Slide 3 of 14
• The combined gas law:– The three gas laws can be combined into one
law– The combined gas law allows you to do
calculations for situations in which only the amount of gas is constant.
– Equation:
Slide 4 of 14
• Describe the ideal gas law and use it to calculate the value of an unknown.
• Compare and contrast ideal and real gases.
Slide 5 of 14
• The ideal gas law– Takes into account the amount of gas ( in
moles)– n = number of moles– # moles is proportional to volume so:
Slide 6 of 14
• The ideal gas constant was calculated using the volume of 1 mole of gas at STP. The symbol for the gas constant is R
Slide 8 of 14
• The ideal gas law allows you to solve for the number of moles if P, V and T are known.
– (R= 8.31 L ∙ kPa / K ∙mol)
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• A steel cylinder with a volume of 20.0 L is filled with nitrogen gas to a final pressure of 20 000.0 kPa at 27 °C. How many moles of N2
does the cylinder contain?
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• When a closed container of 680 L of He gas are heated from 300 K to 600 K the pressure of the gas increases to 1800 kPa. How many moles of He are in the container?
Slide 11 of 14
• Real gases– Do not behave exactly like “ideal” gases: they
may condense at low temperatures– Real gases differ most from ideal gases at low
temperatures and high pressure
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Ideal Gases >14.3 Ideal Gases and Real Gases
A gas can condense,or even solidify, when it is compressed or cooled.