Pre-Laboratory Assignment 1. Read in TECH 316, Filtration, in this series or in
ID: 541547 • Letter: P
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Pre-Laboratory Assignment 1. Read in TECH 316, Filtration, in this series or in another authoritativo source a discussion ot filtration and ignition of precipitates. (3) The student essentially eliminated the d- gestion period because it was evident that a large amount of precipitate had formed immediately upon addition of the BaCla solution. 2. A student was in a rush to complote this experi- ment and made some minor changes in the proce- dure, as described below. Explain the effects, if any. these changes could have had on the results (1) The student mixed 1 mL of concentrated nitric acid (HNO3) with the dissolved sample instead of 1 ml of concentrated HCI acid as directed, be- cause the reagent bottle of HCI was empty. (4) To hasten the ignition process, the stude transterred the wet filter paper and precipitate to crucible to which the full heat of the burner was i mediately applied. The filter paper flared up pieces of it floated out of the crucible and onto laboratory bench. (2) In order to do the determination in triplicate, the student quickly poured 15 mL of the BaCl2 pre- cipitating reagent into each of three samples prior t0 any heating, swirled the mixtures a tew times, and al- lowed the precipitates that formed to settle. ANAL 356/Gravimetric Determination of SulfateExplanation / Answer
It would depend on the information you have about the sample, but in the case of what the student did in 1, it would alter solubility mainly. If the sample required HCl so as to form the precipitate, then the reaction with HNO3, even if it is still an acid, would turn into another product that will precipitate. If what’s required to filtrate is said specific precipitate then the whole experiment will be wrong. If not, another kind of reaction will be needed so as to get the element in question from the nitrate that will be formed.
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