Chemical Quantities

Ways to measure matter:
 Count how many of something you have
 Weigh it (or mass it)
 Volume
Units that refer to a specific #
 pair = 2
 dozen = 12

1 mole = 6.02 x 1023 atoms,
molecules, ions, formula units

A.k.a. Avogadro’s Number

1 mole of a substance contains 6.02 x
1023 representative particles
Representative particle: refers to the species
present in a substance: atoms, molecules,
ions
Substance
Atomic N
Nitrogen Gas
Water
Calcium ion
Calcium
flouride
Sucrose
Rep. Particle
Atom
Molecule
Molecule
Ion
Formula unit
Formula
N
N2
H2O
Ca+2
CaF2
R.P. in 1 mol
Molecule
C12H22O11
6.02 * 1023
6.02 * 1023
6.02 * 1023
6.02 * 1023
6.02 * 1023
6.02 * 1023

How big is one mole?
 One mole of sand would cover L.A. to a
depth of 600 meters (1,968 ft)

Marbles would cover the earth to a
depth of 40 miles

Propane is a gas used for cooking and heating.
How many atoms are in 2.12 mol of propane
(C3H8)?



Atomic mass unit of all elements are based off
the Carbon – 12 atom
The atomic mass of an element expressed in
grams is the mass of a mole of the element
How many atoms are in one mole of
magnesium?


To calculate the molar mass of a compound,
find the number of grams of each element in
one mole of the compound. Then add the
masses of the elements in the compound
What is the molar mass of CO2
conversions


Grams A 1 mole A = mole A
gfm A
Mole B
gfm B = gfm B
1 mole B

Avogadro’s Hypothesis – equal volumes of
gases at the same temperature and pressure
contain equal numbers of particles

Standard temperature and pressure – (STP)
Standard temp: 0oC
pressure: 101.3 kPa or 1 atm
@ STP 1 mole of gas occupies 22.4 L

22.4 L = molar volume of a gas @ STP

END of Part 3


Molar mass = density @ STP x molar volume @
STP
The density of a gas containing Carbon and
Oxygen is found to be 1.946 g/L @ STP. What
is the molar mass of the compound?


The relative amounts of the elements in a
compound are expressed as percent
composition
The percent by mass of an element in a
compound
- the number of grams of the element divided by the
mass in grams of the compound...multiplied by
100%.

Calculate the percent composition of Carbon
and Hydrogen in propane (C3H8).

Empirical formula: gives the lowest whole
number ratio of the atoms of the elements in a
compound
What is the empirical formula of a compound that
is 67.6% mercury, 10.8% sulfur and 21.6%
oxygen?

What is the empirical formula of a compound
that is 25.9% nitrogen and 74.1% oxygen?

END of Part 4