13. Solving a chemistry problem

3. Calculate how much of the initial substance is required to be taken to prepare a given volume of an acid or base solution with a given concentration. Write down the calculation formulas and bring all the required calculations.
Indicate the adjusting substance, the primary standard, write down the equations of reactions occurring in the solution during standardization, and give formulas for calculating the exact concentration of the prepared solution.
The variant number is determined by the last digit of the cipher.
Starting material Concentration of stock solution Volume, ml Concentration
Na2S2O3 fixanal
0.1 mol/l 200 С(Na2S2O3)=0.0500 mol/l.