Monday, January 30, 2012

STPM - Experiment 5

Experiment 5

Title: Volumetric Analysis – stoichiometry

Purpose: To determine the exact concentration of a monobasic acid, HX (KA1)

Materials and apparatus:
1.     Volumetric flask and stopper (250cm3)
2.     Electric balance ±0.01 g
3.     Pipette and pipette filler (25cm3)
4.     Volumetric flask and stopper (100cm3)
5.     Burettes (50cm3)
6.     Retort stand and clamp
7.     White tile
8.     Wash  bottle filled with distilled water
9.     Spatula
10.                        Titration flasks
11.                        Glass rod
12.                        Filter funnel
13.                        Beaker (80cm3)
14.                        Beaker (250cm3)
15.                        KA1 (monobasic acid, HX)
16.                        Methyl orange as indicator
17.                        Solid sodium carbonate
18.                        Distilled water

To determine the exact concentration of a monobasic acid, HX,a standard base solution is prepared. Then, a certain amount of standard base solution is titrated with the monobasic acid. This is an acid-base titration. The equation for the reaction is
 Na2CO3(aq) + 2HX(aq) → 2NaX(aq) + H2O(l) + CO2(g)

1.     Weight accurately about 13.20-13.50g of solid sodium carbonate in a small beaker. Dissolve this in the beaker. Transfer the solution and washing into a 250cm3 standard flask and make up to the mark with distilled water. Shake well.
2.     Pipette 25.0 cm3 of the standard solution of sodium carbonate into a conical flask. Add two or three drops of methyl orange indicator and titre this solution with KA1. Readings are recorded in the table. The titration is repeated three times to achieve accurate results.

Titration number
Final reading/cm3

Initial reading/cm3

Volume of KA1/cm3

Mass of beaker + sodium carbonate= _________________
Mass of empty beaker                       = _________________
Mass of sodium carbonate               = _________________

1.     25.0 cm3 of standard solution of sodium carbonate required __________ of KA1 for complete reaction.
2.     Average titre value =
3.     Calculate the concentration of sodium carbonate.
4.     Calculate the concentration of the monobasic acid, HX in KA1.


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