redox

Question 1

describe what oxidation is in terms of the 3 different wordings?

Answer 1

-gain of oxygen
-loss of electrons
-loss of hydrogen

Question 2

describe what reduction is in terms of the 3 different wordings?

Answer 2

-loss of oxygen
-gain of electrons
-gain of hydrogen

Question 3

what is a redox reaction?

Answer 3

when both reduction and oxidation are going on side-by-side

Question 4

what do oxidising and reducing agents do?

Answer 4

oxidising agents are species that cause another element to be oxidised- it itself is reduced in the reaction

reducing agents are species that cause another element to be reduced- it itself is oxidised in the reaction

Question 5

what are the rules for assigning oxidation states? (4 rules)

Answer 5

1. on simple ions, the oxidation state is equal to the charge on the ion
2. in elements, the oxidation state is always zero
3. the total of all oxidation states must always equal the overall charge of the species
4. in molecules and more complex ions, the more electronegative element is assumed to be the negative ion

Question 6

what is the oxidation state of group 1, 2 and 3 metals?

Answer 6

+1, +2, +3

Question 7

what is the oxidation state of F?

Answer 7

-1

Question 8

what is the oxidation state of Cl, Br and I?

Answer 8

-1 except in compounds with oxygen and flourine

Question 9

what is the oxidation state of Oxygen?

Answer 9

-2 except in peroxides where it is -1 and in compounds with flourine

Question 10

give the list of decreasing priority when it comes to assigning priority for oxidation states?

Answer 10

1
2
3
F
H
O
Cl

Question 11

what does a reduction half equation show?

Answer 11

only shows the parts of a chemical reaction involved in reduction

electrons are on left

Question 12

what does an oxidation half equation show?

Answer 12

only the parts of a chemical equation involved in oxidation

the electrons are on the right

Question 13

what do oxidising and reducing agents act as?

Answer 13

oxidising agents are electron acceptors

reducing agents are electron donors

Question 14

what is the step by step process for writing half equations?

Answer 14

1. work out oxidation numbers for element being oxidised/ reduced
2. add electrons to equal the change in oxidation number
3. check to see that the sum of the charges on the reactant side equals the sum of the charges on the product side

Question 15

what do we do to half equations when the substance that is being oxidised/ reduced contains a varying amount of O?

Answer 15

balance half equations by adding H+, OH- ions and H2O

Question 16

what must be the case in order to combine two half equations?

Answer 16

there must be equal numbers of electrons in the two half equations so that the electrons cancel out

you can multiply the half equations to get equal electrons