Module 2 - bonding, structure, reactions etc

Question 1

What is made when you neutralise an acid with a metal oxide or hydroxide?

Answer 1

A salt + water

E.g. copper oxide + sulfuric acid
-> copper sulfate + water

Question 2

What is made when you react an acid with an alkali?

Answer 2

A salt + water

E.g. HCl + NaOH -> NaCl + H2O

Question 3

What are acids and bases defined as ?

Answer 3

Acids are proton (H+) donors.

Bases are proton acceptors

Question 4

Define an alkali

Answer 4

A base that dissolves in water releasing hydroxide ions into the solution (OH-)

Question 5

What defines the strength of an acid?

Answer 5

The strength of an acid is determined by how much it dissociates in water

A strong acid will ionise more in water, leaving more H+ ions available to react with other compounds

A weak acid will not ionise as much in water, so there are less protons available to be donated

Question 6

What is made when you react an acid with a metal carbonate?

Answer 6

A salt + water + carbon dioxide

E.g. Magnesium carbonate + hydrochloric acid -> magnesium chloride + water + carbon dioxide

Question 7

What are the special cases for oxidation numbers of certain elements in compounds?

Answer 7

H in metal hydrides is -1 (e.g. NaH, CaH2)

O in peroxide’s is -1 (e.g. H2O2)

O bonded to F is +2

Question 8

While there are many different forms of sulfur and nitrogen, what is the common oxidation number assumed to these 2 elements in a compound ?

Answer 8

Unless you can work it out to be otherwise (eg. You know the oxidation number of everything except sulfur in a compound),

Nitrogen is assumed to be +5
Sulfur is assumed to be +6

So if you have sulfur/nitrogen plus another element with an unknown oxidation number, assume the numbers above for those two.

Question 9

What change in oxidation number constitutes a reduction or oxidation reaction?

Answer 9

Reduction is a decrease in oxidation number

Oxidation is an increase in oxidation number

Question 10

What is made in a reaction between a metal and an acid

Answer 10

A salt + hydrogen

Question 11

What is an orbital

Answer 11

An orbital is the space in which an electron moves

Question 12

What shape is an S-orbital

Answer 12

Spherical

Question 13

What shape is a P-Orbital

Answer 13

Dumbbell shaped

Question 14

When doing the electron configuration, why must electrons must be represented by 2 arrows in different directions?

Answer 14

To represent the two electrons in each orbital spinning in opposite directions

Question 15

When writing electron configurations of ions, how are they different?

Answer 15

You need to remove or add electrons to or from the highest-energy occupied subshell

Question 16

What is ionic bonding?

Answer 16

An ionic bond is an electrostatic attraction between two or more oppositely charged ions

Question 17

What is a ‘giant’ structure

Answer 17

A compound which is made up of the same basic unit repeated over and over

Question 18

What behaviours of ionic compounds are explained by its ionic structure?

Answer 18

• high melting point and boiling point, strong ionic bonds
• conduct electricity when molten or dissolved. The ions in a liquid are mobile and carry a charge, but are fixed when it’s solid
• can dissolve in water. Water molecules are polar so can attract charged ions

Question 19

What is a covalent bond?

Answer 19

A covalent bond is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 20

Name 2 examples of special covalent compounds

Answer 20

• In boron trifluoride, boron has only 6 electrons in its outer shell
• In sulfur hexafluoride, sulfur has 12 electrons in its outer shell

Question 21

What is dative covalent bonding

Answer 21

Where both electrons come from one atom in a covalent bond

E.g. NH4+ is formed by dative covalent bonding. The nitrogen atom donates a pair of electrons to H+

Question 22

How is dative covalent bonding sometimes represented (when drawing the displayed formula of one)

Answer 22

An arrow is drawn from the ‘donor’ atom to the non donor

Question 23

What determines the shape of a molecule

Answer 23

• number of atoms involved in the molecule

- number of lone pairs of electrons

Question 24

What is ‘electron pair repulsion theory’

Answer 24

Electrons are all negatively charged, so electron pairs will repel each other as much as they can

The number of electron pairs in bonds and lone electron pairs determines the structure of a molecule

Question 25

How would you draw a molecule with 2 electron pairs around a central atom?

What is the bond angle?

Answer 25

It’s a straight line, ‘linear’

Bond angle of 180 degrees

Question 26

What shape does 3 electron pairs around a central atom make?
Bond angle?

Answer 26

Central atom with 3 bond pairs equally placed in a triangle shape

Bond angle = 120 degrees

Question 27

What shape does 4 electron pairs around a central atom make (NO LONE PAIRS)?

Bond angle?

Answer 27

Tetrahedral shape. Triangular based pyramid with another bond pair going above the top, central atom. See pg 47 revision guide

Bond angle 109.5 degrees

Question 28

What shape does a central atom with 4 electron pairs around it make (ONE LONE PAIR)?

Bond angle?

Answer 28

Trigonal pyramidal. Triangular based pyramid with 2 electrons on top of the top atom

Bond angle 107 degrees

Question 29

What shape does 4 electrons around a central atom make? (2 LONE PAIRS)

Bond angle?

Answer 29

Makes a v-shape, “bent”, or “nonlinear” with 2 lone pairs on one side and 2 bond pairs on the other side making a V

Bond angle = 104.5

Question 30

What shape does a molecule with 5 electron pairs around a central atom make? Bond angles?

Answer 30

Makes a “trigonal bipyramidal” shape. It’s like 2 triangular based pyramids with their bases attached together.

Some of the bond angles are 90 degrees and some are 120 degrees

Question 31

What shape does a molecule with 6 electron pairs around a central atom make? Bond angle?

Answer 31

Octahedral shape. 2 square based pyramids with their bases joined together

Bond angles of 90 degrees (all)

Question 32

Define electronegativity

Answer 32

An atoms ability to attract the electron pair in a covalent bond

Question 33

What is the general trend for electronegativity?

Answer 33

As you get further right and further up the periodic table, they get more electronegative.

Fluorine is the most electronegative (top right)

Question 34

What are the general properties of substances that have hydrogen bonding?

Answer 34

Soluble in water

Higher boiling and freezing points

Question 35

What elements can form hydrogen bonds when in hydride form?

Answer 35

Nitrogen, fluorine and oxygen

Question 36

Why do simple covalent compounds have low melting and boiling points?

Answer 36

The intermolecular forced between the molecules are weak so don’t need much energy to break

Question 37

What is the oxidation rule for elements on their own?

Answer 37

The oxidation number is always 0 for elements on their own

Question 38

What is the oxidation number of a compound made of the same element?

Answer 38

Compounds with multiple of the same element e.g. H2, O2, P4 etc are always 0

Question 39

What is the rule for the oxidation numbers of the elements in an ionic compound?

Answer 39

The oxidation number of an ionic compound will always add up to the charge on that compound

Question 40

What rule relates oxidation number and the charge of the compound it is found in?

Answer 40

The sum of the oxidation numbers is equal to the charge of the compound

Question 41

What is the oxidation number of an element?

Answer 41

Generally, the oxidation number of an element in a compound is the same as the charge for that element to become a stable ion