A 15.00 mL sample of an unknown monoprotic weak acid solution is titrated with 0.35 M NaOH. The initial buret reading is 0.23 mL. The phenolphthalein indicator turns the solution light pink when the buret reads 29.58 mL.
B. How many moles of NaOH were delivered?
C. How many Moles of weak acid were present in the solution?
D. Calculate the molarity of the unknown weak acid solution
I answered this earlier, at least partially. See your other posts and help me understand what you don't. Explain in detail.
To find the answers to these questions, we need to use the concept of stoichiometry and the balanced chemical equation for the reaction between the acid and the base. Let's break down the steps:
Step 1: Convert the initial and final buret readings into volume of NaOH used during the titration.
- Initial buret reading: 0.23 mL
- Final buret reading: 29.58 mL
- Volume of NaOH used: Final buret reading - Initial buret reading
Step 2: Convert the volume of NaOH used into moles of NaOH.
- Moles of NaOH = Volume of NaOH used (in L) x Molarity of NaOH
Step 3: Determine the mole ratio between NaOH and the weak acid using the balanced chemical equation for the reaction.
- Balanced chemical equation: Acid + NaOH = Salt + Water
- In a 1:1 ratio, 1 mole of acid reacts with 1 mole of NaOH.
Step 4: Calculate the moles of the weak acid.
- Moles of weak acid = Moles of NaOH
Step 5: Calculate the molarity of the weak acid solution.
- Molarity of the weak acid solution = Moles of weak acid / Volume of weak acid solution (in L)
Let's now apply these steps to find the answers:
B. How many moles of NaOH were delivered?
Step 1: Volume of NaOH used = 29.58 mL - 0.23 mL = 29.35 mL = 0.02935 L
Step 2: Moles of NaOH = 0.02935 L x 0.35 mol/L (given molarity) = 0.01025 mol
C. How many moles of weak acid were present in the solution?
Step 3: Since the balanced chemical equation is 1:1, the moles of the weak acid present are also 0.01025 mol.
D. Calculate the molarity of the unknown weak acid solution.
Step 4: Molarity of the acid solution = Moles of weak acid / Volume of weak acid solution
= 0.01025 mol / 0.01500 L (given volume of the weak acid solution)
= 0.6833 mol/L (rounded to four decimal places)
Therefore, the molarity of the unknown weak acid solution is 0.6833 mol/L.