What is the pH of the resulting solution if 10.0 mL of 1.0 M NaOH is added to 100 mL of this formic acid - sodium formate solution?
You need to know what "this formic acid-sodium formate solution" is.
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To determine the pH of the resulting solution, you need to first calculate the moles of formic acid and sodium formate present in the solution. Then, you can calculate the concentration of formic acid and sodium formate in the resulting solution. Finally, you can use the concentrations to determine the pH of the solution.
Here's the step-by-step process to get the answer:
Step 1: Calculate the moles of formic acid and sodium formate
- Given that you have 10.0 mL of 1.0 M NaOH, you can calculate the moles of NaOH by multiplying its concentration by the volume in liters: Moles of NaOH = 1.0 M x (10.0 mL / 1000 mL) = 0.01 moles.
- Since NaOH reacts with formic acid in a 1:1 ratio, the moles of NaOH is also equal to the moles of formic acid.
- The sodium formate (NaHCOO) is formed by the reaction between NaOH and formic acid. Therefore, the moles of sodium formate formed will also be equal to 0.01 moles.
Step 2: Calculate the final volume of the solution
- The final volume of the solution will be the sum of the initial volumes of the formic acid - sodium formate solution (100 mL) and the volume of NaOH added (10.0 mL), which gives 110 mL.
Step 3: Calculate the concentrations of formic acid and sodium formate
- To calculate the concentration of formic acid in the resulting solution, divide the moles of formic acid by the final volume in liters: Concentration of formic acid = (0.01 moles) / (110 mL / 1000 mL/L) = 0.091 M.
- To calculate the concentration of sodium formate in the resulting solution, divide the moles of sodium formate by the final volume in liters: Concentration of sodium formate = (0.01 moles) / (110 mL / 1000 mL/L) = 0.091 M.
Step 4: Calculate the pKa of formic acid
- The pKa of formic acid is approximately 3.75.
Step 5: Use the Henderson-Hasselbalch equation to determine the pH
- The Henderson-Hasselbalch equation is: pH = pKa + log ([A-] / [HA])
- In this case, the acid (HA) is formic acid, and the conjugate base (A-) is sodium formate.
- Plug in the values: pH = 3.75 + log (0.091 / 0.091)
- Simplifying the equation, you get: pH = 3.75 + log (1)
- Since the log of 1 is equal to 0, the pH of the resulting solution is equal to the pKa of formic acid, which is 3.75.
Therefore, the pH of the resulting solution is 3.75.