Question

re Submit for Grading Close Problem Tutored Practice Problem 3.5.4 ORE Use stoichiometric methods to analyze a mixture. A mixture of MgBry the addition of an excess of silver nitrate. and inert material is analyzed to determine the Mg content. First the mixture is dissolved in water. Then all of the bromide ion is precipitated as AgBr by MgBr2(aq)+2AgNOs(aq)2gBris) + Mg(NO3)2(aq) In one experiment, a 0.5572 g sample of the mixture resulted in 0.8532 g of AgBr. Determine the percent (by mass) of Mg in the mixture. %Mg Check & Submt Answer Show Approach

Answer 1

The balanced equation is

MgBr₂ (aq) + 2 AgNO₃ (aq) ---------> 2 AgBr (s) + Mg(NO₃)₂

Number of moles of AgBr = mass/mol.wt. = 0.8532 g/(187.77 g/mol) = 0.004544 mol

Accroding to balanced equation,

2 moles of AgBr produced from 1 mole of MgBr₂

So, 0.004544 mol of AgBr would be produced from 0.004544 mol * ½ = 0.002272 mol of MgBr₂

Number of moles of MgBr₂ = 0.002272 mol

Number of moles of Mg = 0.002272 mol

Mass of Mg = 0.002272 mol * 24.31 g/mol = 0.055231 g

Percent of Mg in the mixture = 0.055231 /0.5572*100 = 9.912164 % = 9.9 %