Based on the equation provided, 3 mol KOH will react with 1 mol H3PO4 to form the products of the reaction.
We are starting with 43.5 g of KOH, but need to convert that to moles to determine how much H3PO4 will react with it. We can use the periodic table to determine that 1 mole of KOH weighs 56.1 grams and use that as a conversion factor.
1 mole KOH
43.5 g KOH • 56.1 g KOH = 0.775 mol KOH
Now that we know we have 0.775 mol of KOH, how much H3PO4 needs to react with it? 3 times as much KOH as H3PO4 will be needed based on those coefficient ratios.
1 mol H3PO4
0.775 mol KOH • 3 mol KOH = 0.258 mol H3PO4
Now we know that 0.258 mol H3PO4 will fully react with 0.775 mol KOH, how much is that in grams? Same as before, we are using the periodic table to determine that 1 mole of H3PO4 weighs about 98 grams. Notice that the conversion factor is used differently based on the units of measurement we want to cancel out.
98 g H3PO4
0.258 mol H3PO4 • 1 mole H3PO4 = 25.284 g H3PO4
