The reaction between methane and oxygen produces water and carbon dioxide. If 3.2g of methane reacts with 12.8g of oxygen, what is mass of water...

Molar mass of methane (CH4) = 16
g/mole

Molar mass of Oxygen (O2) = 32
g/mole

Molar mass of water (H2O) = 18
g/mole

Molar mass of Carbon Dioxide (CO2) = 44
g/mole

Now, the balanced reaction is
:-

CH4(g) + 2O2(g)  ---------> CO2(g) +
2H2O(l)

Now, moles of CH4 reacting = mass of CH4/molar mass
of CH4 = 3.2/16 = 0.2

Moles of O2 reacting = mass of
O2/molar mass of O2 = 12.8/32 = 0.4

Now, As per the
balanced reaction, for complete reaction to occur, one mole of CH4 require 2 moles of
O2

Thus, 0.2 moles of CH4 requires 0.4 moles of
O2

Clearly, both CH4 & O2 are present in the exact
required quantity.

Hence, moles of CO2 formed = moles of
CH4 reacted = 0.2

Mass of CO2 formed = moles of CO2*Molar
mass of CO2 = 0.2*44 = 8.8 g

Moles of H2O formed = moles of
O2 reacted = 2*moles of CH4 reacted = 0.4

Thus, mass of H2O
formed = moles of H2O*molar mass of H2O = 0.4*18 = 7.2 g