Question

In an extraction experiment similar to your expt. 4, you attempt to separate 2-naphthol from cyclohexane, both of which are dissolved in ether. You attempt the separation by extracting the organic layer with a Ì´5% NaOH (aq) solution (made by adding 5.00 g of NaOH to every 100 mL of water). Assuming that all of the base present in the aqueous solution reacts with the phenol during your extractions, what is the minimum volume of the aqueous NaOH solution needed to deprotonate 20.0 g of 2-naphthol in order to extract it into the water layer? Clearly show all calculations. After removal of the phenol from the ether layer, only cyclohexane would remain. Concisely explain how you could efficiently isolate relatively pure cyclohexane from the ether layer.

Answer 1

Answer:

[a]. 108 mL.

[b].

1. use HCL in washing for the neutralization of NaOH.

2. Wash with water.

3. make use of MgSO4 to remove water traces.

4. Evaporate to get the pure cyclohexane

Explanation:

The chemical equation for the reaction between 2-naphthol and Sodium hydroxide is given below as:

C₁₀H₈O + NaOH --------------------------------------------------> C10H7O⁻ Na⁺ + H₂O.

The C10H7O⁻ Na⁺ is  the aqueous phase.

The molarity of Sodium Hydroxide is = [ (mass of sodium hydroxide ) ÷ molar mass sodium  hydroxide × volume] × 1000.

The molarity of sodium hydroxide = [ (5/40) × 100] × 1000 =  1.25 M.

The number of moles of 2-naphthol = mass / molar mass =  20 / 144.17 = 0.138 moles.

Recall that, the formula for the number of moles = concentration × volume. Therefore, the volume of sodium hydroxide is given below as:

Volume of sodium hydroxide = the number of moles of sodium hydroxide ÷  concentration of sodium hydroxide = 0.138 ÷  1.25 = 0.108L = 108 mL.

In order to efficiently isolate relatively pure cyclohexane from the ether layer, the following process must be followed:

1. use HCL in washing for the neutralization of NaOH.

2. Wash with water.

3. make use of MgSO4 to remove water traces.

4. Evaporate to get the pure cyclohexane