Tutored Practice Problem 3.5.4 Use stoichiometric methods to analyze a mixture.

Question

Tutored Practice Problem 3.5.4 Use stoichiometric methods to analyze a mixture. Close Problem of CuBr2 and inert material is analyzed to determine the Cu content. First the mixture is dissolved in water. Then all of the A mixture bromide ion is precipitated as AgBr by the addition of an excess of silver nitrate. CuBr (aq)+2AgNO,(ag)-2AgBres)+ Cu(NOy)(a In one experiment, a 0.6957 g sample of the mixture resulted in 0.9735 g of AgBr. Determine the percent (by mass) of Cu in the mixture. Show Approach MacBook Air E9 F7 F6 0,3 FS

Explanation / Answer

Moles of AgBr formed = mass/molecular weight

= 0.9735g / 187.77 g/mol

= 0.00518 mol

From the stoichiometry of the reaction

2 moles of AgBr formed from = 1 mol of CuBr2

0.00518 mol of AgBr formed from = 1*0.00518/2

= 0.00259 mol of CuBr2

Mass of CuBr2 = moles x molecular weight

= 0.00259 mol x 223.37 g/mol

= 0.5790 g

Mass of Cu in CuBr2 = 63.546*0.5790/223.37 = 0.1647 g

Mass% of Cu in the sample

= mass of Cu*100/mass of sample

= 0.1647*100/0.6957

= 23.676%

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