Question

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sechon, freezing temperature for the benzoic acid-lauric acid mixture. tuhe thhter the temperatures shown in either examine box should be equal to the DATA AND CALCULATIONS Mass of lauric acid Mass of benzoic acid Freezing temperature of pure lauric acid Freezing point of the benzoic acid-lauric acid mixture Freezing temperature depression, At 9 6 eC °C Molality. m KA Moles of benzoic acid mol Molecular weight of benzoic acid (experimental) Molecular weight of benzoic acid (accepted) g/mol Percent error Chemistry with Computers 15-4

Answer 1

In the problem, given datas are:

Mass of Lauric Acid(Solvent) = 8.05 g

Mass of Benzoic Acid(Solute) = 1.01 g

Freezing point of pure solvent i.e. Lauric Acid = 43.5 C

Freezing point of Benzoic Acid- Lauric Acid Mixture = 40.4 C

Hence, Depression in freezing point of Lauric Acid on Mixing Benzoic Acid = 43.5-40.4 C = 3.1 C

Theoretical Molecular Mass of Benzoic Acid (C6H5COOH) is 122 g

Let us assume the experimental Molecular weight of Benzoic Acid is M g

The remaining calculations to find all the missing information is in the following image:

In the problem, given datas are: Mass of Lauric Acid(Solvent) = 8.05 g Mass of Benzoic Acid(Solute) = 1.01 g Freezing point of pure solvent i.e. Lauric Acid = 43.5 C Freezing point of Benzoic Acid- Lauric Acid Mixture = 40.4 C Hence, Depression in freezing point of Lauric Acid on Mixing Benzoic Acid = 43.5-40.4 C = 3.1 C Theoretical Molecular Mass of Benzoic Acid (C6H5COOH) is 122 g Let us assume the experimental Molecular weight of Benzoic Acid is M g The remaining calculations to find all the missing information is in the following image: if assumed molar mass of Benzoic acid = m g = > moles of Benzoic acid = (w/m) = (1.01/m) moles = > molality of Benzoic acid - Lauric acid mixture will be: - m = moles of Benzoic Acid/weight of Lauric Acid times 1000 m = 1.01/m times 88.05 times 1000 = (1010/8.05 m) - (1) As per

So as per the calculations:

The Freezing Point depression is 3.1 C

Molarity of Benzoic Acid (Theoretical taking molecular weight of Benzoic Acid 122 g) = 1.027 m

Molarity of Benzoic Acid (Experimental) = 0.795 m

Moles of Benzoic Acid (Theoretical) = 0.00827

Molecular Weight of Benzoic Acid (Experimental) = 157.84 g

Molecular Weight of Benzoic Acid (Theoretical) = 122 g

Percentage Error = 29.38 %