Question

Gravimetric Analysis of a Chloride Salt QUESTIONS 1. The following percentages of chloride were found: 32.52%, 32.14%, 32.61%, and 32.75% (a) Find the mount, the standard deviation, and the relative standard deviation (b) Can any result be discarded? 2. Barium can be analyzed by precipitating it as BaSO, and determining the mass of the precipitate. When a 0.269 g sample of a barium compound was treated with excess H,SO, 0.0891 g of BaSo, formed. What percentage of barium is in the compound? 3. What percentage of sodium is in pure table salt? 4. How many milligrams of sodium are contained in 4.50 g of NaCl? 5. An impure sample of table salt that weighed 0,8421 g when dissolved in water and treated with excess AgNO, formed 2.044 g of AgCl. What percentage of NaCl is in the impure sample? 6. List at least three sources of error in this experiment.

Answer 1

SOLN 1

Mean = $\frac {\sum x_i}{n}$

hence

Count, N: 4 Sum, Ex: 130.02 Mean, X 32.505 Variance, s2 0.068166666666667 Steps s = n (ti – T)? 92 = E(X;- ? N-1 - (32.52 -32.505)2 + + (32.75 -32.505)2 -0.2045 4-1 = 0.068166666666667 S = 10.068166666666667 = 0.26108746937888

RSD = s/ x = 0.26 / 32.505 = 0.8 or 80%

(b) For this data set RSD have as suh no physical signfiance hence can be discarded

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