mols KOH = M x L = ?
mols H3PO4 = 1/3 mols KOH (look at the coefficients in the equation).
M H3PO4 = mols H3PO4/L H3PO4.
What was the concentration of the unknown H3PO4 solution (answer in M).
H3PO4(aq) + 3KOH(aq) --> 3H2O(l) + K3PO4(aq)
mols H3PO4 = 1/3 mols KOH (look at the coefficients in the equation).
M H3PO4 = mols H3PO4/L H3PO4.
1. Write the balanced equation for the reaction:
H3PO4(aq) + 3KOH(aq) โ 3H2O(l) + K3PO4(aq)
2. Determine the stoichiometric ratio between H3PO4 and KOH. According to the balanced equation, 1 mole of H3PO4 reacts with 3 moles of KOH.
3. Convert the volume of KOH solution to moles. The molarity (M) of a solution is given by moles of solute divided by the volume of the solution in liters.
Moles of KOH = molarity (KOH) ร volume (KOH solution in liters)
= 0.140 M ร 0.116 L
= 0.01624 moles
4. Apply the stoichiometric ratio to calculate the moles of H3PO4. Since the stoichiometric ratio is 1:3 between H3PO4 and KOH, the moles of H3PO4 will be one-third of the moles of KOH.
Moles of H3PO4 = (1/3) ร moles of KOH
= (1/3) ร 0.01624
= 0.00541 moles
5. Calculate the concentration of H3PO4. The concentration (M) is given by moles of solute divided by the volume of the solution in liters.
Concentration (H3PO4) = moles of H3PO4 / volume (H3PO4 solution in liters)
= 0.00541 moles / (11.0 mL รท 1000)
= 0.491 M
Therefore, the concentration of the unknown H3PO4 solution is 0.491 M.