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 1.894 g;
buret reading before titration 0.13 mL; buret
reading after titration 32.57 mL.
Answer in units of M.
moles KHP = grams/molar mass
Substitute and solve for mols.
KHP + NaOH ==> NaHP + H2O
so the reaction is 1:1 and moles KHP = moles NaOH.
Then M NaOH = moles NaOH/L NaOH.
To obtain L NaOH, you will need to subtract the final buret reading - initial buret reading and convert to L.
Do I use the molar mass of just KHP or with H2O as well?
mols of solute therefore just KHP
To calculate the molarity of the NaOH (sodium hydroxide) solution, we'll use the concept of stoichiometry. We know that sodium hydroxide reacts with potassium hydrogen phthalate (KHP) in a 1:1 ratio, meaning that one mole of NaOH reacts with one mole of KHP.
Here's how we can calculate the molarity of the NaOH solution step by step:
1. Calculate the number of moles of KHP used in the titration:
The molar mass of KHP is given as 204.2 g/mol.
Moles of KHP = Mass of KHP used / Molar mass of KHP
Moles of KHP = 1.894 g / 204.2 g/mol
2. Determine the volume of NaOH used in the titration:
Volume of NaOH used = Buret reading after titration - Buret reading before titration
Volume of NaOH used = 32.57 mL - 0.13 mL
Convert this volume to liters by dividing by 1000: Volume of NaOH used = (32.57 mL - 0.13 mL) / 1000 L/mL
3. Calculate the molarity of the NaOH solution:
Molarity = Moles of NaOH / Volume of NaOH used
The moles of NaOH and KHP are equal based on the balanced equation, so we can use the moles of KHP from step 1.
Molarity = Moles of KHP / Volume of NaOH used
Finally, substitute the values into the equation:
Molarity = (1.894 g / 204.2 g/mol) / [(32.57 mL - 0.13 mL) / 1000 L/mL]
Now, let's calculate the molarity using the given data:
Molarity = (1.894 g / 204.2 g/mol) / [(32.57 mL - 0.13 mL) / 1000 L/mL]
Molarity = 0.008786 mol / 0.03257 L
Molarity ≈ 0.269 M
Therefore, the molarity of the NaOH solution is approximately 0.269 M.