A solution of sodium hydroxide is standard-
ized 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 1.654 g;
buret reading before titration 0.23 mL; buret
reading after titration 47.07 mL.
Answer in units of M
KHP + NaOH ==> NaKP + H2O
So 1 mole KHP uses 1 mole NaOH.
moles KHP = grams/molar mass. Calculate moles KHP
Then moles NaOH = moles KHP
M NaOH = moles NaOH/L NaOH.
(mL NaOH used = final reading - initial reading, then convert to liters.)
To calculate the molarity (M) of the NaOH solution, you need to use the formula:
Molarity (M) = (moles of KHP)/(volume of NaOH solution in liters)
First, you need to calculate the moles of KHP used in the titration. To do this, follow these steps:
1. Calculate the moles of KHP using its formula weight (204.2 g/mol) and the mass of KHP used (1.654 g):
Moles of KHP = (mass of KHP)/(formula weight of KHP)
Moles of KHP = 1.654 g / 204.2 g/mol
2. Convert the volume of NaOH solution used in the titration from milliliters (mL) to liters (L):
Volume of NaOH solution used = Buret reading after titration - Buret reading before titration
Volume of NaOH solution used = 47.07 mL - 0.23 mL
Volume of NaOH solution used = 46.84 mL (or 0.04684 L)
Now, you can substitute these values into the formula above to calculate the molarity of the NaOH solution:
Molarity (M) = (moles of KHP)/(volume of NaOH solution in liters)
Molarity (M) = (1.654 g / 204.2 g/mol) / 0.04684 L
Molarity (M) ≈ 0.3777 M
Therefore, the molarity of the NaOH solution is approximately 0.3777 M.