15 grams of hydrogen and 7.5 grams of oxygen were placed in a beaker. An explosion happened inside the baker that produced water. The beaker was never opened. How many grams of water were produced?

16.8768 g

Explanation:

The reaction that takes place is:

First we convert the mass of hydrogen and oxygen into moles, using their respective molar masses:

There are significantly less oxygen moles than hydrogen moles, so oxygen is the limiting reactant.

We calculate the produced moles of water, using the moles of the limiting reactant:

Finally we convert water moles into grams, using its molar mass: