27.29%
Now, to know the percent composition of Carbon and Oxygen . We will divide their weight with the total weight of CO2. % C = 12.01/44.01 = 0.2729= 27.29% (we will divide 0.2729 with 100 to take the percentage). % O = 32.00/44.01 =0.7271 =72.71 %O in CO2.
