Acids and Redox

Question 1

What is the oxidation number for elements?

Answer 1

It is always 0.

Question 2

What is the oxidation number of H2?

Answer 2

It is still 0 because it is made of the same element.

Question 3

What does each atom in a compound have?

Answer 3

It has an oxidation number.

Question 4

What is the oxidation number of an ion?

Answer 4

This is the same as the charge on the ion but the sign comes before the number.

Question 5

What is the oxidation number of oxygen when it is in a compound?

Answer 5

-2

Question 6

What is the oxidation number of hydrogen when it is combined with other elements?

Answer 6

+1

Question 7

What is the oxidation number of F when combined with other elements?

Answer 7

-1

Question 8

What is the oxidation number of H in metal hydrides?

Answer 8

-1

Question 9

What is the oxidation number of O in peroxides?

Answer 9

-1

Question 10

What is the oxidation number of oxygen when bonded to fluorine?

Answer 10

+2

Question 11

What is oxidation?

Answer 11

This is the addition of oxygen.

Question 12

What is reduction?

Answer 12

This is the removal of oxygen.

Question 13

What do redox reactions involve?

Answer 13

These involve reduction and oxidation.

Question 14

Is the gain of electrons reduction or oxidation?

Answer 14

Reduction is the gain of electrons.

Question 15

Is oxidation the loss or gain of electrons?

Answer 15

Oxidation is the loss of electrons.

Question 16

What happens to the oxidation number in reduction?

Answer 16

It decreases.

Question 17

What happens to the oxidation number in oxidation?

Answer 17

This causes an increase in oxidation number.

Question 18

What do acids produce in neutralisation reactions?

Answer 18

They produce salts.

Question 19

What happens when dilute acids undergo redox reactions with some metals?

Answer 19

They produce a salt and hydrogen gas.

Question 20

What do acids always contain in their formulae?

Answer 20

They always contain hydrogen.

Question 21

What does the acid release when dissolved in water?

Answer 21

It releases hydrogen ions as protons.

Question 22

What does a strong acid do?

Answer 22

It completely dissociates.

Question 23

What is complete dissociation?

Answer 23

This is where the acid releases all of its hydrogen atoms into solution.

Question 24

What does a weak acid do in an aqueous solution?

Answer 24

It partially dissociates.

Question 25

What is meant by partial dissociation?

Answer 25

This is where only a small proportion of the available hydrogen atoms are released into the solution.

Question 26

Do organic acids tend to be strong or weak?

Answer 26

They tend to be weak.

Question 27

What are 4 types of bases?

Answer 27

Metal oxides Metal hydroxides Metal carbonates Ammonia

Question 28

What does a base o?

Answer 28

It neutralises an acid to form a salt.

Question 29

Are alkalis bases?

Answer 29

Yes

Question 30

What does an alkaline base do?

Answer 30

They dissolve in water to release hydroxide ions into the solution.

Question 31

What happens in the neutralisation of an acid?

Answer 31

The H+ ions react with a base to form salt and neutral water.

Question 32

What are the H+ ions replaced by in neutralisation reactions?

Answer 32

They are replaced by the metal or ammonium ions from the base.

Question 33

What is formed when an acid is neutralised by a metal oxide or metal hydroxide?

Answer 33

Salt and water only.

Question 34

What is formed in neutralisation reactions with alkalis?

Answer 34

Salt and water.

Question 35

In what type of environment do neutralisation reactions with alkalis take place?

Answer 35

The reactants are in solution.

Question 36

What is produced when an acid is neutralised by a carbonate?

Answer 36

A salt, water and carbon dioxide gas.

Question 37

What is a titration?

Answer 37

This is a technique that is used to accurately measure the volume of a solution that reacts exactly with another solution.

Question 38

What three things can titrations be used for?

Answer 38

Finding the concentration of a solution. Identification of unknown chemicals. Finding the purity of a substance.

Question 39

What is checking purity an important aspect of?

Answer 39

Quality control.

Question 40

What could a small amount of impurity of a drug do to a person?

Answer 40

It could cause a great deal of harm to a patient.

Question 41

What is a standard solution?

Answer 41

This is a solution of a known concentration.

Question 42

What type of flask is used to make up a standard solution?

Answer 42

A volumetric flask is used to make up a standard solution.

Question 43

What should be weighed accurately when preparing a standard solution?

Answer 43

The solid..

Question 44

What should the solid be dissolved in when preparing a standard solution?

Answer 44

Its should be dissolved in distilled water.

Question 45

What amount of distilled water should be used when dissolving the solid for a standard solution?

Answer 45

Less than what will reach the line in the volumetric flask.

Question 46

How should the traces of solution be removed?

Answer 46

With distilled water.

Question 47

How should the volumetric flask be filled?

Answer 47

By adding water drop by drop until the solution has a meniscus that reaches the graduation line..

Question 48

What should be done once the flask has been filled?

Answer 48

The flask should be inverted slowly a few times.

Question 49

Why does the flask need to be inverted?

Answer 49

To mix the solution thoroughly for accurate titration results.

Question 50

What type of flask should be used when preparing a standard solution?

Answer 50

A volumetric flask.

Question 51

What two things are used in acid-base titrations?

Answer 51

A pipette and a burette.

Question 52

In acid-base titrations, what is titrated against what?

Answer 52

A solution of an acid is titrated against a solution of a base.

Question 53

hat is a burette reading recorded to?

Answer 53

The nearest half division, with the bottom of the meniscus on a mark or between two marks.

Question 54

How many decimal places is the burette read to?

Answer 54

2

Question 55

What is the last place of an acid-base titration always either?

Answer 55

0 or 5

Question 56

What is important to use when working out the mean titre?

Answer 56

It is important to use only the closest accurate titres.

Question 57

How do you get the closest accurate titres?

Answer 57

You repeat titres until two agree within 0.10cm.

Question 58

What would happen if all of the titres were included in the mean?

Answer 58

You would lose the accuracy of the titration technique.

Question 59

What will you know from the results of the titration?

Answer 59

Both the concentration of, C1, and the reacting volume, V1, of one of the solutions. Only the reacting volume, V2, of the other solution.