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LC Chemistry > Gas Laws and the Mole > Flashcards

Gas Laws and the Mole Flashcards

1
Q

mole

A

The amount of a substance which contains 6.023 x 10²³ particles of that substance
(Avogadro’s number or constant = L)

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2
Q

kelvin

A

Celsius + 273

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3
Q

standard temp

A

273 K

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4
Q

normal temp

A

293 K

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5
Q

standard pressure

A

1 x 10⁵ Pa / 100,000 Pa

100 kPa

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6
Q

litre and cm³

A

1 litre = 1000 cm³

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7
Q

Boyle’s Law

A

States that: at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure

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8
Q

Charles’ Law

A

States that: at constant pressure, the volume of a fixed mass of a gas is directly proportional to its temperature measured on the Kelvin scale

V ∝ T

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9
Q

General Gas Law

A

hback

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10
Q

Gay Lussac’s Law of combining volumes

A

the volume of the reacting gases and the volumes of any gaseous products are in the ratio of small whole numbers provided the volumes are measured at the same temp + pressure

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11
Q

Avogadro’s Law

A

state that: equal volumes of gases contain equal numbers of molecules under the same conditions of temp + pressure

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12
Q

Molar Volume

A

at standard temp + pressure (s.t.p) one mole of any gas occupies 22.4 litres/dm³

at r.t.p: 24 litres/dm³

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13
Q

s.t.p

A

standard temperature + pressure

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14
Q

r.t.p

A

room temperature + pressure

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15
Q

Ideal Gas

A

one which perfectly obeys all the gas laws + all the assumptions of the kinetic theory of gases under all conditions of temperature + pressure

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16
Q

Gas

A

a substance that has no well defined boundaries but diffuses rapidly to fill any container in which it was placed

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17
Q

Pressure

A

The pressure of a gas is the force that the gas exerts on each unit area (eg. one square meter) of its container

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18
Q

Si unit of pressure

A

Newton per meter squared (N’m²)

Also called the pascal (Pa)

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19
Q

Normal atmospheric pressure

A

1 x 10⁵ N/m²

1 x 10⁵ Pa

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20
Q

Kilopascal

A

as numbers can be large, the kilo-pascal is also used

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21
Q

Volume

A

how much space something takes up

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22
Q

Si unit of volume

A

cubic meter (m³)

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23
Q

Gas & containers

A

volume of a sample of gas is same as container it is held in

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24
Q

Other ways volume is measured

A

cm³

litre (also known as dm³)

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25
Q

Pressure & volume

A

As pressure goes up, volume goes down

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26
Q

Pressure & temperature

A

as temperature (K) goes up, so does the pressure

27
Q

Pressure & temperature limitation

A

only works when temp is on Kelvin scale

28
Q

The Kinetic Theory of Gases - assumptions

A
  1. Gases made up of particles that are in continuous rapid, random motion, colliding w/ each other + walls of container
  2. No attractive or repulsive forces between particles of a gas
  3. Gas particles are so small + widely separated that total volume of all particles is negligible compared with space they occupy
  4. Collisions between particles are perfectly elastic, ie no overall loss of kinetic energy in these conditions
  5. Average kinetic energy of particles in a sample of a gas is proportional to temp measured on Kelvin scale
29
Q

The Kinetic Theory of Gases - limitations

A
  1. contrary to assumption 2, there are forces of attraction between particles of a gas
    eg. Van der Waals forces / Diople-dipole forces
  2. contrary to assumption 3, it is not valid to say that total volume of gas is always negligible compared with the space that they occupy
    - since these assumptions are not simply true, kinetic theory gases can only apply perfectly to what might be termed an ideal gas - no such gas exists
30
Q

gases deviate most from ideal behaviour when:

A
  • under high pressure (particles forced close together
  • at low temperature (particles moving slowly)
  • under these conditions, effect of inter-molecular fores becomes significant = volume of particles cannot be ignored when compared to volume in which they move
31
Q

gases come close to ideal behaviour when particles are separated from each other

A
  • low pressure
  • higher temperatures
  • majority of gases (under normal conditions) conform reasonably well to ideal behaviour
  • more the case w/ non-polar particles bc Van der Waals forces are relatively weak
32
Q

give 2 reasons why real gases depart from ideal behaviour

A

give 2 assumptions with limitations

eg. in an ideal gas, it is assumed that….
in real gases, ….

33
Q

one mole

A

6 x 10²³

34
Q

mass of one mole of an element

A

relative atomic mass in grams

35
Q

counting atoms

A

use moles

36
Q

Ideal gas law formula

A

pV = nRT

p = pressure (Pa)
V = volume (m³)
n = no. of moles
R = universal gas constant
T = temp (K)
37
Q

why real gases deviate from ideal behaviour at high pressure and low temperatures

A
  • molecules have non-negligible volume

- forces between molecules / molecules attract]repel one another

38
Q

Calculating no. of moles

A

n = m/Mr

39
Q

calculating mass in reaction

A

use n = m/Mr

40
Q

calculating volume of something at s.t.p

A

remember 1at standard temp + pressure (s.t.p) one mole of any gas occupies 22.4 litres,

so just multiply 22.4 by the no. of moles of that something

41
Q

calculating number of molecules produced in a reaction

A

multiply no. of moles by avogadro’s number (6x10²³)

1 mole of a substance has 6x10²³ molecules

42
Q

give one reason why a real gas like ammonia deviates from ideal behaviour

A

ammonia has intermolecular forces between mlecules

43
Q

equation of a state of an ideal gas

A

pV = nRT

p = Pa
V = m³
n = moles
R = universal gas constant
T = Kelvin
44
Q

1 litre in m³

A

1 litre = 0.001 m³

45
Q

to find the relative molecular mass of a gas

A

find the mass for 1 mole…

  • Find no of moles of gas and know/find the no. of grams of gas for that no. of moles
  • turn it into 1 mole to find the no. of grams for 1 mole.
46
Q

volatile liquid

A

a liquid with a low boiling point, or evaporates easily

47
Q

relative molecular mass

A

the mass of a molecule relative to the mass of 1/12 mass of the carbon-12 isotope

48
Q

experiment to determine relative molecular mass of a volatile liquid

A
  • incl diagram

- describe procedure

49
Q

how may pressure be measured

A

using a:

  • barometer
  • bourdon gauge
  • barograph
  • pressure sensor (not probe)
50
Q

activation energy diagram

A

must know

51
Q

what type of household product would you expect to find sodium hypochlorite

A

bleach / disinfectant

52
Q

Robert Boyle facts

A
  • Irish scientist
  • born 1627
  • son of the Earl of Cork
  • made Boyle’s law
53
Q

why carbon dioxide is more easily liquefied than helium

A

stronger intermolecular forces

54
Q

how many moles of gas are present in a sample containing 1.8 x 10²⁴ atoms of chlorine at s.t.p

A

1: divide 1.8 x 10²⁴ by 2, as Cl is diatomic

2. divide by Avogadro’s number (1 mole = 6 x 10²³ particles)

55
Q

how many atoms are present in 560 cm³ of ammonia at s.t.p

A

0.025 x 6 x 10²³ x 4

4, bc there are 4 atoms in ammonia (NH₃)

0.025 because

56
Q

dm³ and litre

A

1 dm³ = 1 litre

57
Q

suggest a way that further deterioration of a painting by this chem reaction could be prevented or delayed (bc of h2o)

A

keep it dry / low humidity / use waterproof varnish (coating)

58
Q

decimal point vs sig figure

eg. give 0.00494 correct to one sig figure

A

sig figure is any number not 0, decimal point is to do with placement

0.005

59
Q

note when using molar volume

A

ensure its in litres, eg. when turning volume to moles make sure volume is in litres before dividing by 22.4 or 24!!

60
Q

complete and balance the equation:

C2H5OH + Na –>

A

C2H5ONa + H2

then balance it

61
Q

“calculate total volume of the gaseous products”

A

Add up the volumes of the gaseous products at the end!!

62
Q

Expressing pressure in terms of atmospheres

A

1 atmosphere = 1x10^5 Pa,
so when you get the answer (Eg. 139675.2 Pa), round it up (depending on how many decimal points they want it in) eg. 140000 Pa, then express in atm
-> 1.4 atm

63
Q

Kp equil constant eg.

A

Kp = (Pₚᵣₒ𝒹ᵤ𝒸ₜ ₁)(Pₚᵣₒ𝒹ᵤ𝒸ₜ ₂)/(Pᵣₑₐ𝒸ₜₐₙₜ)

LC Chemistry (26 decks)

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