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Figure 5.1 :- - Table 5.1 :- Please show calculations. A, B, C, D 6) Note: Calcu

ID: 891034 • Letter: F

Question

Figure 5.1 :-

-

Table 5.1 :-

Please show calculations. A, B, C, D

6) Note: Calculations must be explicitly shown throughout You are getting ready to analyze a 50-mL sample, add a few drops of phenolphthalein indicator and the sample turns from colorless to magenta. a) This is an indication that the sample has what type of alkalinity? b) Assume that the initial volume of titrant in the burette reads 3.0 mL when you start to titrate the sample. At the moment that the indicator in the sample changes color from magenta to colorless the burette reads 8.0 mL. You then add a few drops of methyl orange indicator and the sample changes color from colorless to pale orange. You continue the titration until the indicator in the sample changes color from pale orange to salmon-color, and that this point the volume of titrant in the burette reads 12.0 mL. Looking at Figure 5.1 (page 24 in the Manual), what volumes of titrant represent "P and "T" alkalinity in this case? P-alkalinity = T-alkalinity = mL mL

Explanation / Answer

part A) When a solution of 50 ml is being analyzed and then the addition of few drops of phenolpthalein indication is made the sample turns magenta from colourless. This is an indication of carbonate alklanity

part B)   P alklanity is the hydroxyl and half of the carbonate alklanity.

specimen calculation

volume of H2SO4 = 5 ml

Normality of H2SO4 = 0.02 N

volume of sample = 50 ml

equivalent weight of CaCO3 = 1000

P alklanity = Volume of H2SO4 X Normality X 50 X 1000 / volume of sample

= 5.0 x 0.02 x 50 x 1000 /100 = 50 mg/ml as CaCO3 equivalent

T alklanity

specimen calculation

volume of H2SO4 = 9 ml

Normality of H2SO4 = 0.02 N

volume of sample = 50 ml

equivalent weight of CaCO3 = 1000

T alklanity = Volume of H2SO4 X Normality X 50 X 1000 / volume of sample

9.0 x 0.02 x 50 x 1000 /100 = 90 mg/ml as CaCO3 equivalent

interpretation of results

P<1/2 T

valueS of P and T oH - CO3 2- HCO3- P=0 0 0 T= 90

P<1/2 T

0 2P= 100 T - 2P = -10 P=1/2 T 0 2P = 100 0 P<1/2 T 2 (P-T) = -80 2 (T-P) = 80 0 P=T P = 50 0 0
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