In a titration of 35 mL of 0.40 M H3PO4 with 0.30 M KOH solution, what volume (in mL) of KOH solution is needed to reach the last equivalence point (i.e., point in the titration where enough KOH has been added to neutralize all three of the acidic protons in the phosphoric acid)?
To find the volume of KOH solution needed to reach the last equivalence point, we can use the concept of stoichiometry. The balanced chemical equation for the reaction between H3PO4 and KOH is:
H3PO4 + 3 KOH -> K3PO4 + 3 H2O
From the balanced equation, we can see that 1 mole of H3PO4 reacts with 3 moles of KOH. Therefore, to neutralize all three acidic protons in phosphoric acid, we need three times the moles of KOH compared to H3PO4.
First, let's calculate the moles of H3PO4 present in the given volume:
moles of H3PO4 = volume (in liters) x molarity
= 0.035 L x 0.40 mol/L
= 0.014 mol
Since we need three times the moles of KOH as H3PO4, we can calculate the moles of KOH required:
moles of KOH = 3 x moles of H3PO4
= 3 x 0.014 mol
= 0.042 mol
Now, let's find the volume of KOH solution needed using the molarity and the calculated moles:
volume (in liters) = moles / molarity
= 0.042 mol / 0.30 mol/L
= 0.14 L
Finally, convert the volume from liters to milliliters:
volume (in mL) = 0.14 L x 1000 mL/L
= 140 mL
Therefore, 140 mL of KOH solution is needed to reach the last equivalence point.
To determine the volume of KOH solution needed to reach the last equivalence point in the titration, we need to use the concept of stoichiometry and the balanced chemical equation for the reaction between H3PO4 and KOH.
The balanced chemical equation for the reaction is:
H3PO4 + 3 KOH -> K3PO4 + 3 H2O
From the balanced equation, we can see that 1 mole of H3PO4 reacts with 3 moles of KOH. This implies that the molar ratio between H3PO4 and KOH is 1:3.
Now, let's calculate the number of moles of H3PO4 and KOH involved in the reaction:
Moles of H3PO4 = Volume (in L) of H3PO4 * Concentration (in M) of H3PO4
= 0.035 L * 0.40 M
= 0.014 mol
Since we have a 1:3 molar ratio between H3PO4 and KOH, the moles of KOH required to neutralize the H3PO4 is also 0.014 mol.
Now, let's calculate the volume (in L) of KOH solution required:
Volume (in L) of KOH = Moles of KOH / Concentration (in M) of KOH
= 0.014 mol / 0.30 M
= 0.0467 L
Finally, let's convert the volume from liters to milliliters:
Volume (in mL) of KOH = Volume (in L) of KOH * 1000
= 0.0467 L * 1000
= 46.7 mL
Therefore, 46.7 mL of KOH solution is needed to reach the last equivalence point in the titration.