An analytical chemist weighs out 0.115g of an unknown monoprotic acid into a 250mL volumetric flask and dilutes to the mark with distilled water. She then titrates this solution with 0.0700M NaOH solution. When the titration reaches the equivalence point, the chemist finds she has added 21.6mL of NaOH solution.Calculate the molar mass of the unknown acid. Round your answer to 3 significant digits.
Question
An analytical chemist weighs out 0.115g of an unknown monoprotic acid into a 250mL volumetric flask and dilutes to the mark with distilled water. She then titrates this solution with 0.0700M NaOH solution. When the titration reaches the equivalence point, the chemist finds she has added 21.6mL of NaOH solution.Calculate the molar mass of the unknown acid. Round your answer to 3 significant digits.
Solution 1
To calculate the molar mass of the unknown acid, we need to follow these steps:
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First, we need to calculate the moles of NaOH used in the titration. We can do this using the formula: moles = concentration * volume. The concentration of NaOH is given as 0.0700 M and the volume is given as 21.6 mL (which we need to convert to L by dividing by 1000), so:
moles of NaOH = 0.0700 M * 21.6 mL / 1000 = 0.001512 mol
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Since the unknown acid is monoprotic, it means that one mole of the acid reacts with one mole of NaOH. Therefore, the moles of the unknown acid is also 0.001512 mol.
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Now, we can calculate the molar mass of the unknown acid using the formula: molar mass = mass / moles. The mass of the acid is given as 0.115 g and we've calculated the moles as 0.001512 mol, so:
molar mass of the unknown acid = 0.115 g / 0.001512 mol = 75.926 g/mol
So, the molar mass of the unknown acid is approximately 75.9 g/mol when rounded to three significant digits.
Solution 2
To calculate the molar mass of the unknown acid, we need to follow these steps:
-
First, we need to calculate the moles of NaOH used in the titration. We can do this using the formula: moles = concentration * volume. The concentration of NaOH is given as 0.0700 M and the volume is given as 21.6 mL (which we need to convert to L by dividing by 1000), so:
moles of NaOH = 0.0700 M * 21.6 mL / 1000 = 0.001512 mol
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Since the unknown acid is monoprotic, it means that one mole of the acid reacts with one mole of NaOH. Therefore, the moles of the unknown acid is also 0.001512 mol.
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Now, we can calculate the molar mass of the unknown acid using the formula: molar mass = mass / moles. The mass of the acid is given as 0.115 g, so:
molar mass of the unknown acid = 0.115 g / 0.001512 mol = 75.926 g/mol
So, the molar mass of the unknown acid is approximately 75.9 g/mol when rounded to three significant digits.
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