The molar value of a gas - Higher
At a given temperature and Force exerted over an area. The greater the pressure, the greater the force exerted over the same area., one The amount of substance that contains the same number of particles as there are atoms in 12 g of carbon-12 (contains the Avogadro's constant 6.0 脳10虏鲁 number of particles). of any gas occupies the same The volume of a three-dimensional shape is a measure of the amount of space or capacity it occupies, eg an average can of fizzy drink has a volume of 330 ml.:
The The volume occupied by one mole of any gas (24 dm鲁 or 24000 cm鲁 at room temperature and pressure). is the volume occupied by one mole of any gas, at room temperature and pressure
The molar volume is equal to 24 dm3. This volume is given in questions that need it.
Calculating the amount of a gas
Question
Calculate the number of moles of helium atoms that occupy 36 dm3 at room temperature and pressure. (Molar volume = 24 dm3)
number of moles of gas = \(\frac{volume~of~gas~in~sample~(dm^3)}{24~(dm^3)}\)
=\(\frac{36}{24}\)
= 1.5 mol
Question
Calculate the number of moles of carbon dioxide molecules that occupies 120 cm3 at room temperature and pressure. (Molar volume = 24 dm3)
Always uses the same units as the molar volume:
120 cm3 = \(\frac{120}{1000}\)
= 0.12 dm3
number of moles of gas = \(\frac{volume~of~gas~in~sample~(dm^3)}{24~(dm^3)}\)
\(\frac{0.12}{24}\)
= 0.005 mol
Using the molar volume
Calculating the volume of a gas
The volume of a known In chemistry, a measure of the number of particles in a substance. of gas can be calculated by rearranging the equation to make volume the subject:
volume of gas (dm3) = number of moles x 24 dm3
Question
Calculate the volume of 0.25 mol of hydrogen gas at room temperature and pressure. (Molar volume = 24 dm3)
volume of gas (dm3) = number of moles x 24 dm3
= 0.25 脳 24
= 6 dm3
Question
Calculate the volume of 0.1 mol of oxygen gas at room temperature and pressure. (Molar volume = 24 dm3)
volume of gas (dm3) = number of moles x 24 dm3
= 0.10 x 24
= 2.4 dm3