Propagation of error. A mixture containing only silver nitrate and mercurous nitrate was dissolved in water and treated with excess sodium cobalticyanide, Na3[Co(CN)6] to precipitate both cobalticyanide salts:
AgNO3 FM 169.873
Ag3[Co(CN)6] FM 538.643
Hg2(NO3)2 FM 525.19
(Hg2)3[Co(CN)6]2 FM 1 633.62
(a) The unknown weighed 0.432 1 g and the product weighed 0.451 5 g. Find wt% AgNO3 in the unknown. Caution: Keep all the digits in your calculator or else serious rounding errors may occur. Do not round off until the end.
(b) Even a skilled analyst is not likely to have less than a 0.3% error in isolating the precipitate. Suppose that there is negligible error in all quantities, except the mass of product, which has an uncertainty of 0.30%. Calculate the relative uncertainty in the mass of AgNO3 in the unknown.