When recrystallizing the product 120 mL of boiling water was used. The question

Question

When recrystallizing the product 120 mL of boiling water was used. The question is, why was 120 mL used? What happened if 60 or 200 mL were used inseatd? How would have it figure out if we weren't told how much to use. A picture of the lab is included for hopefully better understanding.
BENZOIC ACID BY THE GRIGNARD METHOD to sink. water in Br Mg OH Ref: see Zubrick, 8th ed., Chapter 9- Clean and Dry, Chapter 12- Melting-Point Experiment, Chapter 13- Recrystallization, Chapter 15- Extraction and Washing, Chapter 17- Sources of Heat, ep and Chapter 22- Reflux and Addition. Place 1.22 g of magnesium metal in a 100 mL flask fitted with an adapter holding a reflux condenser and a dropping funnel. A magnetic stirrer will also be helpful. The entire apparatus must be dry and free of acetone. Add 5 mL of anhydrous ether to the flask. Make a solution of it 7.8 g of bromobenzene in 35 mL off ous ether and add to the dropping funnel. Start the anhydr hs reaction by adding 15 mL of the bromobenzene solution to the flask. Stir the contents until the reaction begins 6-8 minutes then add the bromobenzene solution to the flask at such a rate that the ether boils. Note: If the reaction d begin in this time period, a small crystal of will help initiate the reaction. After the addition reflux with of bromobenzene is complete and the reaction has subsided, heat the mixture under crushed dry warm water for 15 minut Pour the cooled (in ice) Grignard solution onto 25 g of ice in a beaker with stirring. Break up the mass that forms and allow the carbon dioxide gas to escape. Carefully add 50 mL ofice-cold 2M HCl solution with stirring. Transfer the mixture to a separatory funnel, rinsing the beaker with 15 mb ether. separate the layers and extract the aqueous layer with two 15 mL of ether. Combine the ether extracts with the original ether solution in the separatory funnel. Add 50 mL of 2M NaoH solution to the funnel and shake to extract the product. Drain the aqueous layer into a beaker and precipitate the benzoic acid by acidifying the solution with concentrated HC1.

Explanation / Answer

For 1,0 g of impure benzoic acid recrystallisation require 20 ml and later 10-15 ml of water for maximum of recovery of pure benzoic acid. Based on above equation let us assume 100% yield then impure benzoic acid should be 3.34 g, In that case it require 120 mL of water for crystallisation which will give maximum recovery.

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