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Mole: A mole is define as the amount of substance that contain 6.02 x 10^23 particles

Molar Volume

Avogadro’s Hypothesis

Equal volumes of all gases under the same conditions of temperature and pressure contain equal number of molecules.

Therefore, 1 mole of any gas will always occupy the same volume (at a constant temperature and pressure).

This is what is called molar volume. It is the volume occupied by one mole of gas.

Molar volume only applies to gases. The value means nothing if the temperature and pressure are not stated (must be the same to compare).

Standard Temperature and Pressure (STP) (at sea level)

T=0°C P=101.3kPa V=22.4L Molar volume (of any gas) = (numerator and dominator refer to the same gas)

Standard Ambient Temperature and Pressure (STP) T=25°C



Molar volume (of any gas) = 22.4 L

Note: Molar volume is just another conversion to moles. It allows us to convert the volume of a gas to moles.


water Molecules loosely bounded to a compound

Note: Heating hydrate will evaporate water and leave you with anhydrous compound (or compound without water)

Molecular Formula

Formula that gives the actual number of atoms in the compound. Example: C6H6 vs CH

Note: Empirical Formula: gives the simplest whole number ratio of elements in a compound Example: CH

Method of Finding Molecular Formula: Step 1: Find the mass of each element

Step 2: Find the moles of each element

Step 3: Find the Empirical formula of the compound

Step 4: use Molar mass of the molecular formula and the molar mass of the Empirical formula to find the mole ratio of each element.

Empirical Formula

Method of Finding Empirical Formula

Step 1: Find the mass of each element

Step 2: Find the moles of each element

Step 3: Find the ratios among elements