The balanced reaction equation for combustion of Mg is: 2 Mg + O2 --> 2 MgO.
In the reaction vessel you have 1.0 moles of Mg and 0.30 moles of O2. What is the limiting reactant? How many moles of MgO can you possibley make?
Here is a worked example of a simple stoichiometry problem. Follow the steps.
http://www.jiskha.com/science/chemistry/stoichiometry.html
Use the procedure twice, once for one reactant and next for the other reactant. This will give you two answers for moles CO2; the smaller one is the correct value to choose and the reactant giving that value is the limiting reagent.
To determine the limiting reactant, we need to compare the stoichiometric coefficients of the reactants in the balanced equation to the given amounts.
The stoichiometric ratio between Mg and O2 in the balanced equation is 2:1. This means that for every 2 moles of Mg, we need 1 mole of O2 to react completely.
Given:
- Moles of Mg = 1.0 moles
- Moles of O2 = 0.30 moles
To find the limiting reactant, we can compare the moles of each reactant present to the stoichiometric ratio.
For Mg:
- Given moles: 1.0 moles
- Stoichiometric coefficient: 2
For O2:
- Given moles: 0.30 moles
- Stoichiometric coefficient: 1
To determine which reactant is limiting, we compare the number of moles available with respect to the stoichiometric ratio.
For Mg:
1.0 moles / 2 = 0.50 moles Mg are needed for complete reaction
For O2:
0.30 moles / 1 = 0.30 moles O2 are needed for complete reaction
From the calculations, we can see that we have more moles of Mg (1.0 moles) compared to the stoichiometric ratio requirement of 0.50 moles. However, we have fewer moles of O2 (0.30 moles) compared to the stoichiometric ratio requirement of 0.30 moles. Therefore, oxygen (O2) is the limiting reactant in this reaction.
To calculate the maximum amount of product (MgO) that can be formed, we will use the mole ratio between Mg and MgO from the balanced equation, which is 2:2 or 1:1.
Since oxygen (O2) is the limiting reactant, its moles will determine the maximum moles of product formed.
Therefore, the maximum moles of MgO produced will be equal to the moles of O2, which is 0.30 moles.
In conclusion:
- The limiting reactant is oxygen (O2).
- The maximum moles of MgO that can be produced is 0.30 moles.