How to find the Order of a Reaction using this table.

Time (s) [O2] (M)
0.00 0.00
6.00 x 103 2.1 x 10-3
1.20 x 103 3.6 x 10-3
1.80 x 103 4.8 x 10-3
2.40 x 103 5.6 x 10-3
3.00 x 103 6.4 x 10-3
3.60 x 103 6.7 x 10-3
4.20 x 103 7.1 x 10-3
4.80 x 103 7.5 x 10-3
5.40 x 103 7.7 x 10-3
6.00 x 103 7.8 x 10-3

Whenever we have a table with the molarity of a substance against time, the best idea is to input the time into one cell of Excel and molarity into the other adjacent cell of Excel.

We wish to produce 3 plots: plot 1 would contain time on the x-axis and molarity values on the y-axis. In case we get a straight line in the graph, we can verify that this is a 0th order reaction.

Plot 2 would need us to calculate the natural logarithm of each concentration and plot time on the x-axis and ln of each molarity on the y-axis. In case we get a straight line, we can verify a 1st order reaction.

Plot 3 would require calculating the reciprocal of each molarity, that is, 1/[O2] in each case. Plotting time on the x-axis and 1/[O2] on the y-axis would yield a graph. In case this graph is linear, then the reaction order is 2nd.

We plot each graph and add trendline in Excel. None of the graphs is perfectly linear, so the only data we can rely on is the R-squared coefficient. The closer it is to 0, the closer your points resemble a line. Out of all three graphs, the highest R-squared value is seen for the 0th order rate law at a value of 0.8721 against 0.7749 for the 1st and 0.6255 for the second.

You may wish to refer to the Excel file for the details.