A sample contains an unknown amount of tartaric acid, H2C4H4O6. If 0.3888 g of the sample
requires 37.74 mL of 0.1000 M NaOH to neutralize the H2C4H4O6 completely, what is the percentage of
H2C4H4O6 in the sample? The molar mass of H2C4H4O6 is 150.09 g/mol. The balanced equation for the
reaction is:
H2C4H4O6 + 2 NaOH → 2 H2O + Na2C4H4O6
So i got 72.84
You have 0.6559 g of an unknown monoprotic acid, HA, which reacts with NaOH according to the
balanced equation
HA + NaOH → NaA + H2O
If 36.67 mL of 0.0934 M NaOH is required to titrate the acid to the equivalence point, what is the molar
mass of the acid?
I got 190.5
Am I right? Appreciate any help
72.84 yes
190.5 no but close.
191.5?
yes
To determine whether your answers are correct, let's go through the calculations step by step.
For the first question:
1. Calculate the number of moles of NaOH used:
moles of NaOH = volume of NaOH (in L) x concentration of NaOH (in mol/L)
moles of NaOH = 37.74 mL / 1000 mL/L x 0.1000 mol/L = 0.003774 mol
2. Use the balanced equation to relate the moles of NaOH to the moles of tartaric acid (H2C4H4O6):
According to the equation, 1 mole of tartaric acid reacts with 2 moles of NaOH.
So, moles of H2C4H4O6 = (0.003774 mol NaOH) / 2 = 0.001887 mol
3. Calculate the mass of H2C4H4O6:
mass of H2C4H4O6 = moles of H2C4H4O6 x molar mass of H2C4H4O6
mass of H2C4H4O6 = 0.001887 mol x 150.09 g/mol = 0.283 g
4. Calculate the percentage of H2C4H4O6 in the sample:
percentage of H2C4H4O6 = (mass of H2C4H4O6 / mass of sample) x 100
percentage of H2C4H4O6 = (0.283 g / 0.3888 g) x 100 = 72.84%
So, your answer of 72.84% for the first question is correct.
Now, let's move on to the second question:
1. Calculate the number of moles of NaOH used:
moles of NaOH = volume of NaOH (in L) x concentration of NaOH (in mol/L)
moles of NaOH = 36.67 mL / 1000 mL/L x 0.0934 mol/L = 0.003428 mol
2. Use the balanced equation to relate the moles of NaOH to the moles of HA:
According to the equation, 1 mole of HA reacts with 1 mole of NaOH.
So, moles of HA = 0.003428 mol
3. Calculate the molar mass of HA:
molar mass of HA = mass of HA / moles of HA
molar mass of HA = 0.6559 g / 0.003428 mol = 191.2 g/mol (rounded to one decimal place)
Therefore, your answer of 190.5 g/mol for the molar mass of the acid is incorrect. The correct molar mass of the acid should be 191.2 g/mol (rounded to one decimal place).
I hope this helps! Let me know if you have any other questions.