List and describe the types of the types of of errors in analysis, giving exampl

Question

List and describe the types of the types of of errors in analysis, giving examples of the possible sources 2. th regards gravimetric analysis, discuss the following (a) (b) How crystal growth can be achieved. How peptization is prevented. collected the following data (triplicate analyses) towards the standardi pe 22 A t collected the manganate using sodium oxalate as a primary standard (see equation 1) 13 g of the sodium oxalate [Na(COO)2] salt was weighed off and dis followed by addition of 20-25 mL of 50% sutunc potassium 0.139water of approximately 0.13 g of the sodium about 150 mL of distilled water warming the mixture for each titration. Equa 2MnO' + 5(COO)22. + 16H' 2Mn® + 10CO2 + 8H20 The indicator blank for this titration, where permanganate was used as a specific indi 0.08 mL. Exact mass of sodium oxalate (in grams) 3 Titration number Weighing bottle +oxalate (ing) Weighing bottle (empty) (in g) 12.0723 11.9388 12.0717 11.9388 12.0745 11.9388 Titration of sodium oxalate with potassium permanganate solution (mL) Final burette reading (mL) Initial burette reading (mL) 20.95 0.32 20.25 0.12 21.02 0.25 (a) What is a primary standard? (b) Why was it necessary to warm the mixture for the sodium oxalate/permanganate t (c) Why is it important to carry out an indicator blank for the permanganate titration?

Explanation / Answer

2.2

a)

2MnO4 + 16 H+ + 5 C2O4------------à 2Mn2+ + 8H2O + 10 CO2

The substance used to prepare a standard solution is called the primary standard. Sodium oxalate is the primary standard.

b) Higher titers are obtained by increasing the temperature. So it is necessary to warm up the mixture of sodium oxalate/permanganate up to 850C.

c)

Generally the endpoint of a titration is determined using indicators. No other indicators are used to determine the endpoint, because KMnO4 acts as the indicator. Permanganate (MnO4-) ion has a dark purple color. In an acidic medium, MnO4- is reduced to colorless Mn2+ ions. On reaching the end point, the addition of the last single drop of permanganate imparts a light pink color to the solution..

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