Determination of Na2CO3 in washing soda

Determination of Na2CO3 in washing soda concerns the technique of titrimetric analysis.

Theory

Sodium carbonate (Na₂CO₃) content in washing soda (Na₂CO₃.10H₂O) solution can be determined by titrimetric method. The alkali carbonate (CO₃^2-) of the solution can be titrated with a standard acid solution. A standard HCl solution will be used for this purpose.

Na₂CO₃ + 2HCl = 2NaCl + CO₂ + H₂O

Apparatus

There are various apparatuses during the determination of Na₂CO₃ in washing soda. These apparatus are conical flask, pipette, burette, beaker, funnel, volumetric flask, and electric balance.

Reagents and chemical

There are various reagents and chemicals during the determination of Na₂CO₃ in washing soda that are hydrochloric acid and washing soda.

Indicator

Methyl orange

Procedure for the determination of Na2CO3 in washing soda

Step-1: standardization of HCl with standard Na₂CO₃ solution

Preparation of standard 0.1M 100 ml Na₂CO₃ solutions: Prepare 100 ml of 0.1M Na₂CO₃ solution by dissolving the calculated amount of anhydrous sodium carbonate in 100 ml distilled water in a volumetric flask.

Standardization of supplied HCl solution: Take 10 ml of the prepared 0.1M Na₂CO₃ solution in a conical flask, Add 2 drops of the methyl orange indicator, and note the color of the solution. Now, titrate by adding HCl dropwise from the burette into the solution. This titration must continue until the solution becomes a faint yellow and then wash the conical flask by spraying a little distilled water from the wash bottle. Find the volume of consumed acid from initial and final readings. Perform three times titrations calculate the volume of consumed acid and note them in your lab book.

Step 2: Titration of washing soda solution with HCl

First, take 10 ml washing soda solution with a pipette in a 250 ml conical flask. Then add 1 drop methyl orange indicator to this solution. Titrate the solution with standard HCl solution until the color changes to orange from yellow. Perform three times titrations calculate the volume of consumed HCl and note them in your lab book.

Data Table for the determination of Na2CO3 in washing soda

Table 1:  Titration of Hydrochloric Acid against Standard Sodium Carbonate Solution

[N.B.= The following values can be changed based on your sample content]

Observation Number	Volume of Na2CO3 (ml)	Initial burette reading (ml)	Final burette reading (ml)	Volume consumed HCl (ml)	Average volume of Consumed HCl (ml)
1	10	40	25	15
2	10	25	9.8	15.2	15.167
3	10	40	24.6	15.3

Table 2: Titration of Washing soda by HCl

[N.B.= The following values can be changed based on your sample content]

Observation Number	Volume of Na2CO3.10H2O (ml)	Initial burette reading (ml)	Final burette reading (ml)	Volume of consumed HCl (ml)	Average volume of HCl (ml)
1	10	40	31.3	8.7
2	10	31.3	22.8	8.5	8.533
3	10	22.8	14.4	8.4

The calculation for the determination of Na2CO3 in washing soda

Step-1: Standardization of HCl with standard Na₂CO₃ solution calculation

From the balanced neutralization reaction between HCl with standard Na₂CO₃ solution, we get the following:

1 mole Na₂CO₃ = 2 moles HCl

We apply the following formula,

(V_Na2CO3 x M _Na2CO3 )/ (V_HCl x M_HCl)= ½

Or, M_HCl = (2 x V_Na2CO3 x M _Na2CO3 )/ V_HCl

Or, M_HCl = ( 2 x 10 x 0.1)/ 15.167

Or, M_HCl = 0.1318 M

Step 2: Determination of sodium carbonate in washing soda calculation

From the balanced neutralization reaction equation,

2 moles of HCl= 1 mole of Na₂CO₃

Or, 1 mole of HCl= ½ mole of Na₂CO₃

Or, 1000ml 1M HCl=½ x 106 gm of Na₂CO₃

Or, 1ml 1M HCl = {(106 x 8.5 x 0.1318) / (2 x 1000)}

                       =0.0593 gm of Na₂CO₃

If the 500 ml tested solution is made from 4gm washing soda, then we will calculate the following way,

10 ml Na₂CO₃.10H₂O contain= 0.0593 gm of Na₂CO₃

500 ml Na₂CO₃.10H₂O contain= (0.0593×500)/10

                                                  =2.968 gm of Na₂CO₃

4gm washing soda (Na₂CO₃.10H₂O) contain 2.968 gm of Na₂CO₃

100gm washing soda (Na₂CO₃.10H₂O) contain= (2.968 x 100) /4

                                                                    =74.219%

Result: The percentage of the Na₂CO₃ in washing soda (Na₂CO₃.10H₂O) = 74.219%

Important questions for Viva-voce related to the determination of Na2CO3 in washing soda

What is titration?

Titration is one type of chemical qualitative analysis technique that is used to determine the concentration of an unknown solution.

What is analyte titrate or titrand?

The analyte or titrate or titrand refers to the substance whose concentration is unknown and the concentration can be determined by reacting it with titrant after adding a suitable indicator.

What is titrant?

A titrant is one type of solution whose concentration is known that is being added to the titrate solution to determine its concentration.   

What is an indicator in chemistry?

Indicators in chemistry are weak acids or bases and the solution of indicators changes color due to changes in pH.

What is washing soda in chemistry?

Washing soda is a common chemical substance with the formula Na₂CO₃.10H₂O, also known as sodium carbonate with water crystal, and it’s a salt of carbonic acid.

What are the uses of washing soda?

Washing soda is used to remove stains, unclog drains, and greasy build-up in pots and pans, clean outdoor furniture, clean the washing machine, etc.

What is the chemical name of washing soda?

The washing soda’s chemical name is sodium carbonate decahydrate.

Is washing soda toxic?

Washing soda is usually not very toxic in small amounts but it creates long-term effects, even death if it is into the human body in large amounts.

What is the chemical formula of washing soda?

The washing soda chemical formula is Na₂CO₃.10H₂O.