Question

A hydrogen-filled balloon was ignited and 1.80 g of hydrogen reacted with 14.4 g of oxygen. How many grams of water vapor were formed?

Answer 1

Hydrogen reacts with water according to the following equation:
2H2 + O2 ..............> 2H2O

From the periodic table:
molar mass of hydrogen = 1 gram
molar mass of oxygen = 16 grams

Therefore:
4 grams of hydrogen react with 32 grams of oxygen to produce 36 grams of water vapor.

Now, we need to determine the limiting reactant in the equation. By comparing, we can deduce that hydrogen is the limiting reactant (because half of that amount is less than how much O2 you have).
This means that, once the amount of the reacting hydrogen is consumed, the reaction will stop. So, our calculations will be based on the amount of reacting hydrogen.

Now, back to our calculations:
we know that 4 grams of hydrogen are needed to produce 36 grams of water vapor.
To know how many grams of water vapor were produced from 1.8 grams of hydrogen, we will use cross multiplication as follows:
mass of water vapor = (1.8 x 36) / 4 = 16.2 grams