VOLUMETRIC ANALYSIS: DETERMINING THE RELATIVE MOLECULAR MASS OF A SOLUBLE BASE.

896 Words Nov 2nd, 2013 4 Pages
Objective:
To determine relative molecular mass of a soluble base, X2CO3 by carrying out an acid-base titration with the following reaction , knowing the amount of hydrochloric acid used and the amount of substance Z used.
Hypothesis:
The X in substance Z is a group 1 element because substance Z is a soluble metal carbonate and would most likely be sodium or potassium because these elements are commonly used.

Materials
100 cm3 beaker, 250 cm3 beaker, 250 cm3 volumetric flask with stopper, filter funnel, glass pipette, glass rod, de-ionized water, Substance Z, 25 cm3 bulb pipette, pipette filter, 250 cm3 conical flask, burette, burette stand & holder, 0.1225 M hydrochloric acid, methyl orange indicator.
Procedure:
Part 1:
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12. Using a bulb pipette, 25 cm3 of Substance Z was transferred into a clean conical flask.
13. A few drops of methyl orange indicator was added.
14. The substance Z solution in the conical flask was titrated with standard hydrochloric acid after the initial reading of the burette was recorded. The end-point of the titration was reached when the solution just changed from yellow to pink.
15. The final reading of the burette was recorded.
16. Steps 12 to 15 were repeated until concordant results were obtained.
17. All results were recorded in table 2.
Results
Table : Part 1, making a standard solution of substance Z
Mass of 100 cm3 beaker + Substance Z before transfer of contents (g)
61.1857
Mass of 100 cm3 beaker after transfer of contents (g)
59.5012
Mass of Substance Z used for preparing standard solution (g)
1.6845

Table : Part 2, Titration to determine the relative molecular mass of substance Z

Trial 1
Trial 2
Trial 3
Trial 4
Final reading (mL)
26.00
25.90
26.00
25.90
Initial reading (mL)
0.00
0.00
0.00
0.00
Titre (mL)
26.00
25.90
26.00
25.90
Mean titre (mL)
25.95

Burette reagent: Dilute hydrochloric acid
Conical flask reagent: Standard Substance Z
Indicator: Methyl Orange

Analysis
According to the equation below, one mole of X2CO3 reacts with two moles of HCl where X represents a Group 1 element.

1) The number of

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