CHEM-2141 Laboratory Quizzes Review

These flashcards cover key concepts and procedures from the CHEM-2141 lab quizzes, aiding in revision for exam preparation.

Goggles usage in the laboratory

Goggles must be worn all the time in the laboratory.

Lower melting point causes

Two reasons for a lower melting point: temperature of the environment and contamination with another substance.

Recrystallization temperature conditions

The impurity should be soluble under hot conditions to ensure effective recrystallization.

Eutectic point

The composition at which both substances in a mixture melt at a constant ratio.

Recommended melting point measurement order

1. Quick heating to estimate the melting point; 2. Slow heating to carefully observe melting; 3. Slow heating to confirm careful measurement;

Phases in chromatography

The two phases in normal phase silica gel chromatography are the mobile phase and the stationary phase.

Solvent for non-polar compound extraction

A non-polar solvent should be used to efficiently remove a non-polar compound from a mixture.

Retention factor (Rf)

Rf is calculated as the distance traveled by the compound divided by the distance traveled by the solvent front.

T/F: TLC and column chromatography are the purification techniques, used to isolate the individual compounds from the mixture

TRUE

T/F: TLC results would not develop faster and would not be accurate and consistent, if the atmosphere inside the developing chamber is saturated with solvent vapors

FALSE

Which method below will extract out more amount of solute from aqueous solution?

Use 20 mL of non-polar solvent and extract three times.

List two important guidelines when selecting the appropriate extracting solvent for an acid-base extraction.

• The solvent must be immiscible w/ the other solvents

• The component being extracted must be more soluble in the extracting solvent

Acid-base extraction layers

Carboxylic acid will be in the aqueous layer after adding the base, while the carboxylate will be in the organic layer.

Simple distillation suitability

Simple distillation is effective if the boiling point difference between the substances is greater than 40-50 °C.

T/F: If you are overheating a distillation to a dry flask, then the empty glassware might heat quickly, igniting vapors from the distillation and or the remaining solid residue might contain explosive peroxides.

TRUE

Measurement confirmation before distillation

Secure connections at the joints must be confirmed before turning on the heat.

Vapor phase composition in distillation

At a given temperature, the vapor phase is richer in the more volatile component than the boiling liquid mixture.

Solvent immiscibility rule

The solvent used for extraction must be immiscible with the other solvents present.

What goes first SN1 or SN2, what temperature, and why?

SN2, 100*C, It takes 1 hour to reflux

What is the purpose of the acid in the Sn1 and Sn2 reactions that you will perform on t-butanol and 1-butanol today in the lab?

To protonate the hydroxyl (-OH) group of the alcohol

Role of phosphoric acid in dehydration

Phosphoric acid acts as a catalyst in the dehydration reaction.

For the workup of the reaction in the lab; Exp-9 Dehydration of 2-methylcyclohexanol, what are the organic chemistry basic techniques will not be used

Column chromatography and Crystallization

What are the two sets of temperatures, we must take a good control to gentle boil the reaction mixture and to collect distillate.

80-85; 105-110

Polarimetry experiment guidelines

For accurate preparation, avoid shaking the volumetric flask, which can affect the concentration.

Extracting solvent selection guidelines

The component being extracted must be more soluble in the extracting solvent.

Purpose of Hempel column packing

The packing material provides better vapor-liquid contact, thus increasing purification efficiency.