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

25.33 grams of water are produced.

Explanation:

15 g H / 1.00784* = 14.8833 moles H

7.5 g O / 15.999** = 0.468779 moles O

Ratio of Hydrogen to Oxygen in Water: 2 : 1

Oxygen: 0.468779 moles

Hydrogen (calculated based on oxygen): 0.468779 * 2 = 0.937558 moles

Water: 0.468779 + 0.937558 = 1.406337 moles

Grams of water produced:

1.406337 mol * (water molar mass)

= 1.406337 mol * [2(1.00784) + 1(15.999)]

= 1.406337 mol * (18.01468***)

= 25.3347110272 g water

Notes:

*molar mass of hydrogen

**molar mass of oxygen

***molar mass of water is actually 18.01528, so the calculation of 18.01468 is close enough

Summary

Convert hydrogen and oxygen to moles.

Determine number of moles of water using: 2 mole hydrogen + 1 mole oxygen = 1 mole water

Convert water moles to grams.