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Chemistry (Tara) > The gas laws > Flashcards

The gas laws Flashcards

1
Q

Do gases have a fixed volume?

A

no

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2
Q

diffusion

A

the spreading out of a gas to fill a space

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3
Q

how do you demonstrate diffusion

A

cotton wool, one end soaked in HCl solution and the other in NH3 solution. ring of ammonium chloride forms between them

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4
Q

do the solutions move at the same rate in diffusion?

A

no, the lighter one generally moves faster

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5
Q

if temperature increases what happens to a gas

A

it expands

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6
Q

if pressure increases what happens to a gas

A

it is compressed, smaller volume

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7
Q

Boyle’s law

A

when a fixed mass of gas is kept at constant temperature, it’s volume multiplied by it’s pressure is constant

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8
Q

mathematical expression of Boyle’s law

A

p1V1 = p2V2

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9
Q

graph of boyles law, volume vs pressure, y axis

A

volume (cm cubed)

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10
Q

graph of boyles law, volume vs pressure, x axis

A

pressure (Pa)

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11
Q

how do you show that pressure is inversely proportional to volume

A

draw a graph of pressure vs 1/volume

straight line through the origin

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12
Q

Boyle’s law is true for all gases provided that..

A

the same units were used on both sides of the equation

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13
Q

graph of pV vs p

A

straight line horizontally

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14
Q

Charles’ law

A

the volume of a fixed mass of gas, kept at constant pressure, is directly proportional to the absolute temperature

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15
Q

absolute temperature

A

temperature measured in kelvin

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16
Q

how do you get from ºc to K

A

add 273.15

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17
Q

how do you get from K to ºc

A

take away 273.15

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18
Q

where is the origin on the graph of volume vs temperature

A

0K (not 0ºc)

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19
Q

mathematical expression of Charles’ law

A

V1/T1 = V2/T2 where T is measured in kelvin

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20
Q

graph of V/T against T

A

straight horizontal line

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21
Q

Gay-Lusaac’s law of combining volumes

A

volumes of gases always react with each other in simple whole number ratios when the volumes are measured at the same temperature and pressure

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22
Q

2 conditions for Gay-Lusaac’s law of combining volumes

A

everything has to be gaseous

same temperature and pressure

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23
Q

when can you not use moles when doing calculations

A

if everything is gaseous

same temperature and pressure

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24
Q

Avogadro’s law

A

equal volumes of gases measured under the same conditions of temperature and pressure contain equal numbers of molecules

25
for Gay-Lusaac's law of combining volumes and avogadro's law, does it have to be stp?
no just the same temperature and pressure, not just standard
26
first words of Gay-Lusaac's law of combining volumes
volumes of gases
27
first words of Avogadro's law
equal volumes of gases
28
The combined gas law // the general gas law
P1V1/T1 = P2V2/T2 temperature and pressure
29
what does the combined gas law // the general gas law come from
boyle's and charles' laws
30
where does avogadro's law come from
Gay-Lusaac's law of combining volumes
31
5 assumptions made by the kinetic theory of gases about gases
1. their particles are widely separated, their volume is mostly empty space and do not occupy much space 2. their particles are in constant random motion colliding with each other and walls of the container 3. the collisions are elastic, no loss of energy as a result 4. their particles are independent of each other. no attractive forces between them 5. the average kinetic energy of the particles is proportional to the absolute temperature
32
3 reasons why ideal gases do not exist
+ there are attractive forces (VdW) + the amount of space occupied is significant especially under high pressure + collisions are not all perfectly elastic as energy can be lost to surroundings
33
ideal gas
a gas that obeys all gas laws at all temperatures and pressures
34
when do real gases come closest to ideal behaviour
at low pressures and at high temperatures
35
under normal conditions
real gases behave similarly to ideal gases
36
3 reasons why real gases depart from ideal behaviour
+ there are forces of attraction between molecules + the amount of space occupied is significant especially under high pressure + collisions are not all perfectly elastic as energy can be lost to surroundings
37
the equation of state for an ideal gas
PV = nRT
38
P
pressure in Pa or N/m squared
39
V
volume in m cubed
40
R
gas constant
41
T
temperature in kelvin
42
n
moles
43
how to get from KPa to Pa
multiply by 10 ³
44
how to get from cm cubed to m cubed
multiply by 10^-6
45
how to get from L to m cubed
multiply by 10-³
46
how to get from ºc to K
+ 273.15
47
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | 8 pieces of apparatus
graduated gas syringe, hypodermic syringe, thermometer, container with steam inlet, self sealing rubber cap, electronic balance
48
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | material
a volatile liquid - propanone
49
propanone
CH3COCH3
50
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | first step
draw about 5cm³ of air into graduated gas syringe and place rubber cap on
51
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | after you put air into the graduated syringe
pass steam through the container until volume of air and temperature are steady and note these values
52
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | after you have noted values for temperature and volume
draw propanone into the hypodermic syringe and note the mass using an electronic balance
53
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | after propanone is in syringe and mass recorded
push the hypodermic syringe through the rubber cap and inject half of the propanone in
54
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | once propanone has been injected into the setup
note the plunger of the graduated cylinder moving out and note the new volume reading
55
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | once the new volume reading is noted
withdraw the hypodermic syringe and rerecord the mass
56
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | atmospheric pressure at the end
noted on the barometer
57
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | volume of vapour
final - initial
58
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | mass of vapour
initial - final
59
DETERMINING THE Mr OF A VOLATILE LIQUID USING A GAS SYRINGE | 3 sources of error
accuracy of measuring instruments eg. mass balance air bubbles in hypodermic syringe there is no such thing as an ideal gas and we use the ideal gas equation to calculate this

Chemistry (Tara) (50 decks)

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