# In the explosion of a hydrogen filled balloon, .10 g of hydrogen reacted with .80 g of oxygen. How many grams of water vapor are formed? Water vapor is the only product.

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The equation for this reaction is:

`2H_2 + O_2 -gt 2 H_2O `

When given masses of the two reactants you must determine if one reactant is in excess of the amount needed.  If so, the limiting reactant determines how much product will form.

The mole ratio of H2 to O2, according to the equation, is 2:1. We can determine the limiting reactant by calculating the moles of each reactant and comparing them to this ratio.

`(0.10g H_2)/1 x (1 mol)/(2g) = 0.050 mol H_2`

`(0.80g O_2)/1 x (1mol)/(32g) = 0.025mol O_2`

We have the correct stoichiometric ratio of 2 moles H2 to 1 mole O2 so there isn't one limiting reactant. We can use the amount of either reactant to determine the mass of water vapor produced:

`(0.050mol H_2)/1 x (2 H_2O)/(2 H_2) x (18g)/(1 mol) = 0.90g H_2O`

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