Question

Please clearly type information no abbreviations

a) Suppose a small amount of lead(II) chloride got into your Ba(OH)2 sample before your titration, contaminating it. How do you think this contamination would affect your calculated concentration for the sample?

b) Repeat part a) only with a small amount of FeCl3 as the contaminant instead

Answer 1

If some PbCl2 is present

MW of PbCl2 = 278.1 g/mol

MW of BA(OH)2 = 171.34 g/mol

Clearly, PBCl2 is much heavier per unit mol

If we are doing gravimetry with stoichiometric relationships, then, we will have higher mass per unit mol

The concentration will be affected in that :

M = mol/V

Molarity depends on the amount of MASS and MOLAR WEIGHT of the species

then, if MW is constant for Ba(OH)2 , the mass is incorrect since we are accounting for a greater amount of ba(OH)2

b)

MW of FeCl3= 162.2 g/mol

MW of BA(OH)2 = 171.34 g/mol

As stated before,

the molar mass of FeCl3 in this case is LOWER, therefore, we are accounting for extra amount of Ba(OH)2

therefore, expect slightly higher Concentration