How do we mix water and toluene

This is more a problem with thermal mass. Sulfuric acid releases a lot of thermal energy when water is introduced to typical stock sulfuric acid which is about 90% acid by weight. When dilution is performed, a small mass of the acid is combined with a much larger mass of water.

If the acid mass is in the receiving flask, there is initially a small mass of acid and water as the dilution is started. The energy released will heat up the low mass mixture, with four joules of energy heating up one gram of the mixture by one degree Celsius. If there isn't much mass, then the temperature change is dramatic and can easily cause the solution to boil, throwing droplets of concentrated sulfuric acid in the air.

Sulfuric acid is extremely dangerous. It is intensely hydroscopic and will readily dehydrate carbohydrates and proteins by removing oxygens and hydrogens to make water molecules. This process will destroy the carbohydrates and proteins, including the materials that make up your skin and muscle. Concentrated sulfuric acid has disfigured many people who have been unlucky enough to come in contact with it. Even when sulfuric acid is diluted the proper way, by adding the acid to a volume of water, it can still result in an extremely hot mixture that might even boil.

Good practice involves using a receiving flask that can contain splashing acid water mixture, such as Erlenmeyer flask, and even chilling the mixture during the dilution. A splash shield can also be placed between the worker and the dilution mixture and it could be done in a fume hood. Heavy neoprene lab gloves, as well as eye protection, are recommended. Students in introductory chemistry classes rarely perform this dilution procedure, because of the high likelihood of accidents.

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