how much volume of oxygen at stp in litres is required to burn 4g of methane gas completely

Answer 1

CH4 + 2O2 ==> CO2 + 2H2O

mols CH4 = grams/molar mass = ?
Using the coefficients in the balanced equation, convert mols CH4 to mols O2.
Now convert mols O2 to L O2 by mols O2 x 22.4 L/mol = L O2.

Answer 2

64.1