A solution made by mixing 95.00 mL of 0.950 M HCOOH with 35.00 mL of 0.750 M NaOH.
what about it?
Using tabulated Ka and Kb values, calculate the pH of the following solutions.
millimoles HCOOH = mL x M = 95.00 mL x 0.950 M = 90.25
millimols NaOH = 35.00 mL x 0.750 = 26.25
................HCOOOH + NaOH ==> HCOONa + H2O
Initial............90.25...........0.................0................
add..............................26.25........................................
change.........-26.25.....026.25............+26,25
equilibrium.... 64.00.........0...................26.25
Total volume = 95.00 + 35.00 = 130 mL.
This should be obvious you have a buffered solution of HCOOH and NaOOCH
From the equilibrium line you have
(HCOOH) = millimoles/mL = ? = acid
(HCOONa) = millimoles/mL = ? = base
Substitute into Henserson-Hasselbalch equation which is
pH = pKa + log [(base)/(acid)]
To calculate the resulting solution, we need to use the concept of stoichiometry and the balanced chemical equation of the reaction between HCOOH (formic acid) and NaOH (sodium hydroxide).
The balanced chemical equation for the reaction is:
HCOOH + NaOH → HCOONa + H2O
First, determine the limiting reagent in the reaction by comparing the number of moles of each reactant.
Step 1: Calculate the number of moles of HCOOH:
moles of HCOOH = volume (in liters) × molarity
moles of HCOOH = 0.095 L × 0.950 mol/L
moles of HCOOH = 0.09025 mol
Step 2: Calculate the number of moles of NaOH:
moles of NaOH = volume (in liters) × molarity
moles of NaOH = 0.035 L × 0.750 mol/L
moles of NaOH = 0.02625 mol
Since the stoichiometry of the balanced chemical equation is 1:1, we can conclude that NaOH is the limiting reagent, as it has fewer moles than HCOOH.
Step 3: Calculate the number of moles of HCOONa formed:
moles of HCOONa = moles of limiting reagent (NaOH)
moles of HCOONa = 0.02625 mol
Step 4: Calculate the concentration of HCOONa in the resulting solution:
volume of solution = volume of HCOOH + volume of NaOH
volume of solution = 0.095 L + 0.035 L
volume of solution = 0.130 L
concentration of HCOONa = moles of HCOONa / volume of solution
concentration of HCOONa = 0.02625 mol / 0.130 L
concentration of HCOONa = 0.2019 M
Therefore, the resulting solution has a concentration of 0.2019 M HCOONa.