For the reaction: CH4+2O2 --> 2H2O + CO2 + heat, where 16 g of CH4 reacts to form 36 g of H2O and 44 g of CO2, what is the mass of O2 required?

The equation of the chemical reaction given
is:

CH4 + 2O2 --> 2H2O + CO2 +
heat

The equation is balanced as the number of atoms of
each element are the same on both the sides.

It can be seen
that for each mole of CH4, two moles of O2 are
required.

The molar mass of CH4 is 16, that of O2 is 32,
H2O has a molar mas of 18 and CO2 has a molar mass of
44.

As 16 grams of CH4 are reacting, the number of moles of
CH4 is one. For this 2 moles of O2 are required. The mass of 2 moles of O2 is 64
g.

The mass of oxygen required for the given
reaction is 64 g.