Oxidising and reducing

Question 1

What do displacement reactions normally involve?

Answer 1

a metal high in the ECS reacting with the ions of a metal lower in the ECS

Question 2

What is OILRIG?

Answer 2

Oxidation
Is 
Loss
Reduction
Is 
Gain

Question 3

What are the only metals that react with acids?

Answer 3

metals above hydrogen in the ECS

Question 4

What is a reducing agent?

Answer 4

a substance which donates electrons. In donating electrons, a reducing agent causes the reduction of another element, and in the process, is oxidised.

Question 5

What is an oxidising agent?

Answer 5

a substance which accepts electrons. An oxidising agent causes the oxidation of another reactant, and in the process is reduced

Question 6

Where are the best reducing agents found and why?

Answer 6

substances which easily give away/ donates electrons, e.g. group 1. They have low electronegativity. These substances are found at the top of the ECS, e.g. lithium and caesium

Question 7

Where are the best oxidising agents found and why?

Answer 7

who easily accept electrons e.g. group 7. They have high electronegativity values. These substances are found at the bottom of the ecs e.g. fluorine and chlorine.

Question 8

Apart from elements what does the ECS also contain?

Answer 8

compounds, group ions and molecules which can all act as oxidising or reducing agents

Question 9

Give an example of a strong oxidising agent that is a compound?

Answer 9

permanganate ion which is reduced and converted to manganese ions

Question 10

Give an example of a molecule which is an oxidising agent?

Answer 10

Hydrogen peroxide

Question 11

Give an example of a molecule which is a reducing agent?

Answer 11

carbon monoxide

Question 12

What are the 5. rules for writing out complex ion-electron equations?

Answer 12

1. Write out equations with ions named in question and balance non-oxygen element
2. Balance oxygen by adding water to opposite side
3. Balance hydrogen by adding hydrogen ions to opposite side
4. Calculate charge on each side
5. Balance charges by adding electrons to side containing hydrogen ions.

Question 13

What are oxidising agents used as? (3)

Answer 13

biocides, disinfectants and bleaches

Question 14

What are biocides used for?

Answer 14

killing fungi and bacteria, and inactivating viruses

Question 15

Give a common strong oxidising agent used in disinfectants?

Answer 15

sodium chlorate

Question 16

What can bleaches be used with? give an example of a common oxidising agent?

Answer 16

textiles, paper and hair. hydrogen peroxide is commonly used is hair bleach. The oxidation process can change the structure of coloured compounds and cause them to become colourless

Question 17

What are redox titrations based on?

Answer 17

redox reactions

Question 18

What is a standard solution?

Answer 18

solution of an accurately known

Question 19

How would you prepare a standard solution(use vitamin C)|?

Answer 19

a vitamin C tablet was dissolved in 50cm3 of water in a small beaker.
The solution was then transferred to a 250cm3 standard flask
The beaker was washed out with water and the rinsings were then transferred to the standard flask
Very carefully, water was finally added to the graduation mark (250cm3 line) on the standard flask with a dropping pipette. The flask was then stoppered and inverted several times.

Question 20

How would you carry out a titration(use vitamin C)|?

Answer 20

25cm3 of the vitamin C solution was taken and pipetted into a conical flask.
A few drops of starch indicator was added to the conical flask.
The iodine solution was prepared with a concentration of 0.025 mol l-1 and added from the burette to the conical flask.
when the solution turned blue/black the volume of the burette was noted
The experiment was repeated until concordant results were obtained

Question 21

What is chromatography?

Answer 21

a method of separation of mixtures

Question 22

What are the 2 different types chromatography ?

Answer 22

paper chromatography

Gas-liquid chromatography

Question 23

What does paper chromatography measure?

Answer 23

the distance moved by the separated substance in relation to the distance moved by the solvent

Question 24

What does separation usually depend on?

Answer 24

the size of the molecules (larger molecules take longer to separate)
the polarity of molecules

Question 25

What is gas chromatography?

Answer 25

uses an unreactive gas, e.g. helium. A liquid sample mixture is injected into the column and vaporised before the gas (helium) takes it through the column.

Question 26

Why is gas chromatography useful?

Answer 26

it can separate out complicated mixtures of chemicals using only a small sample of material

Question 27

What is the name given to the chart recorder in which a computer presents the results from gas chromatography?

Answer 27

chromatogram

Question 28

What is the retention time?

Answer 28

the time it takes for a peak to appear

Question 29

Describe the retention time for small and large molecules?

Answer 29

small molecules vaporise quickly and appear first.

Larger molecules take longer to pass through the chromatography instrument

Question 30

What does the area under the graph indicate?

Answer 30

how much of a substance is present

Question 31

What are the 4 uses of chromatography?

Answer 31

testing blood alcohol levels
food industry (to analyse components of a substance or detect contaminants)
medicine (to determine the components of a potential drug)
environmental (to monitor the components of water supply)