A student tried to dissolve 5.0 grams of impure acetanilide in 50 Ml of hot water. However was not able to get it to dissolve. Why not?
What would you do to get it to dissolve??
Acetanilide is much less soluble in water than this, about 1g per 200 ml of cold water.
There are a couple of ways to get it to dissolve, depending on why it needs to be dissolved.
If the intention is to recrystalise it then heating the water will help dissolve the sample.
If a cold water solution is needed then more water needs to be added.
If a solution is needed, but the volume needs to be kept to a minimum then add methanol (or acetone) dropwise to the suspension in 50 ml until it dissolves.
The impure acetanilide may not have dissolved in the hot water for several reasons. One reason could be that the impurities present in the acetanilide affected its solubility. Additionally, the temperature might not have been high enough to dissolve the impure acetanilide completely. Another possibility is that the amount of water used was not sufficient to dissolve the impurities.
To get the impure acetanilide to dissolve, there are a few steps you can follow:
1. Increase the temperature: Higher temperatures typically increase the solubility of solids in liquids. Ensure that the water is heated to the maximum temperature possible without causing any hazardous situations.
2. Increase the surface area: Grinding or crushing the impure acetanilide into smaller particles will increase its surface area. This exposes more of the acetanilide to the water, making it easier for it to dissolve.
3. Add more solvent: Increase the amount of water used in the solution. This will provide more medium for the impurities to dissolve into.
4. Stir the solution: Agitating the mixture, either manually or using a stirrer, helps to enhance the contact between the impurities and the solvent, promoting dissolution.
By following these steps, you should be able to increase the chances of dissolving the impure acetanilide in hot water. However, keep in mind that some impurities might be insoluble or may require additional purification techniques.