To standardize a solution of NaOH, one uses a primary standard called potassium hydrogen phthalate (KHP). It is a monoprotic acid. It has a molar mass of 204.33g/mol. Suppose you weigh out .556g of KHP and dissolve it in water. It requires 14.48 mL of NaOH to reach the endpoint. What is the concentration of the NaOH solution?
mols KHP = grams/molar mass = ?
mols NaOH = mols KHP
M NaOH = mols NaOH/L NaOH
To determine the concentration of the NaOH solution, we can use the concept of stoichiometry and the equation for the reaction between NaOH and KHP.
The balanced equation for the reaction is:
NaOH + KHP → NaKP + H2O
From the balanced equation, we can determine the mole ratio between NaOH and KHP, which is 1:1.
Step 1: Calculate the number of moles of KHP (potassium hydrogen phthalate):
Molar mass of KHP = 204.33 g/mol
Mass of KHP used = 0.556 g
Number of moles of KHP = Mass of KHP used / Molar mass of KHP
Number of moles of KHP = 0.556 g / 204.33 g/mol
Step 2: Calculate the concentration of NaOH:
Volume of NaOH used = 14.48 mL = 0.01448 L (since 1 mL = 0.001 L)
Using the mole ratio from the balanced equation (1:1), we can say that the number of moles of NaOH is equal to the number of moles of KHP.
Number of moles of NaOH = Number of moles of KHP
Step 3: Calculate the concentration of NaOH:
Concentration of NaOH = Number of moles of NaOH / Volume of NaOH used
Concentration of NaOH = Number of moles of KHP / Volume of NaOH used
Concentration of NaOH = (0.556 g / 204.33 g/mol) / 0.01448 L
Step 4: Calculate the final concentration of NaOH solution in units of Molarity (M):
Concentration of NaOH (M) = Concentration of NaOH (mol/L)
Concentration of NaOH (M) = [(0.556 g / 204.33 g/mol) / 0.01448 L] mol/L
Calculate the result to find the concentration of the NaOH solution.
To find the concentration of the NaOH solution, we can first start by calculating the number of moles of KHP used in the reaction.
1. Calculate the number of moles of KHP:
- Molar mass of KHP = 204.33 g/mol
- Mass of KHP used = 0.556 g
- Number of moles of KHP = mass / molar mass
= 0.556 g / 204.33 g/mol
Next, we need to determine the molar ratio between KHP and NaOH. From the balanced chemical equation:
KHP + NaOH → KNaP + H2O
we can see that the ratio is 1:1.
Since we know the number of moles of KHP used, the number of moles of NaOH required to react with the KHP will also be the same.
Thus, the number of moles of NaOH = 0.556 moles
Finally, we can calculate the concentration of the NaOH solution.
2. Calculate the concentration of NaOH:
- Volume of NaOH used = 14.48 mL (convert to L by dividing by 1000)
- Concentration = number of moles / volume in liters
= 0.556 moles / 0.01448 L
Now, divide the number of moles by the volume in liters to get the concentration of NaOH.
The concentration of the NaOH solution is approximately:
Concentration = 0.556 moles / 0.01448 L = 38.37 mol/L
Therefore, the concentration of the NaOH solution is approximately 38.37 mol/L.