Unit 5 Part 7 Moles Grams And Liters

Part 7 – Moles into Grams and Liters

WEIGHING (MASSING) IN CHEMISTRY• Chemists use mass, and normally small

masses such as grams.

• However they must relate the mass of chemical back to the counting of individual atoms.

The Gram Atomic Mass (GAM)• gram atomic mass- the mass of one

mole of an element.

• The gram atomic mass numerically equals the atomic mass of the element in grams.

Example:

• Find the gram atomic mass of the following elements: – Na, Hg, Fe, S

Gram Formula Mass (GFM)

• gram formula mass- the mass of one mole of a compound.

• For gram formula mass we add together the gram atomic masses of the elements which make up the compound.

Example

• Find the gram formula mass of the following compounds: – CoCl2 , H2O, H2S04

• Name these compounds.

Converting between moles and grams of a substance.• Conversions between moles and the

mass of a substance uses the gram atomic mass or gram formula mass.

To convert from moles to grams• 1. Find the gram formula mass of the

compound or element your looking for.

• 2. Determine the number of moles you were given.

• 3. Multiply the number of moles by the gram formula mass.

Example

• Find the mass of 0.160 mol H2O2.

• Find the mass of 6.0 X 1026 atoms of Be.

To convert from grams to moles• 1. Find the gram formula mass of the

compound you are looking for.

• 2. Determine the number of grams you were given.

• 3. Divide the number of grams you were given by the gram formula mass.

Example

• Find the number of moles in each of the following:– 333g SnF2.

– 5.0 X 1024 molecules of SnF2.

Try these on you own...

• Find the mass in each of the quantities below

– 10.0 mol Cr

– 3.32 mol K– 2.4 mol N2

• Find the number of moles in each of the quantities below

– 10g H2O2

– 15g Ca(NO3)2

– 50g C20H42

FINDING VOLUME IN CHEMISTRY

The Volume of a mole of gas

• Although the volumes of 1 mol of a liquid or solid can vary greatly between different substances, the volume of 1 mol of the gas of any substance has the same volume, at equal temperature and pressure.

• 1 mole of a gas of any substance occupies a volume of 22.4L at STP (standard temperature and pressure).

Standard Temperature and Pressure (STP)• Temperature and pressure can affect

the volume of a gas.

• In order to “standardize” experiments between scientist, we use a standard set of values to work with gases.

• Standard Temperature = 0°C

• Standard Pressure = 1 atm (air pressure at sea level)

Examples

• Determine the volume, in liters, of 0.600 mol of SO2 gas at STP.

Your turn…

• What is the volume at STP of 0.960 mol CH4?

• Assuming STP, how many moles are in 89.6 L SO2?

Converting between units with moles• The mole is the most useful way for

chemists to express the amount of matter.

Try these...

• Determine the volume in liters of 50g of SO2 gas at STP.