Upload
others
View
2
Download
0
Embed Size (px)
Citation preview
Atomic mass and the mole conceptp. 245
MOL is the SI unit for amount of substance(amount of matter).
There are 6,02 x 1023 atoms in 12 g of carbon-12.
Avogadro’s constant (NA)
One mole is the amount of matter containing the same number of particles as there are atoms in 12 g of carbon-12.
Avogadro’s number, NA, is the number of particles (atoms, molecules, formula units) present in one mole (NA = 6,023 x 1023 mol-1).
One mole of atoms is 6,02 x 1023 atoms
One mole of ions is 6,02 x 1023 ions
One mole of molecules is 6,02 x 1023 molecules
How many atoms are in 1 mole of argon atoms?
6,02 x 1023 atoms
How many molecules are in 1 mole of HCℓ molecules?
6,02 x 1023 molecules
How many atoms are in 1 mole of HCℓ molecules?
2 x 6,02 x 1023 atoms
How many hydrogen atoms are in 1 mole of HCℓ molecules?
6,02 x 1023 H atoms
How many chlorine atoms are in 1 mole of HCℓ molecules?
6,02 x 1023 Cℓ atoms
How many chlorine molecules are in 1 mole of Cℓ2 molecules?
6,02 x 1023 Cℓ2 molecules
How many chlorine atoms are in 1 mole of Cℓ2 molecules?
2 x 6,02 x 1023 Cℓ atoms
How many water molecules are in 1 mole of H2O molecules?
6,02 x 1023 H2O molecules
How many atoms are in 1 mole of H2O molecules?
3 x 6,02 x 1023 atoms
How many H atoms are in 1 mole of H2O molecules?
2 x 6,02 x 1023 H atoms
How many O atoms are in 1 mole of H2O molecules?
6,02 x 1023 O atoms
Relative atomic mass is the mass of an atom ona scale where a carbon-12 atom has a mass of 12.No unit.
Molar mass is the mass of one mole of a substance measured in g·mol-1.
Homework
p. 249
nos. 2, 6.1, 6.2, 6.3, 7, 8
2. What are the approximate relative atomic masses (Ar) of the following atoms?
HydrogenCalciumHeliumIronCopperChlorine
14045663,535,5
6.1 Calculate the relative molecular formula mass (Mr) of the following substances:
C2H6
Mr(C2H6) = (2 x 12) + (6 x 1)= 30
6.2 Calculate the relative molecular formula mass (Mr) of the following substances:
Na2SO3
Mr(Na2SO3) = (2 x 23) + (32) + (3 x 16)= 126
6.3 Calculate the relative molecular formula mass (Mr) of the following substances:
K2Cr2O7
Mr(K2Cr2O7) = (2 x 39) + (2 x 52) + (7 x 16)= 294
7. Nitrogen forms a compound with molecular formula NxO4. The relative molecular mass of the compound is 92. What is the ...
(1) value of x? (2) correct formula for NxO4?
Mr(NxO4) = (x x 14) + (4 x 16) = 9214x + 64 = 92
14x = 28x = 2
Thus: N2O4
8. Four nitrogen atoms have the same mass as one formula unit of the ionic substance XO. Which element is X on the Periodic Table?
Mr(XO) = (x x 1) + (1 x 16) = (4 x 14)x + 16 = 56
x = 40
Thus: Element X is Ca → CaO