Step 1 - Finding the stoichiometry of the reaction
The given reaction is:
[tex]3Pb(NO_3)_2+2\text{AlCl}_3\to3\text{PbCl}_2+2Al(NO_3)_3[/tex]
The stoichiometry of the reaction can be found by the bigger numbers that come before the formula of the substances:
3 moles of Pb(NO3)2 react with 2 moles of AlCl3 thus producing 3 moles of PbCl2 and 2 moles of Al(NO3)3
Step 2 - Using the stoichiometry to solve the question
The stoichiometry of a reaction works like a cake recipe. It defines a fixed proportion between the reactants and the products. We can thus use it to predict how much moles of Pb(NO3)2 would be needed.
In step 1, we have stated that:
3 moles of Pb(NO3)2 produce 2 moles of Al(NO3)3
Now let's set the following proportion:
[tex]\begin{gathered} 3\text{ moles of Pb(NO3)2 produce --- 2 moles of Al(NO3)3} \\ x\text{ moles ----------------- 12 moles of Al(NO3)3} \\ \\ x=\frac{12\times3}{2}=18\text{ moles} \end{gathered}[/tex]
Therefore, 18 moles of Pb(NO3)2 would be required.
