Question

Determine Delta G for the following reactions.

a) Antimony pentachloride decomposes at 448oC. The reaction is: SbCl5(g)-->SbCl3(g)+Cl2(g)

An equilibrium mixture in a 5.00 L flask at 448oC contains 3.85g of SbCl5, 9.14g of SbCl3, and 2.84g of Cl2.

b) Chlorine molecules dissociate according to this reaction: Cl2(g)-->2Cl(g)

1.00% of Cl2 molectules dissociate at 975K and a pressure of 1.00 atm.

Answer 1

that ideal gas equation is PV = nRT

Where

T = Temperature = 448 oC = 448+273 = 721 K

P = pressure = ?

n = No . of moles = mass/molar mass

R = gas constant = 0.0821 L atm / mol - K

V= Volume of the gas = 5.00L

So p = nRT / V

       = ( mass/molar mass) x (RT/V)

For SbCl5 , p = (3.85 / 299) x ( 0.0821x721) /5.00

                    = 0.152 atm

For SbCl3 , p' = (9.14 / 228) x ( 0.0821x721) /5.00

                    = 0.475 atm

For Cl2 , p'' = (2.84 / 71) x ( 0.0821x721) /5.00

                    = 0.473 atm

SbCl5(g)-->SbCl3(g)+Cl2(g)

Equilibrium constant , Kp = (pSbCl3 x pCl2) / p SbCl5

                                     = (p' x p'') / p

                                     = 1.48

We know that delta G = -RT lnKp

                                = 8.314J/(mol-K) x 721 K x ln 1.48

                                = 2349.4 J/mol