Question

A student followed the procedure of this experiment to determine the percent NaOCl in a commercial bleaching solution that was found in the basement of an abandoned house. The student diluted 50.00mL of commercial bleaching solution to 250mL in a volumetric flask, and titrated a 20-mL aliquot of the diluted bleaching solution. The titration required 35.46mL of 0.1052M Na2S2O3 solution. A faded price label on the gallon bottle read $0.79. The density of the bleaching solution was 1.10g/mL.

Calculate the number of moles of S2O3^2- ion required for the titration.

Answer #1

his reaction must be carried out in a basic solution - It is
necessary to add NaOH to the solution before titration.

Equation:

4 NaOCl + Na2S2O3 + 2 NaOH → 4 NaCl + 2 Na2SO4 + H2O

4mol NaOCl react with 1 mol Na2S2O3

Calculate the number of mol Na2S2O3:

Mol Na2S2O3 in 35.46mL of 0.152M solution = 35.46/1000*0.152 =
**0.00539 mol Na2S2O3** used in the
titration.

1) How many mol of NaOCl is in the 20mL titration sample:

From the balanced equation: 4* 0.00539 = 0.0216 mol NaOCl in
20mL

2) mol NaOCl in the 250mL of solution = 250/20* 0.0216 = 0.269 mol
NaOCl

3) Therefore 50mL of the original commercial bleaching solution
contains 0.269 mol NaOCl

4) Calculate mol NaOCl in 1 litre of original commercial solution =
1000/50*0.269 = 5.38 mol NaOCl

5) molar mass NaOCl = 23+35.5+16 = 74.5g/mol.

5.38mol = 5.38*74.5 = 400.81 g NaOCl in 1 litre of solution.

A student followed the procedure in Part I to determine the mass
of an unknown acid that would require 30.00 mL of 0.123 M sodium
hydroxide. The student found that 8.761 mL sodium hydroxide
solution was needed to titrate a 0.0526 g sample of acid to the
equivalence point. Calculate the mass (in grams) of unknown
required for a 30.00 mL titration.

A student followed the procedure of this experiment to determine
the Ksp of zinc(II) iodate, Zn(IO3)2. Solutions of Zn(NO3)2 of
known concentrations were titrated with 0.200 M KIO3 solutions to
the first appearance of a white precipitate. For each of the
zinc(II) nitrate solution concentrations below, calculate the
expected concentration of iodate that would be required to initiate
precipitation of zinc(II) iodate. Show all calculations. (Assume
that Ksp = 3.9 x 10-6 at 25oC for zinc(II) iodate). a) 0.100 M...

Assuming you weighed out a 2.3684 g
sample of your unknown, and dissolved and diluted it as in the
procedure below, and it took 35.63 mL of a 0.1025 M HCl titrant to
reach the endpoint, what are the weight percents of
Na2CO3 and NaHCO3 in your unknown
sample?
Hints:
-Set g Na2CO3 =
X
-Eqn A: bicarbonate + carbonate = diluted weighted mass
(remember, the mass is not 2.3684, you diluted it
before you titrated it.Calculate the diluted g...

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