Question

Potassium hydroxide and phosphoric acid react to form potassium phosphate and water according to the equation: 3KOH(aq) + H3PO₄(aq) → K3PO₄(aq) + 3H₂O(l). Determine the starting mass of each reactant if 59.9 g of K3PO₄ is produced and 85.3 g of H3PO₄ remains unreacted. What is the starting mass of KOH? (in grams) What is the starting mass of H3PO₄? (in grams)

Answer 1

The initial mass of KOH and H3PO4 used in the reaction can be calculated on the molar basis of the reaction between them. The starting mass of each reactant is found using stoichiometry and by considering the mass of the product K3PO4 formed and the unreacted H3PO4.

Step-by-step explanation:

To find the initial mass of KOH and H3PO4 used in the reaction, we need to use stoichiometry based on the chemical equation given: 3KOH + H3PO4 → K3PO4 + 3H2O. Since 59.9 g of K3PO4 was produced, we would work out the molar amount of K3PO4 produced and use the mole ratio from the equation to determine the moles of KOH used.

Knowing the molar mass of KOH, we can then find the mass of KOH that reacted. As for H3PO4, 85.3 g remained unreacted, so we need to add this to the mass of H3PO4 that reacted (calculated using the stoichiometry of the reaction) to find the starting mass.