Given 20g of benzoic acid contaminated with 0.4g of salicytic acid.
1)Determine the volume of hot water required to dissolve the mass of acid.
2)Calculate the mass of benzoic acid which participates when the solution is cooled to 20°C. Deduce.
3)Calculate the mass of salicylic acid which co-precipitated with the mass of benzoic acid.
Solubility(g/100ml)
At 20°C : Benzoic acid: 0.29
Salicylic acid: 0.22
At 100°C: Benzoic acid: 6.8
Salicytic acid: 6.67
Answer this question
To solve this problem, we need to use the solubility information provided. Here's how we can tackle each question step-by-step:
1) Determine the volume of hot water required to dissolve the mass of acid.
- We know that the solubility of benzoic acid at 100°C is 6.8g/100ml.
- Therefore, we can calculate the volume of hot water required using the following equation:
Volume of hot water = (Mass of benzoic acid + Mass of salicytic acid) / Solubility of benzoic acid at 100°C
Mass of benzoic acid = 20g - 0.4g (contaminant) = 19.6g
Volume of hot water = (19.6g + 0.4g) / 6.8g/100ml
2) Calculate the mass of benzoic acid which participates when the solution is cooled to 20°C. Deduce.
- We can calculate the mass of benzoic acid that will crystallize or precipitate out of the solution when cooled using the solubility at 20°C.
- The solubility of benzoic acid at 20°C is 0.29g/100ml.
- Therefore, the mass of benzoic acid precipitated can be calculated as:
Mass of benzoic acid = Solubility of benzoic acid at 20°C * Volume of hot water used
3) Calculate the mass of salicylic acid which co-precipitated with the mass of benzoic acid.
- The mass of salicylic acid that co-precipitates with the benzoic acid can be calculated as the difference between the initial mass of salicylic acid and the remaining mass of salicylic acid in the solution after benzoic acid precipitation.
- The initial mass of salicylic acid is given as 0.4g.
- The remaining mass of salicylic acid in the solution can be calculated as:
Remaining mass of salicylic acid = Initial mass of salicylic acid - (Volume of hot water used * Solubility of salicylic acid at 20°C)
Mass of salicylic acid co-precipitated = Initial mass of salicylic acid - Remaining mass of salicylic acid
Note: All calculations will be done using the provided solubility values and the equations mentioned above.
To answer these questions, we need to consider the solubilities of benzoic acid and salicylic acid at different temperatures and use the information about the contaminated mixture to calculate the desired quantities.
1) Determine the volume of hot water required to dissolve the mass of acid:
To find the volume of hot water needed to dissolve the mass of acid, we need to know the solubility of benzoic acid at the given temperature. From the given solubility data, we can see that at 100°C, the solubility of benzoic acid is 6.8g/100ml.
So, to dissolve 20g of benzoic acid, we can set up a proportion:
20g benzoic acid / x ml water = 6.8g solubility / 100ml water
Cross-multiplying and solving for x:
20g * 100ml water = 6.8g * x ml water
2000 = 6.8x
x ≈ 294.1 ml
Therefore, approximately 294.1 ml of hot water is required to dissolve the 20g of benzoic acid.
2) Calculate the mass of benzoic acid that participates when the solution is cooled to 20°C:
To determine the mass of benzoic acid that participates when the solution is cooled to 20°C, we can calculate the maximum amount of benzoic acid that can remain dissolved at this temperature.
Given that the solubility of benzoic acid at 20°C is 0.29g/100ml, we can set up the proportion:
0.29g benzoic acid / 100ml water = x g benzoic acid / 294.1 ml water
Cross-multiplying and solving for x:
0.29g * 294.1 ml water = 100ml water * x g benzoic acid
x ≈ 0.852g
Hence, approximately 0.852g of benzoic acid would participate when the solution is cooled to 20°C.
Deduction: The calculated mass of benzoic acid, 0.852g, is the amount left in the solution after cooling. The remaining mass is the amount that precipitates out of the solution.
3) Calculate the mass of salicylic acid that co-precipitates with the mass of benzoic acid:
To find the mass of salicylic acid that co-precipitates with the benzoic acid, we need to subtract the mass of benzoic acid from the total contamination.
Total contamination = Mass of benzoic acid + Mass of salicylic acid
Total contamination = 20g + 0.4g
Total contamination = 20.4g
Since we determined that approximately 0.852g of benzoic acid participates, the remaining contamination is due to salicylic acid:
Salicylic acid contamination = Total contamination - Mass of benzoic acid
Salicylic acid contamination = 20.4g - 0.852g
Salicylic acid contamination ≈ 19.548g
Therefore, approximately 19.548g of salicylic acid co-precipitated with the mass of benzoic acid.