Physical CAT

Question 1

What are the properties of ionic compounds?

Answer 1

Water soluble
High melting point
Conduct electricity when molten or aqueous

Question 2

Ionic bonds

Answer 2

Electrostatic attractions between ions of opposite charges

Question 3

Bond strength (low to high)

Answer 3

Hydrogen, ionic, covalent

Question 4

Dative bonds

Answer 4

Covalent bonds in which both electrons in the bond come from one atoms

Question 5

Which two bonds form lattices?

Answer 5

Ionic, metallic

Question 6

What are the two forms of covalent?

Answer 6

Simple molecular
Giant covalent

Question 7

Properties of diamond

Answer 7

Thermal conductor
Not electrical conductor
High melting point

Question 8

How many carbons are carbons in graphite bonded to?

Answer 8

3

Question 9

Graphite properties

Answer 9

High melting point
Insoluble in solvents
Soft electrical conductor

Question 10

Linear bond

Answer 10

If the central atom of a molecule has two electron pairs, it will likely adopt a linear geometry.
The bond angle will be 180

Question 11

What is trigonal planar?

Answer 11

If the central atom of a molecule has three electron pairs, it will likely adopt a trigonal planar geometry.
The bond angle will be 120

Question 12

Tetrahedral

Answer 12

If the central atom of a molecule has four electron pairs, it will likely adopt a tetrahedral geometry.
The bond angle will be 109.5

Question 13

Trigonal bipyrimidal

Answer 13

If the central atom of a molecule has five electron pairs, it will likely adopt a trigonal bipyramidal geometry.
Molecules with this shape have two bond angles:
A 120o angle around the equator.
A 90o angle from equator to apex.

Question 14

How much do lone pairs reduce the bond angle?

Answer 14

2.5 degrees

Question 15

When is a molecule polar?

Answer 15

A molecule is polar if there is a charge separation between each side of the molecule.

Question 16

What is the scale used to measure polarity?

Answer 16

Pauling scale

Question 17

What is the most electronegative element?

Answer 17

The most electronegative element is fluorine, with a value of 4.0

Question 18

Bent/angular

Answer 18

Bond angles 104.50
2 electron pairs and 2 bonding pairs

Question 19

What range of electronegativity is a polar covalent bond?

Answer 19

0.4-1.7

Question 20

Above what value of electronegativity are ionic bonds?

Answer 20

1.7

Question 21

Intermolecular forces weak to strong

Answer 21

Van der Waals, dipole-dipole, hydrogen

Question 22

What affects the strength of induced dipole-dipole bonds?

Answer 22

Molecules with more electrons.
This is because they will have larger fluctuations in electron density.
This leads to larger temporary dipoles and stronger dipole-dipole interactions.

Question 23

Which elements can hydrogen form hydrogen bonds with?

Answer 23

N, O, F

Question 24

Trigonal pyramidal

Answer 24

3 bonding pairs
1 lone pair

Question 25

What increases the melting point of a metal?

Answer 25

More electrons donated to delocalised sea as the ions have a stronger attraction to electrons

Question 26

Is thermal decomposition endothermic or endothermic?

Answer 26

Endothermic

Question 27

What is enthalpy?

Answer 27

An enthalpy change is a measure of the heat given out or taken in during a process. When objects are heated, they use energy to expand. Enthalpy takes into account the energy used in the expansion

Question 28

What is the enthalpy change?

Answer 28

The enthalpy change of a reaction is a sum of the individual bond enthalpies being broken and made during the reaction.

Question 29

Standard conditions

Answer 29

A pressure of 1 bar or 100 kPa. A temperature of 298K. A substance's most stable state at 298K and 1 bar pressure

Question 30

What is the symbol for standard enthalpy of combustion?

Answer 30

ΔcHθ

Question 31

What is the symbol for the enthalpy change of formation?

Answer 31

ΔfHθ

Question 32

The standard enthalpy change of combustion is defined as:

Answer 32

The enthalpy change when one mole of a substance in its standard state burns completely in oxygen under standard conditions of 298K and 100kPa pressure

Question 33

The standard enthalpy change of formation is defined as

Answer 33

The enthalpy change when one mole of a substance is formed in its standard state from the pure elements in their standard states under standard conditions of 298K and 1 bar pressure

Question 34

Calorimetry can be inaccurate due to:

Answer 34

Heat lost to the surroundings. Any incomplete combustion that may take place. Loss of some reactant that evaporates before it combusts.

Question 35

The equation to calculate enthalpy changes from temperature changes is

Answer 35

q = m × c × ΔT q is the heat energy. m is the mass of the sample. c is the specific heat capacity. ΔT is the temperature change. If the pressure is constant, q = ΔcH

Question 36

Enthalpy change=

Answer 36

q/moles

Question 37

What is bomb calorimetry?

Answer 37

Bomb calorimetry uses a machine called a bomb calorimeter to measure enthalpy changes of combustion. This process involves burning a sample of a compound in a sealed vessel and measuring the temperature change

Question 38

Hess’ Law

Answer 38

The enthalpy change of a reaction is independent of the pathway

Question 39

Bond enthalpy

Answer 39

the enthalpy change when one mole of bonds is broken in the gas phase

Question 40

Why may bond enthalpies be inaccurate?

Answer 40

Mean bond enthalpies are only valid in the gas phase. You might not be doing your reaction in the gas phase. Bond enthalpies depend on the particular molecule, whereas mean bond enthalpies are quoted generally.