Preparation method? please help me making the solution accurate?

Question

how can i prepare0.1N of Na2S2O3 solution

Answer 1

1. In answering problems regarding preparation of solution with a given concentration, always start with the UNIT of CONCENTRATION used.

In the problem we have the NORMALITY, N.

2. Expand the Normality using the proper formula to see what is really the required in the statement. In preparation method, it usually asked about the mass of solute dissolved in a volume of the solvent.

FORMULA of NORMALITY:

(mass solute)(factor of solute)

--------------------------------------... = Normality, N

(MW of solute)(L of solution)

Arranging the equation:

(Normality)(MW)(L of solution)

--------------------------------------... = mass so solute

factor of solute

3. Evaluate the GIVEN data.

N = 0.1

MW of Na2S2O3= 157.9796

----------->For the volume of solution, there is no given data. In this case you assume 1 L of solution of 0.1 N of Na2S2O3. Assumptions are accepted in Chemistry provided you will only assume once. This assumption will serve as your basis to solve the problem.

-----------> Factor of Na2S2O3 - I think its 2 equivalence/mol but im not sure. Im not really good at determining the factor of salt compounds.

4. Substitution of data in the fomula.

(0.1eq/L)(157.9796 g/mol)(1L)

--------------------------------------... = mass of solute

2 equivelence/L

mass of solute = 7.89 grams

ANSWER: Dissolve 7.89 grams of Na2S2O3 in an enough water in a 1L Volumetric flask and dilute it into the mark of the flask.

NOTE: The process of solving is like this but Im not sure about the factor of the Na2S2O3 salt. Just check it out.