HELP! URGENTLY NEEDED! The coefficient/s will balance the chemical equation CH4 +O2 » CO2 + H2O is

a
1, 2, 1, 2
b
2, 1, 1, 2
c
2, 2, 1, 1
d
1, 1, 1, 2

The coefficients : a. 1,2,1,2

Given

Reaction(unbalanced)

CH4 +O2 » CO2 + H2O

Required

The blanced equation

Solution

Give a coefficient

CH4 +aO2 » bCO2 + cH2O

Make an equation

C, left=1, right=b⇒b=1

H, left=4, right = 2c⇒2c=4⇒c=2

O, left=2a, right=2b+c⇒2a=2b+c⇒2a=2.1+2⇒a=2

The equation becomes :

CH4 +2O2 » CO2 + 2H2O

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.