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 62.1 g of k3po4 is produced and 80.8 g of h3po4 remains un reacted.

a) what is the starting mass of koh?

b)what is the starting mass of h3po4?

(a) Starting mass of KOH is 187.7g

(b) Starting mass of H3PO4 is 109.5g

Explanation:

From the equation of reaction,

1 mole (98g) of H3PO4 was used up to produce 1 mole (212g) of K3PO4

Mass of H3PO4 used up to produce 62.1g of K3PO4 = 98×62.1/212 = 28.7g of H3PO4

Starting mass of H3PO4 = mass of H3PO4 used up + mass of unreacted H3PO4 = 28.7g + 80.8g = 109.5g

Also, from the equation of reaction,

3 moles (168g) of KOH reacted with 1 mole (98g) of H3PO4

Starting mass of KOH that reacted with 109.5g of H3PO4 = 168×109.5/98 = 187.7g of KOH