Calcium hydroxide reacts with sodium phosphate to produce calcium phosphate and sodium hydroxide. If 100 grams of calcium hydroxide reacts with 100 grams of sodium phosphate,

Question

determine the amount of each chemical present when the reaction is complete

Grams calcium hydroxide =?

Grams of sodium phosphate=?

Grams of calcium phosphate=?

Grams of sodium hydroxide?

Mass reactants=?

Mass after reaction?

Answer 1

3Ca(OH)₂ + 2Na₃PO₄ ==> Ca₃(PO₄)₂ + 6NaOH ... balanced equation

First, find the limiting reactant:

moles Ca(OH)₂ present = 100 g x 1 mole/74.09 g = 1.35 moles (divided by 3-->0.45)

moles Na₃PO₄ present = 100 g x 1 mole/163.9 g = 0.610 moles (divided by 2-->0.31)

LIMITING reactant is Na₃PO₄

There will be zero grams Na3PO4 left after the reaction

For grams Ca(OH)2 left: 0.610 mol NaP x 3 mol Ca(OH)2/2 mol NaP = 0.915 mol Ca(OH)3 used up

Grams left over: 1.35 mol - 0.915 mol = 0.435 mol x 74.09 g/mol = 32 g left over (30 g if use 1 sig. fig.)

For grams of calcium phosphate left: 0.610 mol NaP x 1 mol CaP/2 mol NaP = 0.305 mol CaP formed

Grams at end of rx: 0.305 moles CaP x 310 g/mol = 94 g (90 g if use 1 sig. fig.)

For grams NaOH left: 0.610 mol NaP x 6 mol NaOH/2 mol NaP = 1.83 moles NaOH formed

Grams at end of rx: 1.83 moles NaOH x 40 g/mol = 73 g (70 g if use 1 sig. fig.)