Unit 2 AOS3

Question 1

What is meant by absorbance?

Answer 1

Molecules can absorb energy of specific wavelengths. If this occurs in the visible spectrum then the substance will appear coloured. Absorption spectra are the reverse of emission spectra, with dark lines on a rainbow spectrum.

Question 2

What is meant by transmittance?

Answer 2

The opposite of absorbance; A measure of the proportion of light that has been transmitted through a substance (or solution), where 100% transmittance means that no energy has been absorbed.

Question 3

Purpose of a volumetric flask

Answer 3

Makes up an accurately known volume of solution

Question 4

Purpose of a volumetric pipette

Answer 4

Dispenses an accurately known volume (aliquot) of a solution

Question 5

Purpose of a volumetric pipette

Answer 5

Dispenses an accurately known volume (aliquot) of a solution

Question 6

How many decimal places on a volume measurement made with a burette?

Answer 6

Two decimal places, but the second decimal place is always 0 or 5 (ie nearest 0.05mL)

Question 6

What is a primary standard substance?

Answer 6

A substance that can be prepared pure and dissolved in water to make a solution whose concentration is accurately known

Question 6

Purpose of a burette

Answer 6

Delivers an accurately known but variable amount of solution

Question 6

What is an aliquot?

Answer 6

An accurately known volume of a solution

Question 7

What are the features of a primary standard?

Answer 7

Can be made pure. Does not degrade or react with air. Known molar mass. Preferably dissolves well in water and is inexpensive.

Question 8

What is a primary standard solution?

Answer 8

A solution containing one solute, that has been prepared by dissolving a known mass of that solute in a known volume of pure water. As a result the concentration is accurately known.

Question 9

What is the name given to the solution in the burette during volumetric analysis?

Answer 9

Titrant

Question 10

What is the name given to the solution in the conical flask during volumetric analysis?

Answer 10

Analyte

Question 11

What name is given to the volume of titrant dispensed into the conical flask during a titration?

Answer 11

Titre

Question 12

What is the total range of concordant titres?

Answer 12

0.10 mL

Question 13

What is a mean titre; how is it calculated?

Answer 13

The average of all concordant titres in a titration experiment. Calculated to two decimal places.

Question 14

What is a dilution factor and how is it calculated?