When doing a limiting reagant problem, I need to determine to mole ratio, right? But the problem is if 19.6 g of H3PO4 reacted with 22.4 g KOH...
How do I get two separate mole ratios?
The answers are: 3/1 for H3PO4 and 3/3 for KOH, but why?
You balance the reaction equation.
H3PO4+3KOH>> K3PO4 + 3HOH
so you need 3 moles KOH for each mole phosporic acid.
figure the moles you have of each:
KOH=22.4g/56.1= about .4 you do it.
H3PO4=19.6/97about=about .5
so clearly, you do not have nearly enough KOH(you would need almost four times as muchas you have (.5*3/.4).
So the KOH is going to determine how much product you make.
Thank you.
To solve a limiting reagent problem, you need to determine the mole ratio between the reactants based on the balanced chemical equation. In this case, the balanced equation is:
H3PO4 + 3KOH → K3PO4 + 3H2O
To calculate the mole ratios, you need to convert the given masses of the reactants (in grams) to moles. Here's how you can do it:
1. Convert the mass of H3PO4 to moles:
- Use the molar mass of H3PO4, which is 98 g/mol.
- Divide the given mass (19.6 g) by the molar mass to get the number of moles.
Moles of H3PO4 = 19.6 g / 98 g/mol = 0.2 mol
2. Convert the mass of KOH to moles:
- Use the molar mass of KOH, which is 56.1 g/mol.
- Divide the given mass (22.4 g) by the molar mass to get the number of moles.
Moles of KOH = 22.4 g / 56.1 g/mol ≈ 0.4 mol
Now that you have the number of moles for each reactant, you can compare their mole ratios to determine the limiting reactant.
The mole ratio between H3PO4 and KOH can be derived from the balanced equation: 1 mole of H3PO4 reacts with 3 moles of KOH.
So, the mole ratio between H3PO4 and KOH is: 1/3.
Similarly, the mole ratio between KOH and H3PO4, using the inverse ratio, is: 3/1.
In your case, the correct answer is 3/1 for H3PO4 (meaning for every 3 moles of KOH, you need 1 mole of H3PO4), and 3/3 for KOH (meaning for every 3 moles of KOH, you need 3 moles of KOH).
By comparing the stoichiometric ratios (mole ratios) to the actual ratios of the given masses, you can determine the limiting reactant.