Question
Practice Problem BUILD Potassium hydroxide and phosphoric acid react to form potassium phosphate and water according to the equation
. Determine the starting mass of each reactant if
are produced and
remain unreacted.
Ask by Conner Howell. in the United States
Jan 23,2025
Upstudy AI Solution
Tutor-Verified Answer
Answer
Starting mass of KOH: 44.2 g
Starting mass of H₃PO₄: 115.6 g
Starting mass of H₃PO₄: 115.6 g
Solution

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Bonus Knowledge
To find the starting mass of each reactant in the reaction, we can use stoichiometry and the given information. The balanced equation shows that 3 moles of KOH react with 1 mole of H3PO4 to produce 1 mole of K3PO4 and 3 moles of water.
First, we need to determine how many moles of K3PO4 were produced:
- The molar mass of K3PO4 is approximately
. - Moles of K3PO4 =
.
From the stoichiometry of the balanced equation:
- To produce 0.262 mol of K3PO4, we need:
- 0.262 mol
= 0.786 mol of KOH. - 0.262 mol of H3PO4.
- 0.262 mol
Next, we calculate the mass of KOH and H3PO4:
-
Molar mass of KOH is approximately
: - Mass of KOH =
.
- Mass of KOH =
-
Molar mass of H3PO4 is approximately
: - Moles of H3PO4 needed =
(from earlier). - Mass of H3PO4 =
.
- Moles of H3PO4 needed =
However, it is stated that
of H3PO4 remains unreacted. Thus, the starting mass of H3PO4 must be the sum of the reacted amount and the remaining amount:
- Total mass of H3PO4 =
.
In summary:
- Starting mass of KOH =
. - Starting mass of H3PO4 =
.