Chem 1211Take Home Quiz Name Titratrions 5 pts You wish to d

Chem 1211-Take Home Quiz Name Titratrions (5 pts) You wish to determine the weight percent of copper in a copis added d in a copper-containing alloy. After dissolving a sample of an alloy in nitrie acid, an excess of N reaction occurs: 2Cu(NO3)2(ag) Nal3raq) + 4 NaN03 (aq) + 5 Nal rag, 2Cu1@ .. + the equation: d the breaction is then titrated with sodium thiosulfate according to +3 Nal (aq) If 26.32 mL of 0.101 M weight percent of Cu in 0.251 g of the alloy Na,S,0, is requi

Solution

HERE ,moles Na2S2O3 = M Na2S2O3 x L Na2S2O3 = (0.101)(0.02632) = 0.00266 moles Na2S2O3

The titration reaction equation tells us that 2 moles of Na2S2O3 react with 1 mole of I3-.

0.00266 moles Na2S2O3 x (1 mole I3- / 2 moles Na2S2O3) = 0.00133 moles I3-

The initial reaction between Cu2+ and I- shows that it takes 2 moles of Cu2+ to produce 1 mole of I3-.

0.00133 moles I3- x (2 moles Cu2+ / 1 mole I3-) = 0.00266 moles Cu2+ which came from dissolving the Cu in the sample

0.00266 moles Cu x (63.5 g Cu / 1 mole Cu) = 0.169 g Cu

%Cu = (g Cu / g sample) x 100 = (0.169 / 0.252) x 100 = 67.0% Cu