If you start with 5.0 grams each of hydrogen gas and oxygen gas, how many grams of water are produced?

Question

2H2 + O₂ ----> 2H₂O

Answer 1

Hello!

Lets begin by writing out a balenced equation for what happens when you mix H₂ and O₂:

2H₂(g) + O₂(g) --> 2H₂O(l)

Note that when writing an equation that each reagent is in units of mole.

Now, we started off with 5.0 grams each of hydrogen and oxygen gas so lets convert these to moles by dividing by the molar mass.

Molar Masses

H₂ = 2.02 g/mol

O₂ = 32.00 g/mol

Convert grams to moles!

5.0g H₂/(2.02 g/mol) = 2.475247525 molH₂

5.0g O₂/(32.00 g/mol) = 0.15625 molO₂

Now that we know how much of each reactant we have in moles, we can find our limiting reactant! The limiting reactant determines how much water we can make. To find the limiting reactant, use the chemical equation to convert our moles of reagent (H₂ and O₂) to moles of water. The limiting reagent will produce the smaller amount of H₂O.

(2.475247525 molH₂) x (2 molH₂O/2molH₂) = 2.475247525 molH₂O can be made from 0.5g of H₂ given that there is enough O₂ to make this happen

(0.15625 molO₂) x (2 molH₂O/1molO₂) = 0.3125 molH₂O can be made from 0.5g of O₂ given that there is enough H₂ to make this happen

0.3125 molH₂O < 2.475247525 molH₂O so it can be said that oxygen is our limiting reactant and we can only make as much as oxygen allows us to!

Now we know we can make 0.3125 molH₂O!

The last step is to convert moles of H₂O to grams of H₂O using the molar mass of water.

Molar Mass H₂O = 18.02g/mol

(0.3125 molH₂O) x (18.02g/mol) = 5.63grams of H₂O

Final answer: 5.63 grams of H₂O can be made from 5g of hydrogen and oxygen gas.

Hope this was helpful :)