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  • Publicado : 16 de diciembre de 2010
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1. What are the sources of error in this experiment?

a. The quantity of indicator used
b. An error in the reading of volume of the buret when performing the tiritation, such asparallax.
c. Incorrect weighing process in which an inaccurate amount of sample is weighed affecting the calculations performed.

2. What would happen if tap water is used instead ofdistilled water to dilute your sample?

d. Tap water is considered to have a high hardness, meaning that it contains residues of minerals which would affect the reaction during the titration process.The sample will contain residues of chlorine, calcium, magnesium. These impurities will affect the sample.

3. Why does the rate of the reaction decrease near the end point?

e. Therate of the reaction decreases because almost all available reactant (MgO) has been consumed by the EDTA meaning that the change of the solution is arriving from acidic to basic.

4. Explain whythe change from red to blue in the experiment occurs suddenly at the equivalence point instead of gradually throughout the entire titration.

f. The change from red to blue in the experimentoccurs suddenly at the equivalence point instead of gradually because the change in acidity occurs with a very little change in volume. The typical acid/base indicator exhibits its color change over arange of about 2 pH units. Therefore since the change in pH occurs suddenly within this range, the change in the indicator color will also change suddenly

5. What would happen if you add an excessof indicator?

g. For the indicator to be useful in an EDTA titration, it must bind to the metal ion less strongly than EDTA. This indicator is an organic dye that is also an acid-baseindicator. Because the color of the free indicator is pH dependent, it can be used only in certain pH ranges. If you add an excess of indicator, the change of color will be less appreciated. The...
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