Analytical Chemistry

Question 1

What is the principle of UV-Vis spectroscopy?

Accepted Answer

Measurement of absorption

Answer

UV-Vis spectroscopy is an analytical technique that measures the absorption of ultraviolet and visible light by a sample. When light passes through a substance, specific wavelengths are absorbed by electrons transitioning to higher energy levels. The amount of light absorbed at different wavelengths provides information about the concentration and electronic structure of the absorbing species.

Question 2

Which technique separates compounds based on their boiling points?

Accepted Answer

Gas chromatography

Answer

Gas chromatography (GC) is a powerful analytical technique used to separate and analyze compounds that can be vaporized without decomposition. It separates components of a mixture based on their differential partitioning between a stationary phase and a mobile gas phase, with separation primarily driven by differences in their boiling points and interactions with the stationary phase. Components with lower boiling points typically elute faster.

Question 3

What is the purpose of a reference electrode in potentiometry?

Accepted Answer

To provide a stable potential

Answer

In potentiometry, a reference electrode is crucial because it provides a stable and known potential against which the potential of the indicator electrode is measured. This constant potential allows for accurate determination of the potential difference, which is then related to the concentration of the analyte in the solution. Without a stable reference, precise measurements would not be possible.

Question 4

Which of the following is a primary standard in titration?

Accepted Answer

Sodium carbonate

Answer

A primary standard is a highly pure, stable, non-hygroscopic substance of precisely known composition that can be accurately weighed to prepare a solution of exact concentration. These solutions are then used to standardize other solutions in titration. Sodium carbonate (Na2CO3) meets these criteria and is commonly used as a primary standard for standardizing strong acids.

Question 5

What is the principle of gravimetric analysis?

Accepted Answer

Measurement of mass

Answer

Gravimetric analysis is a quantitative analytical method that determines the amount of an analyte by precisely measuring its mass. The analyte is selectively converted into an insoluble precipitate, which is then isolated, purified, dried, and weighed. The mass of the precipitate is used to calculate the original amount or concentration of the analyte in the sample.

Chemistry Practice Test Practice Test

Chemistry Practice Test Practice Test

Analytical Chemistry