Chemistry Laboratory Techniques 2

What is the term for process in which two immiscible liquids are mixed to transfer any chemical compound of interest from one phase to another?

• Filteration

• Distillation

• Liquid-Liquid Extraction

• Decanting

Which of the following statements is FALSE about procedures for Liquid-liquid extraction

• Venting of the funnel is necessary to release built up pressure during shaking

• The effectiveness of extraction depends on the number of extractions

• NaCl is added into the sample if an emulsion is formed to separate the layers  

• Drying agents are added along with the sample inside the separatory funnel for maximum extraction

Meshya dissolved 0.5g of Compound B in 20 mL of water and poured the solution in a separating funnel. She then added 10 mL of organic solvent, invert and left the mixture to stand for a few minutes. After the extraction, she found out that the distribution coefficient (K_pc) of Compound B between organic solvent / water is 8.33.

 

Which of the following represents the mass of Compound B that has transferred into the organic solvent?

• 0.2043 g

• 0.4023 g

• 0.2034 g

• 0.4032 g

Which of the following is the correct formula to calculate the distribution coefficient (K_pc)?

• K_pc =

  Concentration of solute in organic solvent /

  Concentration of solute in water

• K_pc =

  Concentration of solute in water /

  Concentration of solute in organic solvent

• K_pc =

  Concentration of solute in organic solution /

  Concentration of solute in water

• K_pc =

  Concentration of solute in water /

  Concentration of solute in organic solution

Which of the following completes the statement below?

“Inorganic substances dissolves in the ____________layer whereas organic compounds dissolves in the ____________layer.”

• inorganic; inorganic

• organic; organic

• inorganic; organic

• organic; inorganic

Which of the following statements is FALSE about Soxhlet extraction

• The Soxhlet set-up is designed to perform continuous extraction automatically 

• Both condensation and evaporation help recirculate the solvent in the Soxhlet set-up

• The sample and boiling chips are placed in the round bottom flask fitted with the Soxhlet extractor and condenser

• None of the above

What is the purpose of the siphon tube in the Soxhlet extractor?

• To ensure the continuous circulation of the solvent through the sample  

• To contain the sample throughout the extraction

• To collect the extracted sample

• All the above

Steam distillation is a method of separating liquids immiscible in water and low volatility, at temperatures below their ______________

• Melting point

• Boiling point

• Triple point 

• Critical point

To avoid the impurities from splashing over the distillate during steam distillation, distillation flask is sometimes attached with a ____________to avoid mixture contaminating the condenser.

• Claisen adapter

• Still head adapter

• Vacuum adapter

• Dropping funnel

How is hot water introduced into the steam distillation set-up without the presence of the steam generator?

• Claisen funnel

• Dropping funnel

• Vacuum adapter 

• Still head adapter