Molar Volume Flashcards

All 5 cards in this deck

What is the molar volume of a gas at room temperature and pressure?

$24\ \mathrm{dm^3}$ ($24\,000\ \mathrm{cm^3}$) — the volume occupied by one mole of molecules of any gas at rtp.

What is the formula linking the volume of a gas at rtp to the number of moles?

e.g. $0.50$ mol of carbon dioxide

volume in $\mathrm{dm^3}$ = moles $\times 24$
$= 0.50 \times 24 = 12\ \mathrm{dm^3}$

What are the steps to find the number of moles in a measured volume of gas at rtp?

e.g. $480\ \mathrm{cm^3}$ of hydrogen

1. Use moles = volume $\div$ molar volume, in matching units
2. $480 \div 24\,000 = 0.020$ mol

What are the steps to find the volume of gas produced from a mass of solid?

e.g. $10\ \mathrm{g}$ of CaCO$_3$ ($M_r = 100$) decomposing: $\mathrm{CaCO_3 \rightarrow CaO + CO_2}$

1. Moles of solid = mass $\div M_r$ = $10 \div 100 = 0.10$ mol
2. Use the equation ratio (1 : 1): moles of CO$_2$ = $0.10$ mol
3. Volume = moles $\times 24 = 0.10 \times 24 = 2.4\ \mathrm{dm^3}$

True or false? At rtp, one mole of carbon dioxide occupies a larger volume than one mole of hydrogen.

False. One mole of any gas occupies the same volume, $24\ \mathrm{dm^3}$, at rtp.