A flask contains 0.342 g of acid and a few drops of phenolphthalein indicator dissolved in water. The buret contains 0.120 M NaOH. 20.f mL of base is needed to reach the endpoint of the titration.
Assuming that the acid is monoprotic, what is the molar mass?
To determine the molar mass of the acid, you will need to use the concept of titration and stoichiometry. Here's how you can approach this problem:
1. Write the balanced chemical equation for the reaction between the acid and the base. Since the acid is assumed to be monoprotic, the equation can be written as follows:
Acid (AH) + NaOH → NaA + H2O
2. Determine the moles of NaOH used in the titration. The volume of NaOH used is given as 20.0 mL, and the molarity of NaOH is 0.120 M. Using the formula:
Moles of NaOH = Volume (L) x Molarity (mol/L)
Convert the volume given in milliliters to liters:
Volume (L) = 20.0 mL / 1000 = 0.020 L
Now, calculate the moles of NaOH used:
Moles of NaOH = 0.020 L x 0.120 mol/L
3. Apply stoichiometry to find the moles of acid required to react with NaOH. From the balanced equation, you can see that one mole of acid reacts with one mole of NaOH. Thus:
Moles of Acid = Moles of NaOH
4. Determine the molar mass of the acid using the given mass of the acid and the calculated moles of acid. The mass of the acid is given as 0.342 g:
Molar Mass of Acid (g/mol) = Mass of Acid (g) / Moles of Acid
Substitute the values:
Molar Mass of Acid = 0.342 g / Moles of Acid
By following this process, you can find the molar mass of the acid.