States that under equal conditions of temperature and
pressure, equal volumes of gases contain an equal number
of molecules.

Aug. 2003 #20. At the same temperature and pressure,
1.0 liter of CO(g) and 1.0 liter of CO2(g) have

A. equal masses and the same number of molecules
B. different masses and a different number of molecules
C. equal volumes and the same number of molecules
D. different volumes and a different number of molecules

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C

Jan. 2010# 22 Which rigid cylinder contains the same number of
gas molecules at STP as a 2.0-liter rigid cylinder containing H_{2(g)}
at STP?
(1) 1.0-L cylinder of O_{2(g)}
(2) 2.0-L cylinder of CH_{4(g)}
(3) 1.5-L cylinder of NH_{3(g)}
(4) 4.0-L cylinder of He_{(g)}

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2

Jan 2009 #17 Which two samples of gas at STP contain the same
total number of molecules?
(1) 1 L of CO_{(g)} and 0.5 L of N_{2(g)}
(2) 2 L of CO_{(g)} and 0.5 L of NH_{3(g)}
(3) 1 L of H_{2(g)} and 2 L of Cl_{2(g)}
(4) 2 L of H_{2(g)} and 2 L of Cl_{2(g)}

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4

Jan 2002
15 At the same temperature and
pressure, which sample contains the same
number of moles of particles as 1 liter of O_{2}(g)?

(1) 1 L Ne(g) (3) 0.5
L SO_{2}(g)
(2) 2 L N_{2(}g) (4) 1 L H_{2}O(ℓ)

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1

Molar Volume of a Gas

This hypothesis was not acknowledged in Avogadro's
lifetime and it wasn't until Stanislao Cannizzaro, in
1860, demonstrated that it was the solution to the
problem of atomic and molecular weights that Avogadro's
Law became widely accepted. The number of particles in
one mole of a substance was named Avogadro's number in
his honor, and is numerically equal to 6.02252 x 10 ^{23}

Avogadro’s law, which is
derived from this basic idea, says that the volume of a
gas maintained at constant temperature and pressure is
directly proportional to the number of moles of the gas,
or

V
= constant x n (where n is the number of
moles of the gas)

which can be rearranged thus:

P = the gas absolute pressure, in atm

n = number of moles, in mol

V = the volume, in L

T = the gas absolute temperature, in K

R = the universal gas law constant of 0.0821 L·atm/(mol·K)

1 mole of gas is
calculated to be 22.4L/mole of a
gas @STP.