MediumChemistryHigh School (11–12)Organic Compounds with Functional Groups › Alcohols, Phenols and EthersNumerical
A test tube holds 2.35 g of phenol in water…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
A test tube holds of phenol in water. Excess bromine water is added, and a white precipitate of 2,4,6-tribromophenol forms with a yield. Use for phenol, for bromine and for tribromophenol. Find the amount of phenol, the least mass of bromine and the mass of precipitate.
Need a reminder? The key ideaShow
Bromine water: . Kolbe: phenoxide, , then acid gives salicylic acid. Moles are mass divided by molar mass, and a percentage yield multiplies the theoretical amount.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. of phenol, yield.
Step 1. Phenol. .
Step 2. Bromine. Three molecules for each phenol: .
Step 3. Precipitate. Theoretical: . At : .
Check. The product is heavier than the phenol because three bromine atoms, each of , replace three hydrogen atoms.
Answer: , and .
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