Question

 

Determination of an Equivalent Mass by Electrolysis

Data

Identity of metal = Copper

Mass of metal anode = 11.167 g

Mass of anode after electrolysis = 10.930 g

Initial buret reading =50 mL

Buret reading after first electrolysis =49.2 mL

Buret reading after refilling = 50 mL

Buret reading after second electrolysis =47.2

Barometric pressure
(1 atm = 1013.25 mbar)

Temperature, T = 328 K

Vapor pressure of H2O at T=

Calculations (show work) Total volume of H2 produced, V=

Partial Pressure of dry H2=

(ignore any pressure effect due to liquid levels in buret)PH2= barometric pressure- PH2O

No. moles H2 produced, n=

Faradays passed (no. of moles of electrons)=

Loss in mass by anode=

Equivalent mass of metal=

mass lost/faradays passed

Molar mass of metal =

Charge, n, on cation=

Answer 1

Determination of an Equivalent Mass by Electrolysis

Data

Identity of metal      = Copper

Mass of metal anode    = 11.167 g

Mass of anode after electrolysis   = 10.930 g

Loss in mass by anode = 11.167 g - 10.930 g = 0.237 g

Initial burette reading    = 50 mL

Burette reading after first electrolysis = 49.2 mL

Buret reading after refilling = 50 mL

Buret reading after second electrolysis = 47.2

Total volume of H₂ = (49.2 mL + 47.2 ml) = 96.4ml

Barometric pressure

(1 atm = 1013.25 mbar)

Temperature, T = 328 K

Vapor pressure of H2O at 328 K = 0.15546 atm

Partial Pressure of dry H2

PH2= barometric pressure- PH2O

PH₂ 1atm - 0.15546atm   = 0.84454 atm

No. moles H2 produced, n=

We can calculate number of moles H₂ by using ideal gas equation

PV=nRT

R = 0.082 L atm K−1 mol−1

n = PV/RT

n= (0.84454atm x 0.0964L) /(0.082 L atm K−1 mol−1 x 328K) = 0.00303 moles

No. moles H2 produced, n= 0.00303 moles

Faradays passed (no. of moles of electrons)

1 mole H2 requires passage of 2 faradays

No. of faradays passed = .00303 moles x 2faradays/1mol H2 = 0.00606 faraday

Loss in mass by anode= 0.237 g

Equivalent mass of metal= mass lost/faradays passed

Equivalent mass of metal = 0.237 g/0.00606 = 39.1g/mol

Molar mass of metal = 2 x Equivalent mass = 2 x 39.1 =78.2 g/mol

Charge, n, on cation= 2

Molar mass of Cu is 63.546 g/mol . There is some error in experiment.