Chemistry Basics Flashcards

Which separation technique uses differences in solubility and partitioning between a stationary and mobile phase to separate analytes?

Answer: Chromatography

Chromatography separates analytes based on their differential affinities for a stationary phase versus a mobile phase.

When a chemical reaction reaches equilibrium, which of the following is true?

Answer: The forward and reverse reaction rates are equal

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, so the concentrations of reactants and products remain constant.

A spectrophotometer measures absorbance. According to Beer-Lambert Law, absorbance is directly proportional to:

Answer: Concentration of the absorbing substance

Beer-Lambert Law states A = εlc, meaning absorbance is directly proportional to the concentration of the analyte.

Which of the following is true about a saturated solution?

Answer: It contains the maximum amount of dissolved solute at a given temperature

A saturated solution contains the maximum amount of solute that can dissolve in a solvent at a given temperature and pressure.

In the context of laboratory reagents, what does 'hygroscopic' mean?

Answer: The substance absorbs moisture from the air

Hygroscopic substances readily absorb and retain water from the surrounding air, which can affect the accuracy of mass-based reagent preparation.

What is the purpose of a blank in spectrophotometric analysis?

Answer: To zero the instrument using a solution containing everything except the analyte

The blank contains all reagents except the analyte and is used to set the baseline absorbance to zero, correcting for reagent and solvent absorbance.

Which of the following best describes an exothermic chemical reaction?

Answer: It releases heat into the surroundings

Exothermic reactions release energy (heat) into the surroundings, resulting in a negative enthalpy change (ΔH < 0).