Alessandro V. answered • 04/24/23
PhD in Chemistry with 10+ Years of Teaching Experience
This is a limiting reactant problem. The reason you can immediately tell it's a limiting reactant problem is because of the word 'excess' used in reference to phosphoric acid. That means the other reactant, barium chloride, is the limiting one.
The first step is to write the full chemical reaction and balance the equation. That way you will be able to see the molar ratio between barium chloride and barium phosphate. The equation is provided, it just needs to be balanced.
The second step is to calculate is to calculate the number of moles of barium chloride. You are given molarity and volume. Remember, molarity is defined by the number of moles of solute (barium chloride) divided by the liters of solution. Therefore, you can calculate the number of moles multiplying volumes times molarity (3.68 L x 0.192 moles/L = number of moles of barium chloride).
The last step is to multiply the number of of moles barium chloride (calculated in step 2) times the molar ratio (the molar ratio is the stoichiometric coefficient of barium phosphate divided by the stoichiometric coefficient of barium chloride. Hint: it's 1/3).
Hope that helps!
