to determine the family member molecular mass of
* Two drops of phenolphthalein indication were added to the chloroacetic acid solution to enable all of us to determine when the solution is neutralized. Phenolphthalein is lilac in standard and neutral solutions and colorless in acidic solutions.
* When ever 20. almost eight cm3 ï 0. 1cm3 of salt hydroxide were titrated in to the flask containing 10. 00cm3 ï zero. 06 cm3 chloracetic acid solution and two drops of phenolphthalein sign, the color of the solution improved from colorless to green, which indicates that the solution have been neutralized.
Data Processing and Presentation
1 . Number of moles of sodium hydroxide reacted
Conversion factor
1 cm3 = 10-3 dm3
20. 8 cm3 = 20. 8 2. 10-3 dm3 = installment payments on your 08 2. 10-2 dm3
Number of skin moles (n) = concentration (c) * quantity (v)
= (2. ’08 * 10-2) (0. 10)
= installment payments on your 1 * 10-3 skin moles of salt hydroxide responded
2 . Number of moles of chloroacetic acid solution reacted
Chloroacetic acid (ClCH2COOH) reacts with sodium hydroxide (NaOH) to produce sodium chloroacetate (CClH2COONa) and water (H2O) according to the pursuing equation:
ClCH2COOH (aq) + NaOH (aq) ïCClH2COONa (aq) + H2O (l)
In the equation we see that:
you mole of ClCH2COOH ï 1 gopher of NaOH
x ï 2 . you * 10-3 mole NaOH
Number of skin moles of ClCH2COOH reacted sama dengan x = 1 5. 2 . one particular * 10-3 = installment payments on your 1 2. 10-3 mol
1
several. Number of skin moles of chloracetic acid in 100 cm3 chloroacetic chemical p solution
installment payments on your 1* 10-3 moles of ClCH2COOH ï 10. 00 cm3 of ClCH2COOH
x ï 100. 00 cm3 of ClCH2COOH
Number of moles of ClCH2COOH in 90. 00 cm3 solution = x = 2 . 1*10-3 * 75. 00 sama dengan 2 . you * 10-2 mol
15. 00
some. Mass of Chloroacetic acid reacted
Mass of
chloroacetic acid reacted = (mass of beaker + chloroacetic acid) ” (mass of beaker)
= (47. 80) -(45. 80)
= installment payments on your 00g
5. Experimental comparative molecular mass of chloroacetic acid
range of moles (n) = mass (m)
comparable molecular mass(Mr)
n = m (multiply by Mr)
Mr
(Mr) (n) = m (divide by n)
Mr = m = 2 . 00 = ninety five gmol-1
in 2 . you * 10-2
6. Assumptive relative molecular mass of chloroacetic chemical p
Theoretical relative molecular mass (Mr) of
chloroacetic acid solution (ClCH2COOH) sama dengan Mr Cl + 2(Mr C) +3(Mr H) +2(Mr O)
= (35. 45) + 2(12. 01) +3(1. 01) +2(16. 00)
sama dengan 94. 50 gmol-1
7. Percentage problem
Percentage problem = |theoretical value-experimental value| *100%
|theoretical value|
sama dengan |94. 40 ” ninety five | *100% = 0. 5%
| 94. 55 |
Realization and Analysis
In this test, the trial and error relative molecular mass of chloroacetic acid (ClCH2COOH) was found to be 95 gmol-1. The research was quite successful because the experimental molecular mass of chloroacetic acid is quite close to the assumptive molecular mass of chlorocetic acid (94. 50 gmol-1). This is indicated by the little percentage problem in the consequence (0. 5%). However , there were sources of error in the experiment.
Sources of mistake
1 . Man parallax error in taking volume measurements: the meniscus might not have been viewed for right aspects.
2 . Man parallax error in acquiring mass measurements: the weighing machines of the multiple beam equilibrium might not have been viewed for right angles.
3. The finish point might not have been reached. This means that a better volume and for that reason a greater number of skin moles of salt hydroxide were needed to completely neutralize the 2. 00g of chloroacetic acid. Since the reaction between chloroacetic acid and sodium hydroxide is a someone to one response, a greater number of moles of sodium hydroxide means a greater number of moles of chloroacetic acid. The relative molecular mass was found by dividing the mass of chlorocetic acid reacted over the number of moles of chloroacetic acid responded. Thus in case the number of moles of chloroacetic acid in the 2 . 00g was larger, the relative molecular mass would have recently been smaller and therefore closer to the theoretical value.
4. The beaker might not have been cleansed properly. Hence impurities might have influenced mass measurements by somewhat increasing the mass in the chloroacetic chemical p.
5. The uncertainty from the triple light beam balance (ï0. 05g) might have affected mass measurements.
6. Volume computing equipment such as the burette and pipettes might possibly not have been cleaned out and dried up properly. Impurities and traces of normal water might thus have a little bit increased volume measurements.
Improvements
1 . By using a more accurate harmony: e. g. a double beam balance.
2 . Being sure that the equipment is definitely properly cleansed before executing the experiment in order to get rid of any harmful particles.
3. Duplicating the test once or twice and taking average results. This is certainly likely to decrease the effects of unique error.
4. Making sure that the size of the multiple beam balance is looked at at right angles to reduce the possibility of parallax error occurring.
5. Being sure that the meniscus in the pipettes and burette is viewed at proper angles to reduce the possibility of parallax error developing.
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