A student weights 1.700 g of succinic acid and dissolves it in water in a 250.0 mL volumetric flask. A 25.00 mL sample of this solution is withdrawn and placed in a 125 mL Erlenmeyer flask, to which 5 drops of the acid-base indicator phenolphthalein is added. This solution is titrated with a sodium hydroxide solution of unknown molarity in a buret.
a) How many moles of succinic acid were placed in the Erlenmeyer flask?
b) If the unknown sodium hydroxide solution was known to be approximately 0.20 M, at approximately what buret volume would you expect the end point of the titration?
c) If the measured volume at the end point was 13.32 mL of sodium hydroxide added, calculate the actual molarity of the sodium hydroxide solution.
A. mols succinic acid in the initial 1.700 g is mols = grams/molar mass = ?
Then you took 1/10 of that with
?mols x (25.00 mL/250.00 mL) = ?
B. If we call succinic acid H2C, then
H2C + 2NaOH ==> Na2C + 2H2O
mols succinic acid from a = ?
2x that = mols NaOH
M NaOH = mols NaOH/L NaOH. Solve for L NaOH and convert to mL
C. See B above.
a) To determine the number of moles of succinic acid placed in the Erlenmeyer flask, we can use the molar mass of succinic acid. The molecular formula of succinic acid is C4H6O4, so its molar mass is:
(4 * atomic mass of carbon) + (6 * atomic mass of hydrogen) + (4 * atomic mass of oxygen)
= (4 * 12.01 g/mol) + (6 * 1.01 g/mol) + (4 * 16.00 g/mol)
= 118.09 g/mol
Since the student weighed 1.700 g of succinic acid and the molar mass is 118.09 g/mol, we can calculate the number of moles as:
moles = mass / molar mass
moles = 1.700 g / 118.09 g/mol
moles ≈ 0.0144 mol
Therefore, approximately 0.0144 moles of succinic acid were placed in the Erlenmeyer flask.
b) To determine the approximate buret volume at the end point of the titration, we need to use the stoichiometry of the reaction between succinic acid and sodium hydroxide.
From the balanced chemical equation of the reaction:
C4H6O4 + 2NaOH → Na2C4H4O4 + 2H2O
we can see that each mole of succinic acid reacts with 2 moles of sodium hydroxide.
Since the molar ratio is 2:1, the number of moles of sodium hydroxide used in the reaction will be half the number of moles of succinic acid used.
So, moles of sodium hydroxide used = 0.0144 mol / 2 = 0.0072 mol
The concentration of the sodium hydroxide solution is given as approximately 0.20 M, which means for every 1 liter of the solution, there are 0.20 moles of sodium hydroxide.
Since the buret volume represents the volume of sodium hydroxide solution used, we can calculate the approximate buret volume at the end point as:
buret volume = moles of sodium hydroxide used / molarity
buret volume ≈ 0.0072 mol / 0.20 mol/L
buret volume ≈ 0.036 L = 36 mL
Therefore, we would expect the end point of the titration to be at approximately 36 mL in the buret.
c) From the given information, the measured volume at the end point is reported as 13.32 mL of sodium hydroxide added.
Using this information, we can calculate the actual molarity of the sodium hydroxide solution.
buret volume = 13.32 mL = 0.01332 L
moles of sodium hydroxide used = buret volume * molarity
0.0072 mol = 0.01332 L * molarity
Solving for molarity:
molarity = 0.0072 mol / 0.01332 L
molarity ≈ 0.542 M
Therefore, the actual molarity of the sodium hydroxide solution is approximately 0.542 M.
a) To find the number of moles of succinic acid in the Erlenmeyer flask, we need to first calculate the number of moles of succinic acid in the volumetric flask.
The molar mass of succinic acid (C4H6O4) is:
Molar mass = (4 * atomic mass of carbon) + (6 * atomic mass of hydrogen) + (4 * atomic mass of oxygen)
= (4 * 12.011 g/mol) + (6 * 1.008 g/mol) + (4 * 16.00 g/mol)
= 116.09 g/mol
Given that the student weighed 1.700 g of succinic acid, we can calculate the number of moles using the formula:
Number of moles = Mass / Molar mass
= 1.700 g / 116.09 g/mol
≈ 0.0146 mol
Therefore, there are approximately 0.0146 moles of succinic acid in the Erlenmeyer flask.
b) To estimate the buret volume at the end point of the titration, we can use the stoichiometry of the reaction between succinic acid and sodium hydroxide.
The balanced chemical equation for the reaction is:
C4H6O4 + 2NaOH → C4H4O4 + 2H2O + 2Na+
From the equation, we can see that each mole of succinic acid reacts with 2 moles of sodium hydroxide. Therefore, the number of moles of sodium hydroxide required to neutralize 0.0146 moles of succinic acid will be 2 times that amount, which is 0.0292 moles.
Given that the concentration of the sodium hydroxide solution is approximately 0.20 M, we can calculate the volume of sodium hydroxide solution needed to reach the end point using the formula:
Volume (L) = Moles / Concentration
= 0.0292 mol / 0.20 mol/L
= 0.146 L
To convert the volume to mL, we multiply by 1000:
Volume (mL) = 0.146 L * 1000 mL/L
= 146 mL
Therefore, at approximately 146 mL of sodium hydroxide solution in the buret, we would expect to reach the end point of the titration.
c) To calculate the actual molarity of the sodium hydroxide solution, we can use the information given in the question.
The volume of sodium hydroxide solution at the end point is given as 13.32 mL.
Using the equation Moles = Concentration * Volume, we can calculate the moles of sodium hydroxide added:
Moles = 0.20 M * 13.32 mL
= 2.664 mmol
Since we know that 1 mole of sodium hydroxide reacts with 1 mole of succinic acid, the moles of sodium hydroxide added are equal to the moles of succinic acid in the Erlenmeyer flask: 0.0292 mol.
Now we can calculate the actual molarity of the sodium hydroxide solution using the formula:
Molarity = Moles / Volume
= 0.0292 mol / 0.01332 L
= 2.196 M
Therefore, the actual molarity of the sodium hydroxide solution is approximately 2.196 M.