16. O/N 2017/P11/Q31
Octane, C8H18, is a hydrocarbon that undergoes combustion in a petrol engine.
...W...C8H18 + ...X...O2 → ...Y...CO2 + ...Z...H2O
Which row shows the figures needed to balance the equation?
Answer: D
Explaination
The above equation shows complete combustion of alkane (octane) molecule as there is an excess of oxygen supply, the product are CO2 and H2O.
STEPS FOR BALANCING EQUATION
Step 1: number of C atoms become moles of CO2.
Step 2: number of H atoms/2 becomes moles of H2O.
Step 3: total O2 on right hand side/2 becomes moles of O2 on left hand side.
The final equation will be on multiplying by 2 the entire equation.
C8H18 + 12.5O2 -------------->8CO2 + 9H20
(1 x2) (12.5 × 2= 25) (8×2= 16) (9×2= 18)
2C8H18 + 25O2 -------------->16CO2 + 18H20
