a solution of sodium hydroxide is standardized against potassium hydrogen phthalate (KHP, formula weight 204.2 g/mol). From the following data, calculate the molarity of the NaOH solution: mass of KHP 1.054 g; buret reading before tiltration 0.33 mL; buret reading after tiltration 36.37 mL.
Answer in units of M.
moles KHP = grams/molar mass.
moles NaOH = moles KHP (write the equation to see that it is a 1:1 ratio).
M NaOH = moles NaOH/L.
Yo will need to subtract the final buret reading from the initial buret reading to obtain the total mL NaOH used, then convert to L to substitute into M = mols/L.
To calculate the molarity (M) of the NaOH solution, we need to determine the number of moles of KHP used in the titration and use it to find the number of moles of NaOH. Then, we can divide the moles of NaOH by the volume of NaOH solution used in the titration to find the molarity.
First, calculate the number of moles of KHP used:
- The formula weight of KHP is given as 204.2 g/mol.
- The mass of KHP used in the titration is given as 1.054 g.
- Use the equation: Moles = mass / formula weight
Moles of KHP = 1.054 g / 204.2 g/mol
Next, we need to calculate the moles of NaOH used in the titration.
- The balanced chemical equation for the reaction of NaOH and KHP is:
NaOH + KHP → NaKP + H2O
- The stoichiometry of the reaction tells us that 1 mole of NaOH reacts with 1 mole of KHP.
- Since the reaction is 1:1, the number of moles of NaOH is the same as the moles of KHP used.
Now we have the moles of NaOH used in the titration. To find the molarity, we need to divide the moles of NaOH by the volume of NaOH solution used.
- The volume of NaOH solution used in the titration is the difference between the initial and final buret readings, i.e., 36.37 mL - 0.33 mL.
- Convert the volume to liters by dividing by 1000: (36.37 mL - 0.33 mL) / 1000.
Finally, divide the moles of NaOH by the volume of solution used to get the molarity:
Molarity of NaOH = Moles of NaOH / Volume of NaOH solution.
Now, let's substitute the values into the equation to calculate the molarity:
Moles of KHP = 1.054 g / 204.2 g/mol = 0.00516 mol
Volume of NaOH solution = (36.37 mL - 0.33 mL) / 1000 = 0.03604 L
Molarity of NaOH = 0.00516 mol / 0.03604 L
Molarity of NaOH ≈ 0.143 M (rounded to three decimal places)
Therefore, the molarity of the NaOH solution is approximately 0.143 M.