The steps for determining the concentration of a sample of hydrochloric acid are listed below : Step (1): A 0.1038 M standard sodium carbonate solution was prepared by dissolving 2.750 g of anhydrous sodium carbonate solid in deionised water and made up to 250.0 cm3 .Step (2): 25.0 cm' of the standard solution obtained in Step (1) was transferred to a clean conical flask andthen a few drops of methyl orange were added. Step (3): The sample of hydrochloric acid was put into a burette. The standard solution in the conicalflask was titrated with the hydrochloric acid. Step (2) and Step (3) were repeated for several times. The table below shows the results of the titrations: Trial I 2 3 4 Final burette reading/ cm3 30.85 28.75 28.30 31.35 27.25 Initial burette reading/ cm3 2.00 1.50 1.00 3.00 0.00 (a) Describe the procedure in preparing the standard sodium carbonate solution in Step (I). (b) State the colour change at the end point of the titration. (c) Calculate a reasonable average for the volume of the hydrochloric acid used in the titrations (d) Calculate the concentration of hydrochloric acid (in moldm- 3) in the sample. (Relative atomic masses : H = 1.0, Cl = 35.5)
The steps for determining the concentration of a sample of hydrochloric acid are listed below :
Step (1): A 0.1038 M standard sodium carbonate solution was prepared by dissolving 2.750 g of
anhydrous sodium carbonate solid in deionised water and made up to 250.0 cm3
.Step (2): 25.0 cm' of the standard solution obtained in Step (1) was transferred to a clean conical flask andthen a few drops of methyl orange were added.
Step (3): The sample of hydrochloric acid was put into a burette. The standard solution in the conicalflask was titrated with the hydrochloric acid.
Step (2) and Step (3) were repeated for several times. The table below shows the results of the titrations:
Trial
I
2
3
4
Final burette reading/ cm3
30.85
28.75
28.30
31.35
27.25
Initial burette reading/ cm3
2.00
1.50
1.00
3.00
0.00
(a) Describe the procedure in preparing the standard sodium carbonate solution in Step (I).
(b) State the colour change at the end point of the titration.
(c) Calculate a reasonable average for the volume of the hydrochloric acid used in the titrations
(d) Calculate the concentration of hydrochloric acid (in moldm- 3) in the sample.
(Relative
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