Some Basic Concepts of Chemistry

The balanced equation for complete reaction is,
2C2H6+7O2→4CO2+6H2O
Moles of C2H6=‌

15g

30.07

=0.499mol
Moles of O2=‌

112

32

=3.50mol
Moles of O2 required for 0.499 mol of C2H6
0.499×‌

7

2

=1.747molO2
Since, 3.50mol,O2 is available and only 1.747 mol .
O2 is needed, C2H6 is limiting reactant. Mol of CO2 produced
0.499×‌

4

2

=0.998molCO2
mol of H2O produced
0.499×‌

6

2

=1.497molH2O
Moles of excess O2=3.50−1.747
=1.753mol
Total mol of gaseous substance, 0.998+1.497+1.753=4.25mol