1.1 Formulae and Equations

Question 1

What is the formula of a compound?

Answer 1

The formula of a compound is a set of symbols and numbers.
Symbols: say what elements are present
Numbers: give ratio of the numbers of atoms of the different elements

Question 2

Formula of water

Answer 2

H2O

Question 3

Formula of carbon dioxide

Answer 3

CO2

Question 4

Formula of sulfur dioxide

Answer 4

SO2

Question 5

Formula of methane

Answer 5

CH4

Question 6

Formula of hydrochloric acid

Answer 6

HCl

Question 7

Formula of sulfuric acid

Answer 7

H2SO4

Question 8

Formula of nitric acid

Answer 8

HNO3

Question 9

Formula of ethanoic acid

Answer 9

CH3COOH

Question 10

Formula of ammonia

Answer 10

NH3

Question 11

Formula of ammonium chloride

Answer 11

NH4Cl

Question 12

Formula of sodium hydroxide

Answer 12

NaOH

Question 13

Formula of sodium chloride

Answer 13

NaCl

Question 14

Formula of sodium carbonate

Answer 14

Na2CO3

Question 15

Formula of sodium hydrogencarbonate

Answer 15

NaHCO3

Question 16

Formula of sodium sulfate

Answer 16

Na2SO4

Question 17

Formula of copper (II) oxide

Answer 17

CuO

Question 18

Formula of copper (II) sulfate

Answer 18

CuSO4

Question 19

Formula of calcium hydroxide

Answer 19

Ca(OH)2

Question 20

Formula of calcium carbonate

Answer 20

CaCO3

Question 21

Formula of calcium chloride

Answer 21

CaCl2

Question 22

Formula of ammonium ion

Answer 22

NH4+

Question 23

Formula of hydrogen ion

Answer 23

H+

Question 24

Formula of lithium ion

Answer 24

Li+

Question 25

Formula of potassium ion

Answer 25

K+

Question 26

Formula of sodium ion

Answer 26

Na+

Question 27

Formula of silver ion

Answer 27

Ag+

Question 28

Formula of barium ion

Answer 28

Ba2+

Question 29

Formula of calcium ion

Answer 29

Ca2+

Question 30

Formula of magnesium ion

Answer 30

Mg2+

Question 31

Formula of copper (II) ion

Answer 31

Cu2+

Question 32

Formula of iron (II) ion

Answer 32

Fe2+

Question 33

Formula of iron (III) ion

Answer 33

Fe3+

Question 34

Formula of aluminium ion

Answer 34

Al3+

Question 35

Formula of bromide ion

Answer 35

Br-

Question 36

Formula of chloride ion

Answer 36

Cl-

Question 37

Formula of fluoride ion

Answer 37

F-

Question 38

Formula of iodide ion

Answer 38

I-

Question 39

Formula of hydrogencarbonate ion

Answer 39

HCO3-

Question 40

Formula of hydroxide ion

Answer 40

OH-

Question 41

Formula of nitrate ion

Answer 41

NO3-

Question 42

Formula of oxide ion

Answer 42

O2-

Question 43

Formula of sulfide ion

Answer 43

S2-

Question 44

Formula of carbonate ion

Answer 44

CO32-

Question 45

Formula of sulfate ion

Answer 45

SO42-

Question 46

Formula of phosphate ion

Answer 46

PO43-

Question 47

How do you write the formula for ionic compounds?

Answer 47

1. Write the symbols of the ions in the compound 2. Balance the ions so that the total of positive and negative ions adds to zero 3. Write the formula without the charges and put the number of ions of each element as a small number following and below the element symbol

Question 48

Define oxidation number.

Answer 48

The oxidation number of an element is the number of electrons that need to be added to (or taken away from) an element to make it neutral

Question 49

List the rules for oxidation numbers.

Answer 49

1. The oxidation number of an uncombined element is zero 2. The sum of the oxidation numbers in a compound is zero. In an ion, the sum equals the overall charge 3. In compounds, the oxidation numbers of a group I metal is +1 and group II metals is +2 4. The oxidation number of oxygen is -2 in compounds (except with fluorine or in peroxides and superoxides) 5. The oxidation number of hydrogen is +1 in compounds except in metal hydrides 6. In chemical species with atoms of more than one element, the most electronegative element is given the negative oxidation number.

Question 50

Why are oxidation numbers used in redox reactions?

Answer 50

To show which species is oxidised and which one is reduced. If oxidation number increases; it is oxidised If oxidation number decreases, it is reduced

Question 51

Name another use of oxidation numbers.

Answer 51

To name compounds unambiguously.

Question 52

How do you write a balanced chemical equation?

Answer 52

1. Write the symbols and formulae of the reactants and products (ensure that they are all correct) 2. Balance the equation by multiplying formulae if necessay (never change a formula) 3. Check to see of the number of atoms are equal on both sides of the eqn. 4. Add state symbols

Question 53

State symbol for solid

Answer 53

(s)

Question 54

State symbol for liquid

Answer 54

(l)

Question 55

State symbol for gas

Answer 55

(g)

Question 56

State symbol for aqueous

Answer 56

(aq)

Question 57

How do you write ionic equations?

Answer 57

1. Write out the chemical equation with state symbols 2. Split any aqueous compounds into its ions 3. Cancel any spectator ions (ions seen in both sides of the eqn) 4. Write out the remaining (uncancelled). This is your ionic equation.