Chapter 06 - Chemical Formulae and Equations

Question 1

What do chemical formulae tell us?

Answer 1

The ratio of elements combined in one unit of substance, they contain chemical symbols (indicates the element) and subscript (indicates the number of atoms present in each element)

Question 2

What are the 3 types that elements can exist as?

Answer 2

1) Monoatomic elements
2) Diatomic elements
3) Polyatomic elements

Question 3

What are monoatomic elements?

Answer 3

Monoatomic elements have uncombined atoms with fully filled valence electron shells that exist independently (e.g. noble gases)

Question 4

What are diatomic molecules?

Answer 4

Molecules that have 2 chemically combined atoms (e.g. H2, I2)

Question 5

What are polyatomic molecules?

Answer 5

Molecules that have 3 or more chemically combined atoms (e.g. Sulfur, Phosphorus)

Question 6

What are the 5 main polyatomic ions?

Answer 6

1) Ammonium ions
2) Hydroxide ions
3) Nitrate ions
4) Carbonate ions
5) Sulfate ions

Question 7

What is the chemical symbol for ammonium ions?

Answer 7

NH4+

Question 8

What is the chemical symbol for hydroxide ions?

Answer 8

OH-

Question 9

What is the chemical symbol for nitrate ions?

Answer 9

NO3-

Question 10

What is the chemical symbol for carbonate ions?

Answer 10

CO3 ^2-

Question 11

What is the chemical symbol for sulfate ions?

Answer 11

SO4 ^2-

Question 12

What are the good to know ions?

Answer 12

1) Hydrogen carbonate ions
2) Ethanoate ions
3) Manganate (III) ions
4) Dichromate (VI) ions
5) Phosphate ions

Question 13

What is the chemical symbol for hydrogen carbonate ions?

Answer 13

HCO3-

Question 14

What is the chemical symbol for ethanoate ions?

Answer 14

CH3COO-

Question 15

What is the chemical symbol for manganate (III) ions?

Answer 15

MnO4-

Question 16

What is the chemical symbol for dichromate (VI) ions?

Answer 16

Cr2O7 ^2-

Question 17

What is the chemical symbol for phosphate ions?

Answer 17

PO4 ^3-

Question 18

How do you identify the valency of an element?

Answer 18

By looking at its group number in the periodic table (e.g.
Group 1 = Valency 1
Group 13 = Valency 3
Group 15 = Valency 3)

Question 19

As transition metallic elements have variable valencies, their valencies are indicated by a ____ ____

Answer 19

Roman numeral (e.g.
Copper (II) = Valency 2
Lead (IV) = Valency 4
Manganese (VI) = Valency 6)

Question 20

Chemical formulae that are fixed are ____ while chemical formulae that are not fixed are ____

Answer 20

compounds, mixtures

Question 21

What are the 4 steps in writing chemical formulae?

Answer 21

1) Write the respective valency and criss-cross
2) If valencies are equal, just write out formula
3) If there are more than 1 polyatomic ion, use brackets
4) Reduce the ratio by a common factor if possible

Question 22

What are the valencies for zinc and silver?

Answer 22

Zinc = 2 (Zn2+)
Silver = 1 (Ag+)

Question 23

What are the 2 key points when naming an ionic compounds containing 2 elements

Answer 23

1) The metallic elements comes before the non metallic element
2) Non-metallic elements end with ‘ide’ (e.g. calcium + chlorine = calcium chloride)

Question 24

Only one type ion will not change its name after combining with other elements. What ion is that?

Answer 24

Polyatomic ions (e.g. sodium carbonate, potassium sulfate)

Question 25

What are the 3 key points when naming a covalent compound?

Answer 25

1) The first element name remain unchanged
2) The second element name ends with ‘ide’
3) A prefix is used for the second element depending on the number of atoms involved
(1 atom = mono
2 atoms = di
3 atom = tri
4 atoms = tetra)
Certain covalent compounds have special names (e.g. ammonia, water)

Question 26

Atoms can neither be ____ nor ____

Answer 26

destroyed nor created
The sum of atoms before a reaction = the sum of atoms after a reaction

Question 27

What are the 4 state symbols?

Answer 27

1) Solid (s)
2) Liquid (l)
3) Gas (g)
4) Aqueous (aq) - dissolved in water

Question 28

Name 2 common solids

Answer 28

1) Most metals (Fe, Cu)
2) Ionic compounds (NaCl)
3) Sulfur (S)
4) Phosphorus (P)
5) Carbon (as graphite/diamond)

Question 29

Name 2 common liquids

Answer 29

1) Water
2) Mercury
3) Bromine

Question 30

Name 2 common gases

Answer 30

1) Oxygen
2) Nitrogen
3) Hydrogen
4) Chlorine
5) Fluorine
6) Noble gases

Question 31

Name 2 common aqueous substances

Answer 31

1) Acids
2) Bases
3) Salts (when dissolved in water)

Question 32

What are the 5 steps to writing chemical equations

Answer 32

1) Write the chemical formulae of products and reactants
2) List the number of atoms presents in each element
3) Add molecules to balance
4) Re count the number of atoms on each side and make sure they are the same
5) Write down the final equation

Question 33

What are the 3 steps to converting word equations to chemical equations

Answer 33

1) Identify reactants and products and place them in a word equation
2) Convert the chemical names into chemical formulae
3) Balance the chemical equation

Question 34

What are the 2 types of balanced ionic equations?

Answer 34

1) Solubility of substances in water
2) Change in oxidation states

Question 35

What are the 3 steps to writing an ionic equation?

Answer 35

1) Identify the ionic compounds that are soluble (forming aq solutions) and will dissociate into ions in water (Insoluble substance can’t dissociate)
2) Cancel out spectator ions (ions that remain the same in their original states before and after a chemical reaction)
3) Write a balanced ionic equation with state symbols