How many molecules of water will be produced if 52.6 g of methane are burned?

When the balanced reaction equation of methane combustion is:

CH4 + 2O2 →CO2 + 2H2O

so, we can see that each 1 mole of methane combusted will give 2 moles of water as a product.

so first, we need to get the moles of methane =
                                         
                         = mass of methane /molar mass of methane 

                         = 52.6 g / 16.04 g/mol

                         = 3.28 moles

when 1 mol of methane produces→ 2 moles of water 

∴ 3.28 moles methane produces →   X moles of water 

∴ moles of water = 3.28 * 2 

                             = 6.56 moles

when each 1 mole of water has 6.02 x 10^23 (Avogadro's number ) individual molecules:

∴number of molecules of water = 6.56 * 6.02 x 10^23

                                                      = 3.9 x 10^24 molecules