Topic 1

Question 1

Formula for pressure? Give units for each of the 5 values

Answer 1

PV = nRT

Pressure - pascals
n = moles
R = 8.31 Joules per kelvin mole (J k^-1 mol^-1)
V = m^3
T = kelvin

Question 2

Describe relationship between pressure, temperature and volume

Answer 2

Volume is INVERSELY proportional to pressure
temperature is directly proportional to volume
temp is DP to pressure
V is directly proportional to 1/P and vice versa

Question 3

Trick for limiting reactant?

Answer 3

If asked to find limiting reactant, calculate actual number of moles of each reactant, then divide by coefficient to find the limiting reactant based on which one is smaller. but REMEMBER: when asked to find the yield of one of the products you use the ACTUAL number of moles and do the ratio thing with that, not with the divided coefficient values.

Question 4

How do you convert from cm3 to m3 for the pressure equation?

Answer 4

cm3 -> m3: divide number by 10^6

Question 5

What is the standard temperature and pressure? (STP)

Answer 5

Temp - 273 kelvin

Pressure - 1 x 10^5 pascals

Question 6

Equation for molar volume of a gas?

Answer 6

Molar volume = moles x 22.7

Question 7

What does the 22.7dm3 represent?

Answer 7

At STP, 1 mole of any gas occupies 22.7 dm^3 volume

Question 8

How to determine molar mass of a gas experimentally?

Answer 8

To collect the gas, a measuring cylinder is inverted and filled with water

measuring cylinder filled with known volume of gas from a cigarette lighter

mass of lighter recorded before and after

find change in mass in lighter

Find volume collected - convert to m3

convert temp to kelvin

R = 8.31 J k-1 mol-1

P = atmospheric pressure of water - vapour pressure

substitute these into M = mRT/PV

find molar mass VOILAAAA

Question 9

How to calculate percentage area of the molar mass method?

Answer 9

Experimental - theoretical/theoretical x 100

Question 10

Why is the experimental value less than the theoretical value for molar mass?

Answer 10

Lighter not dried completely before weighing
Liquid may be a mixture of propane and butane
Pressure of gas not equalised with pressure of room

Question 11

Assumptions of the ideal gas law? (PV=nRT)

Answer 11

Particles are in constant, straight line, random motion

Collisions between particles are elastic with no loss in kinetic energy

No intermolecular forces acting between particles

Question 12

Under what two conditions do ideal gases deviate the most?

Answer 12

High pressure
low temperature
Under these conditions, product of PV/RT is no longer equal to 1

Question 13

Describe the ideal gas deviation curve

Answer 13

A low temperature and a high pressure cause the most deviation

Question 14

Ideal gases have virtually no what?

Answer 14

volume
intermolecular forces

however, at high pressures, space between particles is reduced and volume of real gases cannot be negligible

real gases deviate most from ideal gas behaviour under HIGH PRESSURE and LOW TEMP

• intermolecular forces have an effect on the pressure of a real gas compared to an ideal gas
• IMF reduces collisions with walls of container
• pressure exerted decreases so observed pressure is less for a real gas than ideal gas

Question 15

Definition of an element

Answer 15

A substance that cannot be broken down by chemical means into simpler substances

Question 16

Definition of a compound

Answer 16

2 or more elements chemically bonded together

Question 17

Definition of a mixture

Answer 17

A mixture contains more than one element and/or compound not chemically bonded together and so retain their individual properties. Their composition is not fixed

Question 18

Homogenous mixtures + example?

Answer 18

Have uniform properties and composition e.g: air, brine, amalgum.

Question 19

Heterogenous mixtures + example?

Answer 19

Have non-uniform composition and properties. e.g: salt and sand, oil and water. Properties not the same throughout. Can be separated

Question 20

Describe the difference in property of components of these mixtures and the technique used to separate them:

i) Sand and salt
ii) Hydrocarbons in crude oil
iii) iron and sulfur
iv) pigments in food colouring
v) Different amino acids

Answer 20

i) Solubility in water, solution and filtration
ii) Boiling point, fractional distillation
iii) magnetism, response to a magnet
iv) absorption to solid phase, chromatog
v) net charge at fixed pH, gel electrophoresis

Question 21

Describe the composition of a solid

Answer 21

Particles closely packed together

Inter-particle forces strong

Particles vibrate in position

They have a fixed shape, cannot flow

Fixed volume

Question 22

Describe the composition of a liquid

Answer 22

Particles more spaced

Weaker inter-particle forces

Particles can slide over each other

No fixed shape

Fixed volume

Question 23

Describe the composition of a gas

Answer 23

Particles spread out

Inter-particle forces are negligible

Particles move freely

No fixed shape

No fixed volume

Question 24

Describe the kinetic theory of matter

Answer 24

It describes that the average kinetic energy of the particles is directly proportional to the temperature of the system. The state of matter at a given temperature and pressure is determined by the strength of forces that may exist between the particles, known as inter-particle forces.

Question 25

Fluids are solids, liquids or gases?

Answer 25

Liquids and gases - basically any substance that can flow and take the shape of their container.

Question 26

What is sublimation?

Answer 26

Solid to gas

Question 27

What is condensation

Answer 27

Gas to a liquid

Question 28

Liquid to a gas?

Answer 28

Evaporation

Question 29

Gas to solid?

Answer 29

Deposition

Question 30

Liquid to solid?

Answer 30

Freezing

Question 31

Gas to a liquid

Answer 31

Condensation

Question 32

Difference between evaporation and boiling?

Answer 32

Evaporation involves the change of a liquid to a gas but unlike boiling, evaporation occurs only at the surface and takes place at temperatures below the surface. Boiling on the other hand is when particles leave throughout the body of the liquid which is why the bubbles occur. Boiling occurs at a specific temperature, determined by when the vapour pressure reaches the external pressure.

Question 33

Describe the energy input and temperature graph

Answer 33

i) As the solid is heated, the vibrational energy of its particles increases and so the temperature increases
ii) This is the melting point. Vibrations are sufficiently energetic for the molecules to move away from their fixed positions and form a liquid. Energy added during this stage is used to break the inter-particle forces and NOT to raise the kinetic energy. Temperature stays constant
iii) As the liquid is heated, the particles gain kinetic energy and so the temperature increases
iv) This is the boiling point. Now there is sufficient energy to break all of the inter-particle forces and form a gas.
v) As the gas is heated under pressure, the kinetic energy of its particles continues to rise and so does temperature

PRESSURE REMAINS CONSTANT

Question 34

Describe the problems with the butane molar mass experiment

Answer 34

Butane can dissolve in the water, causing the Mr value to raise. Use colder water in which it is less soluble

Some air/water vapour can be collected with the gas, decreasing the Mr, use chilled boiled water to ensure less air is present

Butane gas escapes as the cylinder was tilted, causing molar mass to be greater because the decrease in mass of the lighter would be exaggerated.

Question 35

What could cause the Molar Mass of butane to be lower than expected

Answer 35

If pressure and volume are high.

Question 36

Describe the relationship between density and temperature

Answer 36

inversely proportional

Question 37

Does doubling temperature from 25 degrees to 50 degrees celcius change volume of a gas?

Answer 37

No, because when temperature is converted to kelvin, it is actually not doubled so volume does not double