Question

What mass of water is produced from the complete combustion of 4.60×10-3 g of methane?

Answer 1

Answer:

=  1.03 x 10⁻² g H₂O

Explanation:

To find the mass of water, you need to (1) convert grams CH₄ to moles CH₄ (via molar mass), then (2) convert moles CH₄ to moles H₂O (via mole-to-mole ratio from reaction coefficients), and then (3) convert moles H₂O to grams H₂O (via molar mass). The final answer should have 3 sig figs to reflect the given value (4.60 x 10⁻³ g).

Molar Mass (CH₄): 12.011 g/mol + 4(1.008 g/mol)

Molar Mass (CH₄): 16.043 g/mol

Combustion of Methane:

1 CH₄ + 2 O₂ ---> 2 H₂O + 1 CO₂

Molar Mass (H₂O): 2(1.008 g/mol) + 15.998 g/mol

Molar Mass (H₂O): 18.014 g/mol

4.60 x 10⁻³ g CH₄          1 mole             2 moles H₂O          18.014 g
--------------------------  x  -----------------  x  ---------------------  x  ----------------  =
                                     16.043 g            1 mole CH₄             1 mole

=  0.0103 g H₂O

=  1.03 x 10⁻² g H₂O