Question

17.4 mL of 0.10 M Na2S2O3 (sodium thiosulfate) was needed for titration of 25.00 mL of diluted bleach, calculate the molarity of the diluted bleach (hypochlorite ion)

The mole ratio of sodium thiosulfate to sodium hypochlorite is 2:1

Answer 1

To find the molarity of the diluted bleach, calculate the moles of Na2S2O3 used, adjust for the mole ratio to find the moles of NaOCl, and divide by the sample volume in liters. The molarity of NaOCl in the bleach is 0.0348 M.

Step-by-step explanation:

To calculate the molarity of the diluted bleach (hypochlorite ion), we use the titration data provided and the mole ratio between sodium thiosulfate and sodium hypochlorite. Since the mole ratio is 2:1, it means that two moles of Na2S2O3 are required to react with one mole of NaOCl.

Using the molarity and volume of the titrant (Na2S2O3), we first determine the number of moles of Na2S2O3 used in the reaction:

Number of moles of Na2S2O3 = Molarity × Volume (L) = 0.10 M × 0.0174 L = 0.00174 moles

Since two moles of Na2S2O3 react with one mole of NaOCl, the moles of NaOCl in the bleach sample are half:

Moles of NaOCl = 0.00174 moles / 2 = 0.00087 moles

To find the molarity of NaOCl in the 25.00 mL bleach sample, we divide the moles of NaOCl by the volume of the bleach sample in liters (0.025 L):

Molarity of NaOCl = 0.00087 moles / 0.025 L = 0.0348 M