Redox

Question 1

Oxidising agent

Answer 1

-chemical that acts on another substance to oxidise it(it’s getting reduced)(electron acceptor)
-remove electrons
-found on the bottom left hand side of the electrochemical series)

Question 2

Reducing agent

Answer 2

chemical that acts on another substance to reduce it(its getting oxidised)(electron donor)
-donate electrons
-top right of ECS

Question 3

Strongest Reducing Agents

Answer 3

The elements with low electronegativities (metals) tend to form ions by losing electrons
(oxidation) and so can act as reducing agents. The strongest reducing agents are found
in group 1.

Question 4

Strongest Oxidising Agents

Answer 4

The elements with high electronegativities (non-metals) tend to form ions by gaining
electrons (reduction) and so can act as oxidising agents. The strongest oxidising agents are
found in group 7.

Question 5

why is it necessary to periodically remove stopper

Answer 5

replenish oxygen

Question 6

Use of oxidising agents

Answer 6

-are used because of their effectiveness which they can kill fungi, and bacteria and can inactivate viruses
-can be used as bleach for clothes and hair because its effective in breaking down compounds

Question 7

Example of oxidising agents

Answer 7

-dichromate and permanganate ions are strong oxidising agents in acidic solutions(useful in redox titrations and organic reactions)
-hydrogen peroxide

Question 8

Example of reducing agents

Answer 8

carbon monoxide is a gas that can be used as a reducing agent as it oxidises to carbon oxide.

Question 9

Titration(volumetric analysis)

Answer 9

a method used to determine the concentration of a solution by reaction with another solution of known concentration.

Question 10

Standard Solution

Answer 10

A standard solution is a solution of accurately known concentration

-Weigh out the chemical and add to a beaker.
-Add a small volume of water to dissolve the chemical.
-Pour solution into standard (volumetric) flask.
- Rinse beaker with de-ionised water and pour washings into the standard flask.
-Top up the solution to the mark using de-ionised water.
-Invert the standard flask to mix the solution.

Question 10

Concordant results

Answer 10

averages can only be calculated from concordant results – within 0.2cm3

Question 11

Pipette

Answer 11

A pipette is used to transfer a known volume of A liquid into a flask

Question 11

Burette

Answer 11

A burette is used to add small controlled volumes to flask

Question 12

Reproducability/reliability

Answer 12

Information given by any variations in the values obtained when a measurement is repeated.

Question 13

Accurate

Answer 13

How close the measurements are to a known value.

Question 14

Precise

Answer 14

When the measurements are close to each other. They may not be accurate.

Question 15

Deionised water

Answer 15

Deionised (distilled) water is used because tap water contains dissolved ions that may react with the chemicals and change their concentrations.

Question 16

Titration example

Answer 16

PREPARE VITAMIN C SOLUTION
-Dissolve a vitamin C tablet in about 50cm3 of de-ionised water.
-Add the vitamin C to a standard flask.
-Rinse beaker with de-ionised water and add washings to 250cm3 standard
flask.
-Carefully top up to the graduation mark with de-ionised water.
-Invert the flask to mix solution.
-Pipette should be rinsed out with vitamin C.
-Burette should be rinsed out with iodine solution.
-Flask rinsed out with deionised water
-White tile to show the end point more clearly