Vinegar is a dilute solution of acetic acid. In the titration of 5.00 mL of vinegar, 39.75 mL of 0.137 M sodium hydroxide solution was required to neutralize the vinegar to a phenolphthalein end point. Calculate each of the following of the vinegar.
(a) the molarity : I got 1.09 and its correct so im thinking I have to use this for the next part which is
b) the percent by mass (density of solution = 1.007 g/mL)
Thanks:)
You CAN use the answer from part A but it isn't necessary.
moles NaOH = M x L
moles vinegar = moles NaOH
moles = grams vinegar/molar mass vinegar and solve for grams.
Then % acetic acid = (mass acetic acid/mass sample)*100 = ??
You will need to use the density information to convert 5 mL to grams to use for mass of the sample. Vinegar is usually about 4-6% acetic acid.
Thanks!
To calculate the percent by mass of the vinegar, we need to determine the mass of acetic acid in a given volume of vinegar.
(a) Molarity of vinegar:
The molarity of the vinegar can be calculated using the equation:
M1V1 = M2V2
where M1 is the molarity of sodium hydroxide, V1 is the volume of sodium hydroxide solution used, M2 is the molarity of the vinegar (acetic acid), and V2 is the volume of vinegar used.
Given:
M1 = 0.137 M (molarity of sodium hydroxide)
V1 = 39.75 mL (volume of sodium hydroxide solution used)
V2 = 5.00 mL (volume of vinegar used)
Using the equation, we have:
M1V1 = M2V2
(0.137 M)(39.75 mL) = M2(5.00 mL)
M2 = (0.137 M)(39.75 mL) / (5.00 mL) = 1.09925 M
Therefore, the molarity of acetic acid in the vinegar is 1.09925 M.
(b) Percent by mass of acetic acid in vinegar:
To calculate the percent by mass, we need to determine the mass of acetic acid in a given volume of vinegar using its molarity and the density of the solution.
Given:
Density of solution = 1.007 g/mL
Volume of vinegar (V2) = 5.00 mL
Mass of acetic acid = molarity (M2) × volume (V2)
= (1.09925 M)(5.00 mL)
But, the mass is normally expressed in grams, so we need to convert mL to grams using the density of the solution.
Mass of vinegar (solution) = volume (V2) × density
= (5.00 mL)(1.007 g/mL)
Thus, the percent by mass of acetic acid in vinegar can be calculated as follows:
Percent by mass = (Mass of acetic acid / Mass of vinegar) × 100
= [(1.09925 M)(5.00 mL) / (5.00 mL)(1.007 g/mL)] × 100
By simplifying, we get:
Percent by mass = (1.09925 / 1.007) × 100
Percent by mass = 109.074%
Therefore, the percent by mass of acetic acid in vinegar is approximately 109.07%.
To calculate the percent by mass of the vinegar, you first need to calculate the mass of the acetic acid in the solution. Here's how you can do it:
Step 1: Calculate the number of moles of sodium hydroxide used in the titration.
- The volume of the sodium hydroxide solution used is given as 39.75 mL.
- The molarity of the sodium hydroxide solution is given as 0.137 M.
- Use the formula Moles = Molarity x Volume (in liters) to calculate moles of sodium hydroxide:
Moles of NaOH = 0.137 M x (39.75 mL / 1000 mL/ L) = 0.00546 moles
Step 2: Write the balanced equation for the reaction between sodium hydroxide (NaOH) and acetic acid (CH3COOH):
NaOH + CH3COOH → CH3COONa + H2O
Step 3: From the balanced equation, you can see that 1 mole of sodium hydroxide reacts with 1 mole of acetic acid. Therefore, the number of moles of acetic acid in the vinegar solution is also 0.00546 moles.
Step 4: Calculate the mass of acetic acid in grams:
- The molar mass of acetic acid (CH3COOH) is 60.052 g/mol.
- Use the formula Mass = Moles x Molar Mass to calculate the mass of acetic acid:
Mass of acetic acid = 0.00546 moles x 60.052 g/mol = 0.3278 g
Step 5: Calculate the percent by mass.
- The volume of the vinegar used in the titration is given as 5.00 mL.
- The density of the vinegar solution is given as 1.007 g/mL.
- Use the formula Percent by Mass = (Mass of acetic acid / Mass of vinegar) x 100% to calculate:
Percent by Mass = (0.3278 g / (5.00 mL x 1.007 g/mL)) x 100% = 6.527%
So, the percent by mass of acetic acid in the vinegar solution is approximately 6.527%.