Question

(a) Consider the combustion of butane, given below: 2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g) If C4H10(g) is decreasing at the rate of 0.850 mol/s, what are the rates of change of O2(g), CO2(g), and H2O(g)?

O2(g)/t = mol/s

CO2(g)/t = mol/s

H2O(g)/t = mol/s

(b) The decomposition reaction given below: 2 IF5(g) 1 I2(g) + 5 F2(g) is carried out in a closed reaction vessel. If the partial pressure of IF5(g) is decreasing at the rate of 470. torr/min, what is the rate of change of the total pressure in the vessel?

Ptot /t = torr/min

Answer 1

a) rate of reaction = ( -1/2) d[C4H10]/[ dt = -( 1/13) d[O2] / dt = ( 1/8) d[CO2] / dt = ( 1/10) d[H2O] / dt

given - d[C4H10] /dt = -0.85 mol/s

d[O2] /dt = ( 13/2) ( d[C4H10] / dt   = - 5.525 mol/s     ( -ve sign indicates decreasing )

d[CO2] /dt = ( 8/2) (- d[C4H10] / dt = ( 4 x 0.85) = 3.4

d[H2O] /dt = (10/2) ( -d[C4H10] /dt = ( 10/2) x 0.85 =4.25

b) d [IF5] / dt = -0.47 torr /min

rate of rxn = - ( 1/2) d[IF5]/dt = d[I2] /dt = ( 1/5) d[F2] / dt

d[O2] /dt = ( -1/2) ( -0.47) = 0.235 torr/min

d[F2] /dt = -( 5/2) d[IF5]/dt = ( -5/2) ( -0.47) = 1.175 torr /min

total Pressure rate change is addig all three d[IF5]/dt + d[I2] /dt + d[F3]/dt

     = -0.47 + 0.235 + 1.175 = 0.94 torr /min