your lab possesses a stock solution of NaOH whose concentration is approx. 0.1M. you prepare a secondary solution by diluting 15.00mL of this stock solution to a total volume of 250.0 mL. you titrate a 50.00mL aliquot of the secondary solution with a hydrochloric acid solution that is 0.0252M. the initial burette reading is 12.38mL and the final burrette reading (at the equivalence point) is 25.01mL. Express the derived concentration of the stock solution.
mL used = 25.01-12.38 = 12.63 mL of 0.0252M HCl.
mols HCl = 0.0252 x 0.01238 = about 0.00031 (but you need to be more careful with these numbers)
You titrated 50 mL of the diluted NaOH; therefore, the M of the titrated solution is
0.00031/0.050L = about 0.0062M
That solution came from the stock solution that was diluted 15 to 250 mL; therefore, 0.00624 x 250/15 = about 0.104M for the stock solution.
To find the concentration of the stock solution, we can use the concept of stoichiometry and the data provided in the question.
Let's go step by step to solve this problem:
Step 1: Determine the volume of hydrochloric acid (HCl) used in the titration.
- Initial burette reading: 12.38 mL
- Final burette reading: 25.01 mL
Volume of HCl used = Final burette reading - Initial burette reading
= 25.01 mL - 12.38 mL
= 12.63 mL
Step 2: Convert the volume of HCl used to liters.
Volume of HCl used = 12.63 mL = 0.01263 L
Step 3: Use the stoichiometry of the balanced equation to find the moles of NaOH used.
The balanced equation for the reaction between NaOH and HCl is:
NaOH + HCl -> NaCl + H2O
From the equation, we know that 1 mole of NaOH reacts with 1 mole of HCl.
Therefore, moles of NaOH used = moles of HCl used
Step 4: Calculate the moles of HCl used.
Moles of HCl = Molarity of HCl * Volume of HCl used
= 0.0252 M * 0.01263 L
Step 5: Calculate the moles of NaOH used.
Moles of NaOH used = Moles of HCl used
Step 6: Determine the volume of the secondary solution used in the titration.
Volume of the secondary solution used = 50.00 mL = 0.05000 L
Step 7: Calculate the concentration of the secondary solution.
Concentration of the secondary solution = Moles of NaOH used / Volume of the secondary solution used
= Moles of NaOH used / 0.05000 L
Step 8: Calculate the concentration of the stock solution.
Since the volume of stock solution used was 15.00 mL, we can use the equation:
Concentration of the stock solution * Volume of the stock solution = Concentration of the secondary solution * Volume of the secondary solution used
Concentration of the stock solution = (Concentration of the secondary solution * Volume of the secondary solution used) / Volume of the stock solution used
Concentration of the stock solution = (Concentration of the secondary solution * 0.05000 L) / 0.01500 L
Now, you can plug in the values to calculate the concentration of the stock solution.