Inorganic Chemistry

Question 1

Name the processes
responsible for the following
phase changes: solid ⇄ gas

Answer 1

Sublimation (s to g)

Deposition (g to s)

Question 2

What is diffusion?

Answer 2

It is the overall movement of particles from an area of high concentration to an
area of low concentration.
E.g. a gas will diffuse through all the space it can find.
E.g. if you spray some perfume in one corner of the room, soon you will be able to
feel the smell at the other end of the room.

Question 3

What is a solubility curve?

Answer 3

It is a curve that shows how the solubility of a substance (in grams per 100 g of
water) changes with temperature.

Question 4

Outline the main assumptions of the kinetic

theory of matter.

Answer 4

a) Matter is made up of atoms, molecules and ions of different sizes.
b) At the same temperature, small particles move faster than large particles
c) As temperature rises, the particles have more kinetic energy and move faster
d) Solids are made up of ordered arrangement of closely packed particles
e) Liquids do not have particles arranged regularly. Particles can move around.
f) In gases, the particles are far apart. They move fast. Their motion is random.

Question 5

Explain what is meant by centrifuging

Answer 5

It is a method for separating out particles of different densities in a substance.
It can be used to separate suspended solids (very small particles of solid) from the
liquid they are suspended in.
It is used when the particles are so small that they can’t be separated via filtration.
In a centrifuge, the sample is spun at high rates. This forces the solid particles to
settle down at the bottom of the tube. The liquid can be decanted.

Question 6

What is an atom?

Answer 6

An atom is the smallest particle of a chemical element that can exist.

Question 7

What is an element?

Answer 7

An element is a substance made up of only one type of atom.

Question 8

How are the element listed and approximately how

many are there?

Answer 8

They are listed in the periodic table; there are approximately 100.

Question 9

Elements can be classified into
two groups based on their
properties; what are these
groups?

Answer 9

Metals and non-metals

Question 10

Elements may combine
through chemical reactions to
form new products; what are
these new substances called?

Answer 10

Compounds

Question 11

What is a compound?

Answer 11

Two or more elements combined chemically in fixed proportions which can
be represented by formulae

Question 12

Do compounds have the same properties as their

constituent elements?

Answer 12

No, they have different properties.

Question 13

What is a mixture? Does it have the
same chemical properties as its
constituent materials?

Answer 13

A mixture consists of two or more elements or compounds not chemically
combined together; the constituent materials keep their own chemical
properties, but the mixture may have different chemical properties (e.g.
melting point) as a whole.

Question 14

What are the methods through which mixtures
can be separated (there are five)? Do these
involve chemical reactions?

Answer 14

Filtration, evaporation/crystallisation, simple distillation, fractional
distillation and chromatography; they do not involve chemical reactions

Question 15

Describe and explain simple

distillation.

Answer 15

Simple distillation is used to separate liquid from a solution – the liquid
boils off and condenses in the condenser. The thermometer will read the
boiling point of the pure liquid. Contrary to evaporation, we get to keep the
liquid (it drips and is collected into a separate beaker).

Question 16

Describe and explain crystallisation/evaporation

Answer 16

Evaporation is a technique for separation of a solid dissolved in a solvent from a
solvent (e.g. salt from H2O).
The solution is heated until all the solvent evaporates; the solids stays in the vessel.
Crystallisation is similar, but we only remove some of the solvent by evaporation to
form a saturated solution (the one where no more solid can be dissolved). Then,
we cool down the solution. As we do it, the solid starts to crystallise, as it becomes
less soluble at lower temperatures. The crystals can be collected and separated
from the solvent via filtration.

Question 17

Describe and explain

fractional distillation

Answer 17

Fractional distillation is a technique for separation of a mixture of liquids.
It works when liquids have different boiling points.
The apparatus is similar to the one of simple distillation apparatus, with the additional
fractionating column placed on top of the heated flask.
The fractionating column contains glass beads. It helps to separate the compounds.
In industry, mixtures are repeatedly condensed and vapourised. The column is hot at the
bottom and cold at the top. The liquids will condense at different heights of the column.

Question 18

Describe and explain filtration

Answer 18

Filtration is used to separate an insoluble solid suspended in a liquid. The
insoluble solid (called a residue) gets caught in the filter paper, because
the particles are too big to fit through the holes in the paper.
The filtrate is the substance (liquid) that comes through the filter paper.
Apparatus: filter paper + funnel.

Question 19

Describe and explain chromatography

Answer 19

Chromatography is used to separate a mixture of substances dissolved in a solvent.
In paper chromatography, we place a piece of paper with a spot containing a mixture
in a beaker with some solvent. The bottom of the paper has to be in contact with
the solvent. The solvent level will slowly start to rise, thus separating the spot
(mixture) into few spots (components).

Question 20

Describe a paper chromatography experiment

Answer 20

a) A start line is drawn near the bottom of the paper. The mixture is spotted on the line.
b) A beaker is filled with small amount of solvent (it cannot touch or go above the start line
when paper is placed in a beaker)
c) Paper is hung on a rod and placed in a beaker.
d) Solvent travels up the paper, thus separating the components.
e) Before solvent level reaches the end, the paper is taken out and the finish line is
marked. The paper is dried.
f) The procedure works when the components dissolve differently in the solvent. More
soluble components travel further up the paper. Less soluble components have a
stronger attraction for the paper and travel less slowly with the solvent, therefore less
further up the paper.
g) Paper is called the stationary phase - it doesn’t move. Solvent is the mobile phase.

Question 21

How is Rfcalculated?

Answer 21

Distance moved by the spot (solute component) / distance moved by solvent.

Question 22

In a paper chromatography experiment, a
compound A was found to have an Rf
value of
0.85 - what does it tell you about the compound?

Answer 22

It has a higher affinity for the solvent than for the paper.

Question 23

What is a separating funnel?

Answer 23

A separatory funnel is an apparatus for separating immiscible liquids.
Two immiscible liquids of different densities will form two distinct layers in
the separatory funnel.
We can run off the bottom layer (the liquid with greater density) to a
separate vessel.

Question 24

Describe the plum-pudding model

Answer 24

The atom is a ball of positive charge with negative electrons embedded in
it.

Question 25

Describe the Bohr/nuclear model and how it | came about

Answer 25

The nuclear model suggests that electrons orbit the nucleus in energy levels (at specific distances from nucleus) – it came about from the alpha scattering experiments conducted by Ernest Rutherford and two students.

Question 26

Later experiments led to the discovery of smaller, positive particles in the nucleus; what are these particles called?

Answer 26

Protons

Question 27

What did the work of James Chadwick provide | evidence for?

Answer 27

The existence of neutrons in the nucleus.

Question 28

Describe the structure of an atom

Answer 28

Describe the structure of an atom

Question 29

State the relative masses and relative charges | of the proton, neutron and electron

Answer 29

Masses: 1, 1, very small (respectively) Charges: 1, 0 , -1 (respectively)

Question 30

Explain why atoms are | electrically neutral.

Answer 30

They have the same number of electrons and protons

Question 31

What is the radius of an atom?

Answer 31

0.1 nm

Question 32

What is the radius of a nucleus and what is it | compared to that of the atom?

Answer 32

1 x 10-14 m and less than 1/10000 of the radius of the atom.

Question 33

What name is given to the number of protons in | the nucleus?

Answer 33

Atomic number

Question 34

Atoms of the same element have the same number of which particle in the nucleus?

Answer 34

Protons

Question 35

Where is the majority of mass of an atom?

Answer 35

The nucleus

Question 36

What is the mass number?

Answer 36

The total number of protons and neutrons in the nucleus.

Question 37

How does one calculate the number of neutrons | using mass number and atomic number?

Answer 37

Subtract the atomic number from the mass number.

Question 38

What is an isotope? Do isotopes of a certain | element have the same chemical properties?

Answer 38

Atoms of the same element (same proton number) that have a different number of neutrons. They have the same chemical properties as they have the same electronic structure.

Question 39

What is the relative atomic mass?

Answer 39

The average mass value of one atom (taking into account the abundance of isotopes), compared to 1/12 of the mass of one carbon-12 atom.

Question 40

Give the electronic configurations of He (2), Be (4), F (9), Na (11), and Ca (20) to demonstrate how shells are occupied by electrons.

Answer 40

``` 2 2,2 2,7 2,8,1 2,8,8,2 ```

Question 41

Describe the properties of noble gases. Discuss | the trends in properties down the group.

Answer 41

Non-metals, colourless gases at room temperature, low boiling points, unreactive (full outer shell; they don’t easily accept or lose electrons). The boiling point increases down the group, as the atoms get heavier.

Question 42

Explain the following: solute, solvent, solution, | miscible, immiscible, soluble, insoluble.

Answer 42

A solute is a substance that is dissolved in a solvent. Together they form a solution. Miscible refers to the substances (particularly liquids) that mix together in all proportions, e.g. water and alcohol. Water and oil are immiscible, i.e. they do not mix. Soluble refers to the substance that can be dissolved in a solvent, e.g. salt in water. An insoluble substance won’t dissolve in a particular solvent.

Question 43

The columns of the periodic table are called?

Answer 43

Groups

Question 44

The rows of the periodic table are called…?

Answer 44

Periods

Question 45

Are elements in the same | group similar or different?

Answer 45

They may have similar chemical properties, as they have the same number of outer shell electrons.

Question 46

In terms of energy levels, what are the differences between elements of the same period?

Answer 46

They have the same number of energy levels

Question 47

Electrons occupy particular energy levels, with each electron in an atom at a particular energy level; which available energy level do electrons occupy?

Answer 47

The lowest available energy level

Question 48

The elements of Group 0 are more commonly | known as…?

Answer 48

The noble gases

Question 49

What makes the periodic table periodic?

Answer 49

Similar properties of elements occur at regular intervals

Question 50

Elements in the same group have the same number of electrons in their outer shell; what does this tell us about their chemical properties?

Answer 50

They have similar chemical properties

Question 51

In terms of shells, what is the difference | between elements in the same period?

Answer 51

They have the same number of shells

Question 52

What change in shell number is seen as one | moves down a group?

Answer 52

The number of shells increases

Question 53

Early periodic tables were incomplete and elements were placed in inappropriate groups if what was to be followed?

Answer 53

The strict order of atomic weights

Question 54

Knowledge of what made it possible to explain why the order based on atomic weights was not always correct?

Answer 54

Isotopes

Question 55

Mendeleev overcame some problems with the table by doing what? He also changed the order of some elements based on what?

Answer 55

Leaving gaps; atomic weights

Question 56

The majority of elements are…?

Answer 56

Metals

Question 57

Elements that react to form positive ions are…?

Answer 57

Metals

Question 58

Elements that do not form positive ions are…?

Answer 58

Non-metals

Question 59

Elements in Group 1 are known as…?

Answer 59

The alkali metals

Question 60

Elements in Group 7 are known as…?

Answer 60

The halogens

Question 61

What is ionic bonding?

Answer 61

Ionic bonding is the transfer of electron(s) from a metal atom to a non-metal atom to form positive and negative ions. There is a relatively strong electrostatic attraction between the positive and negative ions which is called an ionic bond.

Question 62

How are ionic compounds held together?

Answer 62

They are held together in a giant lattice. It’s a regular structure that extends in all directions in a substance. Electrostatic attraction between positive and negative ions holds the structure together.