Module 2 Reactions And Calcualtions

Question 1

What is the oxidation number

Answer 1

Value given to an element in a chemical species which represents number of electrons lost/gained

Question 2

How is the oxidation number written

Answer 2

-2 not 2-, that’s charge

Question 3

What do the Roman numerals show

Answer 3

Oxidation state of transition metals and other elements

Question 4

What are the first 8 Roman numerals

Answer 4

1=l 2=ll 3=lll 4=lv 5=v 6=vl 7=vll 8=vlll

Question 5

What is the oxidation number of c in CO

Answer 5

O is -2 due to rule 6 so to cancel out +2

Question 6

What is the oxidation number of S in S2O3^2-

Answer 6

(-2)3=-6-2=-4 so opposite which is +4 then half as it goes from s2 and you want s, so +2

Question 7

What is the name of SnO2

Answer 7

(-2)2=-4 so Tin (lv) oxide

Question 8

What is the name of FeCl3

Answer 8

(-1)3=-3 so iron (lll) chloride

Question 9

What are the 7 rules for assigning oxidation numbers

Answer 9

1. Oxidation number of a neutral element is O eg Na=O 2. Oxidation of a monoatomic ion is same as charge eg Na+=+1 3. In compounds, group 1 is +1, group 2 is +2, group 3 is +3. 4. Hydrogen in a compound, usually +2 except hydrides eg NaH. 5. Fluorine always -1 in compounds. 6. Oxygen in compounds usually -2 except peroxides eg H2O2. 7. Cl, Br,I usually -1 except ocl2 and NaclO3. 8. Sum of all oxidation numbers in a neutral compound=0. 9. Sum of all oxidation numbers in a poly atomic ion=charge

Question 10

What is water of recrystallisation

Answer 10

Some solid ionic compounds have trapped water in then when they are formed from their aqueous solutions.

Question 11

What is a hydrated salt

Answer 11

A solid salt containing water of crystallisation

Question 12

What is a anhydrous salt

Answer 12

Doesn’t contain water of crystallisation

Question 13

What is the oxidation state of P in P4

Answer 13

0

Question 14

Give range of oxidation state of phosphorus

Answer 14

+5 to -3

Question 15

Define half equation

Answer 15

Shows 1 element/ion and movement of electrons

Question 16

What does OILRIG stand for

Answer 16

Oxidation is loss of electrons/gain of oxygen and reduction is gain of electrons/loss of oxygen

Question 17

Define oxidising agent

Answer 17

Species that causes another species to be oxidised (reduced itself)

Question 18

Define reducing agent

Answer 18

Species that causes another species to be reduced (oxidised itself)

Question 19

What does an increase in oxidation number mean

Answer 19

Oxidised

Question 20

What does a decrease in oxidation number mean

Answer 20

Reduced

Question 21

Define a disproportionation reaction

Answer 21

One element has been both oxidised and reduced in a reaction

Question 22

What steps do you follow to make a half equation

Answer 22

Balance number of atoms on each side, work out charge on each side, add e- to more positive side to balance charge

Question 23

What is a redox equation

Answer 23

When oxidation and reduction happen at the same time in a reaction