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4S6Welcome To my Chemistry Class~
Number of particles
Number of
Moles
Avogadro
constant
(Mary No Car)
1. Number Of Particles = number of moles x Avogadro constant
2. Number Of Moles = number of particles ÷ Avogadro constant
Particles= Atoms, molecules, ions
Avogadro constant = 6.02 x 1023
RECALL BACK….
1 mole of Carbon = 6.02 x 1023 atoms 1 mole of H20 = 6.02 x 1023 molecules 1 mole of Fe2+ = 6.02 x 1023 ions 1 mole of O2 = 6.02 x 1023 molecules
= 2 x 6.02 x 1023 atoms
CALCULATE THE NUMBER OF ATOMS IN 3 MOL OF COPPER ATOMS.
Number of Atoms= Number of mole x Avogadro Constant
= 3 x 6.02 x 1023
= 1.806 x 1024 mol of copper atoms
Cu
CALCULATE THE NUMBER OF MOLECULE IN 0.5 MOL OF CO2
Number of molecule= Number of mole x Avogadro Constant
= 0.5 x 6.02 x 1023
= 3.01 x 1022 mol of carbon dioxide
C
O
O
Number of ions= Number of mole x Avogadro Constant
= 0.4 x 6.02 x 1023
= 2.408 x 1022 mol of Pb2+
Calculate the number of Ions in 0.5 mol of Pb2+ Pb2
+
CALCULATE THE NUMBER OF ATOMS IN 0.5 MOL OF CO2
Number of atoms= Number of mole x Avogadro Constant
= 3 x 0.5 x 6.02 x 1023
= 9.03 x 1023 mol of carbon dioxide
atoms
C
O
O
EXAMPLE 2:
a. Calculate the number of moles of atoms in 1.204 x 1025 iron atoms.
b. Calculate the number of moles of ions in 6.02 x 1021 copper(II) ions, ____
c. Given 1.505 x 1024 oxygen gas, , calculate i) the number of moles of oxygen
molecules, ii) the number of atoms of oxygen atomsd. Given 2.408 x 1025 hydrogen atoms,
calculate i) the number of moles of hydrogen atoms. ii) the number of moles of hydrogen
molecules,
A. CALCULATE THE NUMBER OF MOLES OF ATOMS IN 1.204 X 1025 IRON ATOMS.
Number of Moles= Number of particles Avogadro Constant
= 1.204 x 1025
6.02 x 1023
= 20 mol of iron atoms
B. CALCULATE THE NUMBER OF MOLES OF IONS IN 6.02 X 1021 COPPER(II) IONS, ____
Number of Moles= Number of particles Avogadro Constant
= 6.02 x 1021
6.02 x 1023
= 0.01 mol of copper(II) ions
C. GIVEN 1.505 X 1024 OXYGEN GAS, , CALCULATE I) THE NUMBER OF MOLES OF OXYGEN MOLECULES,
Number of Moles= Number of particles Avogadro Constant
= 1.505 x 1024
6.02 x 1023
= 2.5 mol of Oxygen molecules
C. GIVEN 1.505 X 1024 OXYGEN GAS, , CALCULATE
II) THE NUMBER OF ATOMS OF OXYGEN ATOMS
2 x 1.505 x 1024
= 3.01 x 1024 oxygen atoms
O
O
1 O2 molecule = 2 O atoms
OO
O
OO
O
D. GIVEN 2.408 X 1025 HYDROGEN ATOMS, CALCULATE I) THE NUMBER OF MOLES OF HYDROGEN ATOMS. II) THE NUMBER OF MOLES OF HYDROGEN MOLECULES,
i) Number of Moles= Number of particles Avogadro Constant
= 2.408 x 1025
6.02 x 1023
= 40 mol of hydrogen atoms
ii) 40 mol of hydrogen atoms
= 40 ÷ 2
= 20 mol of hydrogen molecules
H
H
H
H
NOTE:
The gases which exist as diatomic molecules are:
O2 H2 Cl2 Br2N2 I2
O
O
HH
ClCl
I I
3.3 THE MOLE AND THE MASS OF SUBSTANCES
A. The molar mass - is the mass of one mole of any
substance. The molar mass of a substance = the mass
of _______ of substance = the mass of ____________ particles.
-the unit of molar mass is ________. 1 mol of carbon-12 has a mass of exactly
_____g. So, the molar mass of carbon-12 is
__________.
1 mole
12
12
THE MOLAR MASS OF ALL THE OTHER SUBSTANCES ARE NUMERICALLY EQUAL TO THEIR RELATIVE MASSES.
Examples: The relative atomic mass of sodium = 23, so,
the molar mass of sodium = ____________ The relative atomic mass of water, so, the
molar mass of water = ____________
23
18
(Mario Miss Rainbow)
Mass
Number of
Moles
Relative atomic Mass/ RMM
EXAMPLE 1:
a. Calculate the mass of 2 mol of carbon atoms
b. Calculate the mass of 5 mol of oxygen gas, c. calculate the mass 0.4 mol of magnesium
oxide, MgO.
CALCULATE THE MASS OF 2 MOL OF CARBON ATOMS
The molar mass of carbon atoms = 12gmol-1
so, the mass of 2 mol of carbon atoms= 2 mol x 12gmol-1
= 24g
CALCULATE THE MASS OF 5 MOL OF OXYGEN GAS
the mass of 5 mol of oxygen gas= 5 mol x 32gmol-1
= 160g
The molar mass of MgO = 24+16 = 40gmol-1
The mass of 0.4 mol of magnesium oxide= 0.4 mol x 40gmol-1
= 16g
Calculate the mass 0.4 mol of magnesium oxide, MgO.
ANSWER
a) The molar mass of carbon atoms = 12gmol-1
so, the mass of 2 mol of carbon atoms= 2 mol x 12gmol-1
= 24gb) The molar mass of oxygen gas = 2(16) = 32gmol-1
so, the mass of 5 mol of carbon atoms=5 mol x 32gmol-1
= 160g
c) The molar mass of MgO = 24+16 = 40gmol-1
so, the mass of 0.4 mol of MgO = 0.4 mol x 40gmol-1
= 16g
EXAMPLE 2:
a. How many moles of atoms are there in 18g of carbon?
b. How many moles of sodium chloride are there in 14.625g of sodium chloride, NaCl?
c. Given 6.4g of oxygen gas, calculate i) the number of moles of oxygen gas. ii) the number of moles of oxygen atoms.
The molar mass of carbon atoms = 12gmol-1
The number of moles of carbon atoms = 18 g 12gmol-1
= 1.5mol
How many moles of atoms are there in 18g of carbon?
The molar mass of sodium chloride, NaCl = 23 + 35.5=58.5gmol-1
So, the number of moles of NaCl =14.635 g 58.5gmol-1
=0.25mol
How many moles of sodium chloride are there in 14.625g of sodium chloride, NaCl?
The molar mass of Oxygen gas = 2(16) = 32gmol-1
So, the number of moles of oxygen gas = 6.4 g 32gmol-1
= 0.2mol
Given 6.4g of oxygen gas, calculate
i) the number of moles of oxygen gas.O
O
II) THE NUMBER OF MOLES OF OXYGEN ATOMS.
ii) The number of moles of oxygen atoms = 2 x 0.2 mol = 0.4 mol
O
O
ANSWER:
a) The molar mass of carbon atoms = 12gmol-1
The number of moles of carbon atoms = 18 g 12gmol-1
= 1.5molb) The molar mass of sodium chloride, NaCl = 23 + 35.5 = 58.5gmol-1
So, the number of moles of carbon atoms=14.635 g 58.5gmol-1
= 0.25molc) i) The molar mass of Oxygen gas = 2(16) = 32gmol-1
So, the number of moles of oxygen gas = 6.4 g 32gmol-1
= 0.2mol ii) The number of moles of oxygen atoms
= 2 x 0.2 mol = 0.4 mol
EXAMPLE 3:
a. Calculate the mass of 6.02x 1021 iron atoms.
b. How many molecules of oxygen are there in 12.8 g of oxygen gas?
Number of moles= 6.02 x 1021
6.02 x 1023
= 0.01 mol The mass of 6.02x 1021 iron atoms= 0.01mol x 56gmol-1 = 0.56g
a. Calculate the mass of 6.02x 1021 iron atoms. Fe
Number of moles= 12.8 g 32gmol-1 = 0.4 molNumber of molecule of oxygen= 0.4 x 6.02 x 1023
= 2.408 x 1023 molecules of oxygen
How many molecules of oxygen are there in 12.8 g of oxygen gas?
O
O
ANSWER:
a. 6.02 x 1021 iron atoms = 6.02 x 1021
6.02 x 1023
= 0.01 mol 0.01 mol of iron atoms = 0.01mol x 56gmol-1 =
0.56g
b) 12.8g of oxygen gas = 12.8 g 32gmol-1 = 0.4 mol
0.4mol of oxygen gas = 0.4 x 6.02 x 1023
= 2.408 x 1023 molecules of
oxygen
PASS UP THURSDAY(28/2/2013)
Cl-
Zn2+
Cl-
1 Zn2+ ion 2 Cl- ions1 ZnCl2 =
