of hard water is added 5 mL of pH 10 buffer, 15...

  

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To a 25.00-mL sample of hard water is added 5 mL of pH 10 buffer, 15 drops of 0.030 M MgCl2 and 8 drops calmagite indicator. The sample is titrated with 38.55 mL of 0.0102 M EDTA to reach the endpoint. A blank solution, containing the same amount of buffer, MgCl2 and indicator, requires 1.88 mL of EDTA solution to reach the endpoint. How many moles of Ca²+ are present in the water sample? A. 3.932 10-4 B. 0.3932 C. D. E. 1.100 10-3 2.550 10-4 3.740 10-4 To a 25.00-mL sample of hard water is added 5 mL of pH 10 buffer, 15 drops of 0.030 M MgCl2 and 8 drops calmagite indicator. The sample is titrated with 38.55 mL of 0.0102 M EDTA to reach the endpoint. A blank solution, containing the same amount of buffer, MgCl2 and indicator, requires 1.88 mL of EDTA solution to reach the endpoint. How many moles of Ca²+ are present in the water sample? A. 3.932 10-4 B. 0.3932 C. D. E. 1.100 10-3 2.550 10-4 3.740 10-4