Question

How many grams of water will be produced if you start with 4.0 grams of hydrogen and an excess of oxygen given the following balanced chemical equation?
2H2 + O2 → 2H2O

Group of answer choices

A. 32.0 grams

B. 36.0 grams

C. 54.0 grams

D. 18.0 grams

Answer 1

Answer:

B.) 36.0 grams

Explanation:

To find the mass of water, you need to (1) convert grams H₂ to moles (using the molar mass), then (2) convert moles H₂ to moles H₂O (using mole-to-mole ratio from reaction coefficients), and then (3) convert moles H₂O to grams (using the molar mass). It is important to arrange the conversions in a way that allows for the cancellation of units.

Molar Mass (H₂): 2(1.008 g/mol)

Molar Mass (H₂): 2.016 g/mol

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

Molar Mass (H₂O): 18.014 g/mol

2 H₂ + O₂ -----> 2 H₂O
^                        ^

4.0 g H₂            1 mole             2 moles H₂O           18.014 g
---------------  x  ----------------  x  ------------------------  x  ---------------  = 36 g H₂O
                          2.016 g             2 moles H₂              1 mole