## Determination of the Percentage Purity of a Sample of Sodium Carbonate by Back Titration

Determination of the Percentage Purity of a Sample of Sodium Carbonate by Back Titration

Name:

DATA:

Concentration of sulfuric acid ¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬ (M) 0.04588 M_______________

``Titration 1 Titration 2 Titration 3``

Final Burette Reading (mL) 24.55 mL 24.38 mL N/A
Initial Burette reading (mL) 1.10 mL 0.90 mL N/A
Volume of NaOH (mL) 23.45 mL 23.49 mL N/A

Average volume 23.47 mL__________

Sample number C15__________
Weight of sample 1.3450 g__________

``Titration 1 Titration 2 Titration 3``

Final Burette Reading (mL) 24.15 mL 22.24 mL N/A
Initial Burette reading (mL) 4.10 mL 0.20 mL N/A
Volume of NaOH (mL) 20.05 mL 20.04 mL N/A

Average volume 20.045 mL____

CALCULATIONS:

Molarity of Sodium Hydroxide

1: Calculate the number of moles of sulfuric acid in each 25.00 mL aliquot titrated.

2: Using the stoichiometry of the reaction between sulfuric acid and sodium hydroxide calculate the number of moles of sodium hydroxide required to neutralize the acid.

3:From the volume used in the titration, calculate the concentration of sodium hydroxide (mol L-1).

4: NOTE: The result you obtain should be close to the expected value (0.100 M). If it is not, check your calculation.

Percentage Purity of Sodium Carbonate

5: Calculate the total number of moles of sulfuric acid added to the carbonate. (concentration x volume)

6: Calculate the number of moles of NaOH used to titrate the unreacted sulfuric acid.

7: Using the stoichiometry of the reaction calculate the number of moles of unreacted sulfuric acid.

8: Calculate the number of moles that reacted with the carbonate and then the number of moles of carbonate itself in each 25.00 mL aliquot.

9: Use the molecular weight of Na2CO3 to determine the mass of sodium carbonate in each aliquot.

10: Determine the mass of Na2CO3 in the volumetric flask and then in your unknown sample.

11: Calculate the percentage purity of Na2CO3 in your sample from

% purity = Mass Na2CO3 X 100
Mass of sample

Qualitative Analysis for Anions

`` SO42-   CO32-   Cl-     I- ``

Ba2+ PPT – Cloudy PPT – Cloudy Clear Clear
HNO3 PPT DG N/A Yellow
Ag+ Clear Yellow Cloudy PPT – Cloudy PPT – Yellow
HNO3 N/A DG N/A N/A
NH3 N/A D D PPT
Al3+ Clear Cloudy G Clear Clear
HNO3 N/A DG N/A Light Yellow

D = Dissolves
G = Gas Evolved

What Are the Unknowns A & B and what are the steps using only the data provided in qualitative analysis for anions chart and worksheet

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