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 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?

Answer 1

The starting mass of KOH was 113.8 g and the starting mass of H3PO4 was 143.9 g, calculated using stoichiometry based on the balanced equation for the reaction between KOH and H3PO4 where 62.1 g of K3PO4 is produced.

Step-by-step explanation:

To solve for the starting masses of reactants in the reaction between potassium hydroxide (KOH) and phosphoric acid (H3PO4), we will use stoichiometry based on the balanced chemical equation:

3KOH(aq) + H3PO4(aq) ⇆ K3PO4(aq) + 3H2O(l)

Given that 62.1 g of K3PO4 are produced:

Calculate moles of K3PO4 using its molar mass (molar mass of K3PO4 = 212.27 g/mol).

Use the stoichiometry of the balanced equation to find the moles of KOH required (3 moles of KOH per mole of K3PO4).

Then, calculate the starting mass of KOH using the molar mass of KOH (molar mass of KOH = 56.11 g/mol).

For the starting mass of H3PO4:

The unreacted mass is 80.8 g, so add this to the mass of H3PO4 that reacted (calculated by stoichiometry from the produced K3PO4) to find the starting mass.

By performing these calculations:

A) The starting mass of KOH was 113.8 g.

B) The starting mass of H3PO4 was 143.9 g.

Answer 2

A). The starting mass of KOH = 49.2g

B). The starting mass of H3PO4 = 109.5g

Step-by-step explanation:

Given;

Molar mass of KOH = 56g/mol

Molar mass of H3PO4 = 98g/mol

Molar mass of K3PO4 = 212g/mol

Mass of K3PO4 produced = 62.1g

Mass of unreacted H3PO4 = 80.8g

Mole ratio of KOH : H3PO4 : K3PO4 = 3:1:1

Number of moles = mass/molar mass .....1

Using equation 1.

Number of moles of K3PO4 produced

N = 62.1g/212g/mol = 0.293 mol

Therefore: using the mole ratio in the reaction;

Mass of H3PO4 reacted = number of moles × molar mass ...2

M = 1×0.293mol×98g/mol

M = 28.7g

Total mass of H3PO4 = mass of reacted + mass of unreacted H3PO4.

Total mass = 28.7g + 80.8g = 109.5g

Starting mass of H3PO4 = 109.5g

Also for KOH,

Mass of reacted KOH = number of moles × molar mass

Since 3 moles of KOH will produce 1 mole of K3PO4.

3 × 0.293 moles of KOH will produce 0.293 moles of K3PO4.

Number of moles of KOH = 3 × 0.293moles = 0.879mole

Mass of reacted KOH = 0.879 mol × 56g/mol = 49.2g

Since there are no unreacted KOH.

Starting mass of KOH = 49.2g