#### Corks Lab Example

In lab we often do the cork experiment where we find the order of reaction for the blue colored corks when they are tossed back and forth for 20 seconds. Use the data given below to calculate the order of the blue corks with its uncertainty.

Expt.#W
Before
#B
Before
#Blanks
Before
#B
After
Average
#B
TimeInit. Rate
#13030407,13,1210.720 sec0.533
#230502020,19,212020 sec1.000
#33070025,31,343020 sec1.500

Expt.[W][B]Rate
#10.3000.3000.533
#20.3000.5001.000
#30.3000.7001.500

Remember:

rate = k[W]x[B]y

When dividing one rate by another the k will always cancel and, if one of the concentrations remains constant, it will also cancel. In this case the k and [W]x will always cancel.

rate2/rate1 = 1.0/0.533 = (0.5)y/(0.3)y = (0.5/0.3)y

⇒   1.875 =(1.67)y ⇒  ln(1.875)=y[ln(1.67)] and y = (ln 1.875)/(ln 1.67) = 1.226

rate2/rate3 = 1.0/1.5 = (0.5)y/(0.7)y = (0.5/0.7)y

⇒   0.667 =(0.714)y ⇒  ln(0.667)=y[ln(0.714)] and y = (ln 0.667)/(ln 0.714) = 1.204

rate1/rate3 = 0.533/1.5 = (0.3)y/(0.7)y = (0.3/0.7 )y

⇒   0.355 =(0.429)y ⇒  ln(0.355)=y[ln(0.429)] and y = (ln 0.355)/(ln 0.429) = 1.222

Average y = 1.2174, range = 0.022, ± = range/2 = 0.011

⇒   Result = average ± range/2 = 1.2174 ± 0.011

Or, when properly rounded y = 1.22 ± 0.02