Using 3 O2 molecules and 5 H2 molecules, how many water molecules can be produced? Do you have any left over?

5 molecules of H₂O can be produced

0.5 molecules of O₂ did not reacted

Explanation:

The reaction is:  2H₂(g)  +  O₂(g)  →  2H₂O (g)

Firstly we determine the limiting reactant:

2 moles of hydrogen need 1 mol of oxygen to react

We must know the moles of each.

6.02ₓ10²³ molecules is 1 mol

3 molecules are 3 /6.02ₓ10²³ = 4.98×10⁻²⁴ moles O₂

5 molecules are 5 / 6.02ₓ10²³ = 8.30×10⁻²⁴ moles H₂

2 moles of H₂ need 1 mol of O₂

Then 8.30×10⁻²⁴ moles of H₂ must need (8.30×10⁻²⁴ .1) / 2 = 4.15×10⁻²⁴ moles O₂. It is ok, because I have 4.98×10⁻²⁴ moles O₂. Oxygen is the reagent in excess, so the limiting is the H₂

1 moles of O₂ needs 2 moles of H₂ to react

Then, 4.98×10⁻²⁴ moles of O₂ must need (4.98×10⁻²⁴ .2) / 1 =9.96×10⁻²⁴ moles of H₂, we don't have enough H₂

So, in the reaction ratio is 2:2.

8.30×10⁻²⁴ moles of H₂ will produce 8.30×10⁻²⁴ moles H₂O

1 mol has 6.02×10²³ molecules

8.30×10⁻²⁴ must have (8.30×10⁻²⁴ . NA) = 5 molecules

The reagent in excess is the O₂. These means that there is oxygen that has not reacted.

We have 4.98×10⁻²⁴ moles O₂ and we used 4.15×10⁻²⁴ moles.

(4.98×10⁻²⁴ - 4.15×10⁻²⁴) = 0.83×10⁻²⁴ moles of oxgen hasn't reacted.

1 mol is contained by NA molecules

0.83×10⁻²⁴ moles are contained by (0.83×10⁻²⁴ . 6.02×10²³) = 0.5 molecules

From 3 O2 molecules and 5 H2 molecules we can make 5 H2O molecules.

There remains 1 O-atom

Explanation:

Step 1: Data given

Number of O2 molecules = 3

Number of H2 molecules = 5

Step 2:

1 water molecule contains 1 H2 molecules and 1 O- atom

In 3 O2 molecules we have 6 O-atoms

In 5 H2 molecules we have 10 H-atoms

1 water molecules contains 2 H- atomes and 1 O-atom

From 3 O2 molecules and 5 H2 molecules we can make 5 H2O molecules.

There remains 1 O-atom

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