Question

При взаимодействии фенола с бромной водой образуется нерастворимый в воде 2,4,6-трибромфенол (качественная реакция на фенол). При действии избытка бромной воды на 240г водного раствора фенола получено 8,45г осадка. Рассчитайте массовую долю фенола в исходном растворе.

Answer 1

Количество вещества трибромфенола (C6H2Br3OH): 8,45 / 331 = 0,0255 моль фенола было 0,0255 х 94 = 2,4 грамма массовая доля фенола в растворе: (2,4 / 240) х 100% = 1%=)))

Answer 2

Reaction between Phenol and Bromine Water

When phenol reacts with bromine water (aqueous solution of bromine), it forms insoluble 2,4,6-tribromophenol. This reaction is a qualitative test for phenol.

Calculation of the Mass Fraction of Phenol in the Initial Solution

To calculate the mass fraction of phenol in the initial solution, we need to use the given information. It states that when an excess of bromine water reacts with a 240g aqueous solution of phenol, 8.45g of precipitate is obtained.

Let's assume the mass of phenol in the initial solution is "x" grams.

According to the reaction, 1 mole of phenol reacts with 3 moles of bromine to form 1 mole of 2,4,6-tribromophenol. The molar mass of phenol is 94.11 g/mol, and the molar mass of 2,4,6-tribromophenol is 329.77 g/mol.

From the given information, we can set up the following equation based on the molar ratios:

(8.45 g 2,4,6-tribromophenol) / (329.77 g/mol 2,4,6-tribromophenol) = (x g phenol) / (94.11 g/mol phenol)

Simplifying the equation, we can solve for "x" to find the mass of phenol in the initial solution:

x = (8.45 g 2,4,6-tribromophenol) / (329.77 g/mol 2,4,6-tribromophenol) * (94.11 g/mol phenol)

Calculating this expression, we find:

x ≈ 2.42 g

Therefore, the mass of phenol in the initial solution is approximately 2.42 grams.

Mass Fraction Calculation

To calculate the mass fraction of phenol in the initial solution, we divide the mass of phenol by the total mass of the solution and multiply by 100%.

Mass fraction of phenol = (mass of phenol / total mass of solution) * 100%

Given that the total mass of the solution is 240 grams, we can calculate the mass fraction:

Mass fraction of phenol = (2.42 g / 240 g) * 100%

Calculating this expression, we find:

Mass fraction of phenol ≈ 1.01%

Therefore, the mass fraction of phenol in the initial solution is approximately 1.01%.