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Chemistry Unit 2 > Gases > Flashcards

Gases Flashcards

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1
Q

what gases are in our atmosphere?

A
  • There are many gases in our atmosphere.
  • Some of these gases are greenhouse gases. These are gases that are able to absorb infrared radiation from the sun.
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2
Q

what gases in the atmosphere are not greenhouse gases?

A

N2, O2

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3
Q

what gases in the atmosphere are greenhouse gases?

A

CO2, CH4, H2O
NB: H2O contributes to the greenhouse effect when in gas state, not liquid state

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4
Q

what is the Natural greenhouse effect?

A
  • When CO2, CH4, H2O absorb infrared radiation, some of this light becomes trapped in the atmosphere in the form of heat, warming the Earth.
  • Some amount of greenhouse effect is essential for life. Without this effect its estimated the Earth’s temperature would be -5oC.
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5
Q

what has lead to the Enhanced greenhouse effect?

A

Human activity has lead to the enhanced greenhouse effect.

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6
Q

what is the Enhanced greenhouse effect?

A

We have created an excess of greenhouse gases in the atmosphere, increasing the warming effect of the atmosphere.

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7
Q

what is the most prominent greenhouse gas in our atmosphere?

A

Water is actually the most prominent greenhouse gas in our atmosphere.

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8
Q

why isn’t water talked about as a greenhouse gas as much as others?

A

However, because water naturally cycles through the atmosphere, it is often not considered when we think about human activities that contribute to the enhanced greenhouse effect.

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9
Q

where do Green house gas emissions come from?

A
  • Agriculture
  • Forestry
  • Industry
  • Energy supply
  • Waste and waste water
  • Transportation
  • Commercial buildings
  • Residential buildings
  • Electricity supply
  • Heat supply
  • Livestock
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10
Q

4 key variables when looking at gases?

A
  • Pressure (P)
  • Volume (V)
  • Temperature (T)
  • Moles (n)
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11
Q

what is pressure for gases?

A

no. of collisions between gas particles and walls of container

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12
Q

what is volume for gases?

A

size of container gas is in

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13
Q

what is temperature for gases?

A

average temp. of gas particles (temp directly affects the speed that gas particles move around at)

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14
Q

what is moles for gases?

A

no. of moles of gas particles

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15
Q

why are these variables important?

A

These variables are important because changes in one variable, results in changes in the others.

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16
Q

relationship between Temp. and Pressure?

A

directly proportional

17
Q

relationship between Temp. and Volume?

A

directly proportional

18
Q

relationship between Volume. and Pressure?

A

inversely proportional

19
Q

relationship between Moles and Pressure?

A

directly proportional

20
Q

what can Universal gas law be used for?

A
  • Can only be used for gases, not solids or liquids.
  • Can be used for a gas under any conditions.
21
Q

what is Universal gas law?

A

PV=nRT

22
Q

variables and units in Universal gas law?

A

P = pressure (kPa)
V = volume (L)
n = moles (mol)
R = gas constant = 8.31
T = temp (K) NB: add 273 to your °C

23
Q

what amount of space do gases occupy?

A

Most of the volume a gas occupies is empty space, as such,
1 mole of any gas (independent of which one) will always occupy the same volume.

24
Q

what volume do gases take up at SLC?

A

When the gas is at standard lab conditions (SLC) this volume = 24.8L

25
Q

what is SLC?

A
  • 25oC (298 K)
  • 100 kPa
26
Q

do you need to use Universal gas law at SLC?

A

If your gas is at SLC, the temp. and pressure are known, hence you don’t need to use pV = nRT.
- Instead use this simplified version:
n = V/VM
VM = 24.8L

27
Q

when are gases considered ideal?

A

Gases are considered “ideal” when their behaviour mirrors that proposed by kinetic molecular theory. Gases are almost never truly “ideal”.

28
Q

what formulas apply when gases are ideal?

A

Assuming gases behave ideally, the formulas pV=nRT and n=V/VM apply.

29
Q

when are gases not ideal?

A

When gases are at very low temperature or very high pressures, their behaviour deviates significantly from kinetic molecular theory and the ideal gas laws/relationships no longer apply.

30
Q

what is pressure given in?

A

In some cases pressure may not be given in kPa (which is needed for pV = nRT).

31
Q

what is 1000 Pa in kPa?

A

1 kPa

32
Q

what is 0.987 atm in kPa?

A

100 kPa

33
Q

what is 750 mm Hg in kPa?

A

100 kPa

Chemistry Unit 2 (5 decks)

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