82 Chapter 4: Chemical Reactions and Solution Stoichiometry Baso. After addition

Question

82 Chapter 4: Chemical Reactions and Solution Stoichiometry Baso. After addition of an itate collected is 2.014 g. What is A mixture of BaCl, and NaCl is analyzed by precipitating all the barium as excess of Na,SO, to a 3.743-g sample of the mixture, the mass of precipitate co the mass percentage of barium chloride in the mixture? a) 60.32% b) 53.81% c) 31.65% d) 48.00% e) 13.07% 63. Ans: d Algorithm: Yes Chapter/Section: 4.7 Difficulty: Moderate Keyword 1: Chemistry Keyword 2: general chemistry Keyword 3: chemical reactions Keyword 4: quantitative analysis Keyword 5: gravimetric analysis 64. A 3.00-g sample of an alloy (containing only Pb and Sn) was dissolved in nitric acid (HNO,). Sulfuric acid was added to this solution, which precipitated 2.35 g of PbSO4. Assuming that all of the lead was precipitated, what is the percentage of Sn in the sample? (molar mass of PbSO4-303.3 a) 46.5% Sn b) 0.775% Sn c) 78.3% Sn 53.5% Sn e) 1.61%Sn Ans: a Algorithm: Yes Chapter/Section: 4.7 Difficulty: Moderate K Keyword 2: general chemistryKeyword 3: chemical reactions Keyword 5: gravimetric analysis A mixture contained no fluorine compound except methyl fluoroacetate, FCH 92.07 g/mol). When yword1 Chemi stry 65. chemically treated, all the fluorine was converted to CaF2 (molar

Explanation / Answer

BaCl2 + NaCl

m = 3.743 g

mass of BaSO4 = 2.014 g

mol of BaSO$ = masS/MW = 2.014/233.3896 = 0.008629

then, mol of BaCl2 = 0.00862 mol

mass of BaCl2 = mol*MW = 0.00862*208.23 = 1.79490 g

% BaCl2 = masS/Total mass *100% = 1.794 / 3.743*100 = 47.92 %

choose D = 48%

Q64

m = 3 g of alloy

mol of PbSO4 = masS/MW = 2.35/303.3 = 0.007748

mol of Pb = 0.007748

mass of Pb =? mol*MW = 0.007748*207.2 = 1.60538 g of Pb

% Sn = 100 - (1.60538)/3*100 = 46.48 %

choose A

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