EXPERIMENT 1 STANDARDIZATION OF HCl SOLUTION WITH Na2CO3 PRIMARY STANDARD PDF

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EXPERIMENT 1 STANDARDIZATION OF HCl SOLUTION WITH Na2CO3 PRIMARY STANDARD Objective: To determine the exact molarity of a hydrochloric acid solution. Introduction : Pure sodium carbonate is a non hygroscopic primary standard reagent. A standard solution prepared by dissolving a known amount of the s...

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EXPERIMENT 1 STANDARDIZATION OF HCl SOLUTION WITH Na2CO3 PRIMARY STANDARD Objective: To determine the exact molarity of a hydrochloric acid solution. Introduction : Pure sodium carbonate is a non hygroscopic primary standard reagent. A standard solution prepared by dissolving a known amount of the solid Na2CO3 in a fixed volume can be used to standardize other acid solutions. The aim of the experiment is to prepare a standard solution of exact concentration which can later be used to standardize other solutions. HCl is not a primary standard. Thus, after a dilute HCl solution is prepared, it has to be standardized with a primary standard solution in order to determine its concentration accurately. In this experiment a standard Na2CO3 solution and a dilute HCl solution will be prepared. The HCl solution will later be standardized against the Na2CO3 solution. The reaction between HCl and Na2CO3 is as follows. 2 HCl + Na2CO3  2 NaCl + H2O + CO2

Apparatus 100 mL beaker 250 mL volumetric flask 250 mL conical flask 25 mL pipette Burette Retort stand Chemicals Na2CO3 Concentrated HCl Methyl orange indicator

Procedure (a)

(b)

(c)

Preparation of 0.05 M Na2CO3 solution 1.

Weigh accurately about 1.33 g of Na2CO3. Record the exact mass of the Na2CO3.

2.

Dissolve the Na2CO3 in about 50 mL water in a 100 mL beaker.

3.

Transfer the solution into a 250 mL volumetric flask. Rinse the beaker with distilled water.

4.

Add distilled water to the mark. Stopper the flask. Shake it by turning it upside down a few times to make the solution homogeneous.

Preparation of a dilute HCl solution 1.

Transfer about 2.2 mL of concentrated HCl into a 250 mL beaker containing a little water.

2.

Dilute the acid to approximately 250 mL with distilled water.

Standardization of the dilute HCl solution 1.

Fill a burette with the dilute HCl solution prepared in (b) above. Record the initial burette reading.

2.

Pipette 25.0 mL of the standard Na2CO3 into a 250 mL conical flask. Add 2-3 drops of methyl orange indicator.

3.

Titrate the Na2CO3 in the conical flask with the HCl from the burette slowly while shaking the flask until the indicator colour change from yellow to red. Record the burette reading at the end point of the titration.

4.

Repeat the titration 3 times. Record all your data in a table as shown in the datasheet.

5.

Calculate the exact molarity of the HCl solution.

RESULTS Your results should contain the following: 1.

Weight of Na2CO3 used

=

…………… g

2.

Standardization of HCl with Na2CO3 solution

Rough Initial burette reading (mL) Final burette reading (mL) Volume of HCl used (mL)

3.

Calculate the molarity of the HCl solution.

QUESTION Calculate the molarity of the concentrated HCl.

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