Question

At 25°C in a 25 mL Erlenmeyer flask were combined 1.200 g of solid copper (II) chloride dehydrate, 1.2 mL of 2,4-pentanedione, C5H8O2, 5.00 mL of 0.800 M aqueous solution of sodium acetate, and 10.0 mL of water. After stirring for 35 minutes at 25°C, 0.200 g of solid bis(2,4-pentanedionato)copper(II), Cu(C5H7O2)2, was isolated. What was the percent yield of the solid product? At 25°C, the densities of 2,4-pentanedione and water are 0.975 g/mL and 0.997 g/mL, respectively. The unbalanced equation for the reaction is shown below.

Cu+2(aq) + C5H8O2(aq) + C2H3O2-(aq) → Cu(C5H7O2)2(s) + HC2H3O2(aq)

Answer 1

change all to moles:

mol of copper (II) chloride dehydrate= mass/MW = 1.2/134.45 = 0.008925 mol of CuCl2

mass of pentadione = D*V = 1.2*0.975 = 1.17 g

mol of pentanedione = mass/MW = 1.17 /100.1158 = 0.01168 mol of C5H8O2

acetate = MV = (0.8*5*10^-3) = 0.004 mol of acetate...

Compare stoichoiemtric ratios:

Cu+2(aq) + 2C5H8O2(aq) + 2C2H3O2-(aq) → Cu(C5H7O2)2(s) + 2HC2H3O2(aq)

0.008925 mol of Cu + 0.01168/2 = 0.00584 mol of C5H8O2+0.004/2 = 0.002 mol of acetate

acetate is limiting reaction; so

0.004 mol of acetate = 0.002 mol of solid Cu(C5H7O2)2(s)

after reaction:

m = 0.2 g of solid is formed

mol of soli d= mass/MW = 0.2/261.7618 = 0.000764 mol of solid

% yield = actual/theoretical *100% = 0.000764 /0.002 *100 = 38.2 %