Question

DATA SHEET Overall Stoichiometric Equations 1. Results and Observations 2. Unknown No.:l Concentration of standard Na2S&O3 solution, M 0.020(0 Trial 3 Trial 2 Trial 1 13.22 33.97 o.0.20 1311 Initial burette reading, mL 13.09 Final burette reading, mL (0.21 Volume of NAS2O3 used, mL Amount of NA2S2O3 used, mol Amount of Cu2 in unknown sample, mol L0.00 10. 00 10.00 Volume of original Cu solution used, mL in original solution, M Concentration of Cu Average Concentration of Cu2, M

Answer 1

Trial 1.

Part 1.

Moles of Na2S2O3 = (10.21/1000) L * 0.0206 mol/L = 2.1*10^-4 mol

Part 2.

Moles of Cu²⁺ = same as that of Na2S2O3 = 2.1*10^-4 mol

Part 3.

Original concentration of Cu²⁺ = 2.1*10^-4 mol*1000/(10+10.21) L = 0.010407 M

Part 4.

Average concentration of original Cu²⁺ solution = (Original concentration of Cu²⁺ in Trial 1 + Original concentration of Cu²⁺ in Trial 2 + Original concentration of Cu²⁺ in Trial 3)/3