calculating relative atomic mass - answers included
TRANSCRIPT
Calculating Relative
Atomic Mass
Relative atomic mass
Standard atomic weight
Average mass of an atom within a sample
Average mass of an atom within a normal sample
Cl 35
17 Cl 37
17
Relative atomic mass (atomic weight)
abundance
# isotopes
atomic mass
In a given sample of 20,000 chlorine atoms, there are two isotopes: chlorine-35 (15,106, 34.97 u) and chlorine-37 (4,894 , 36.97u). What is the relative atomic mass?
15,106 4,894
34.97 36.97
= (N1 x Ma1) + (N2 x Ma2) number of atoms
= 35.459
= (15,106 x 34.97) + (4,894 x 36.97) (15,106 + 4,894)
= 528,256.82 + 180,931.18 20,000
= 70,9188 20,000
or 35.46
Standard atomic weight = 35.45
Br 81
35 Br 79
35
Relative atomic mass (atomic weight)
abundance
# isotopes
atomic mass
In a given sample of bromine atoms, 20% of atoms are bromine-81 atoms (80.92u) and 80% are bromine-79 atoms (78.92u). What is the relative atomic mass?
20% 80%
80.92 78.92
= (F1 x Ma1) + (F2 x Ma2)
= 79.32
= (0.20 x 80.92) + (0.80 x 78.92)
= 16.184 + 63.136
or 79
Standard atomic weight = 79.9
Ti 46
22 Ti 47
22
Relative atomic mass (atomic weight)
abundance
# isotopes
atomic mass
In a given sample of titanium atoms, 8.0% of atoms are titanium-46 atoms (45.95u), 7.3% are titanium-47 atoms (46.95u), 73.8% are titanium-48 atoms (47.95), 5.5% are titanium-49 atoms (48.95u), and 5.4% are titanium-50 atoms (49.94). What is the relative atomic mass?
8.0% 73.8%
45.95 47.95
= (F1 x Ma1) + (F2 x Ma2)
= 47.87946
= (0.080 x 45.95) + (0.073 x 46.95) + (0.738 x 47.95) + (0.055 x 48.95) + (0.054 x 49.94)
= 3.676 + 3.42735 + 35.3871 + 2.69225 + 2.69676
or 48
Standard atomic weight = 47.86
Ti 48
22 Ti 49
22 Ti 50
22
7.3% 5.5% 5.4%
46.95 48.95 49.94
+ (F3 x Ma3) + (F4 x Ma4) + (F5 x Ma5)
Review
Relative atomic mass = average atomic mass in
sample
Standard atomic weight = average atomic mass in a
normal sample
Copyright This video is made for educational purposes.
Questions Directly message us OR
Email [email protected].