In the explosion of a hydrogen-filled balloon, 0.10 g of hydrogen reacted with 0.80 g of oxygen to form how many grams of water vapor? (Water vapor is the only product.) Express your answer using two significant figures.

Mass of water vapor produced : 0.90 g

Given

0.10 g of hydrogen reacted with 0.80 g of oxygen

Required

mass of water vapor produced

Solution

Reaction

2H₂ + O ⇒ 2H₂O

If we refer to the law of conservation of mass which states that the mass before and after the reaction is the same, then the mass of water vapor formed as a product is:

mass reactants = mass products

mass of Hydrogen + mass of Oxygen = mass of water vapor

0.1 g + 0.8 g = 0.90 g

Or we can also solve by using stochiometry (using the concept of moles) to find the mass of water vapor

he would use the colour black