2.4 Acids and Redox

Question 1

What do all acids contain ?

Answer 1

Contain H+ ions, which are released when dissolved.

Question 2

What do all alkali’s contain ?

Answer 2

Contain OH- ions, which are released when dissolved.

Question 3

What is a strong acid ?

Answer 3

Fully dissociates all of the H+ ions in a solution. E.g. Hydrochloric acid (HCl)

Question 4

What is a weak acid ?

Answer 4

Partially dissociates, so only releases a few H+ ions in. solution. E.g. Ethnic acid (CH3COOH)

Question 5

What does a metal base produce when reacting with an acid ?

Answer 5

Metal + acid = salt + hydrogen

Question 6

What does a metal oxide/hydroxide produce when reacting with an acid ?

Answer 6

Metal oxide/hydroxide + acid = salt + water

Question 7

What does a metal carbonate produce when reacting with an acid ?

Answer 7

Metal carbonate + acid = salt + water + carbon dioxide

Question 8

What does an alkali produce when reacting with an acid ?

Answer 8

Alkali +acid = salt + water

Question 9

What is a neutralisation reaction ?

Answer 9

When an acid and a base react to form a salt and water. The H+ ions are replaced with metal or ammonium ions.

Question 10

Example of neutralisation reaction

Answer 10

HCl + NaOH = NaCl + H20

Question 11

Ionic equation for neutralisation reaction

Answer 11

H+ + OH- = H20

Question 12

What is oxidation ?

Answer 12

Oxidation is the loss of electrons /gain on oxygen.

Question 13

What is reduction ?

Answer 13

Reduction is gain of electrons / loss of oxygen.

Question 14

Oxidation number rule 1: in terms of atoms

Answer 14

An atom in an element has an oxidation number of 0. (Na = 0)

Question 15

Oxidation number rule 2: in terms of simple ions.

Answer 15

In all simple ions, the oxidation number is always the charge of the ion. (Cl- = -1)

Question 16

Oxidation number rule 3: in terms of compounds

Answer 16

In a compound, the sum of the oxidation numbers is 0. (MgO=0)

Question 17

Oxidation number rule 4: in terms of fluorine

Answer 17

Fluorine in a compound has an oxidation number of -1. (KF= -1)

Question 18

Oxidation number rule 5: in terms of hydrogen

Answer 18

Hydrogen in a compound has an oxidation number of +1 unless it is in a metal hydride, where it is -1.

Question 19

Oxidation number rule 6: in terms of oxygen

Answer 19

Oxygen in a compound has an oxidation number of -2, unless it is bonded to fluorine or in a peroxide. (F20, H2O2)

Question 20

Oxidation number rule 7: in terms of charge of ions in a compound

Answer 20

The sum of the oxidation numbers in a compound ion equals the charge of the ion. (CO3 2- = -2)

Question 21

Oxidation number rule: roman numerals

Answer 21

Roman numerals indicate the oxidation number of the element but no sign is displayed. (Cu (II)SO4)

Question 22

How to work out percentage error ?

Answer 22

Error/ Amount x 100
Need to multiply by 2 is there is two measurements.

Question 23

What is a redox reaction ?

Answer 23

Redox reactions involve reduction and oxidation together. If one happens so does the other.

Question 24

What is a titration reaction used for ?

Answer 24

Used to measure volume of one solution that reacts with exactly with another solution. Used to find the concentration of a solution, identify unknown chemicals and find the purity of a substance.

Question 25

What is a standard solution ?

Answer 25

Standard solution is a solution of a known concentration. A volumetric flask is used to make a standard solution accurately.

Question 26

How to calculate mean titre ?

Answer 26

Only use concordant results (0.1 difference). This keeps the mean accurate to the titration.

Question 27

How to calculate titration ?

Answer 27

1) Find amount, in mol, of solute. (c x v =n)
2) Use equation to find mol of other solute of solution using empirical formula.
3) Work out unknown information about solutes in other solution.

Question 28

What are some disadvantages of the upward delivery tube ?

Answer 28

-Cant measure volume of gas.
-Gas can escape as air is displaced out of bottom of delivery tube.
-Gas must be less dense than air so floats to top of delivery tube.

Question 29

What are some disadvantages of the downward delivery tube ?

Answer 29

-Cant measure volume of gas.
-Gas can escape as it is an upward displacement of air.
-Gas must be denser than air so it stays in the tube.

Question 30

How does the displacement of water gas collecting method work ?

Answer 30

Gas fills the tube and pushes (displaces) water out of the tube. You can measure the volume of gas through displacement of water.

Question 31

What is a disadvantage of the displacement of water method ?

Answer 31

Can only work for collecting gases that are insoluble in water.

Question 32

How does the gas syringe collecting method work ?

Answer 32

Allows you to measure volume of gas as it pushes syringe outward due to pressure build up in apparatus. The syringe move to keep pressure the same throughout.

Question 33

What is an advantage for the gas syringe method ?

Answer 33

All gases can be collected using the syringe method.

Question 34

What is a disproportionation reaction ?

Answer 34

When an element is both oxidised and reduced in the same reaction.

Question 35

What happens to the oxidation number if an element has been oxidised ?

Answer 35

The oxidation number goes up if an element has been oxidised as it has lost electrons.

Question 36

What happens to oxidation number if an element has been reduced ?

Answer 36

The oxidation number goes down if the element has been reduced as it has gained electrons.