ameliaxbowen7
12.12.2019 •
Chemistry
The molar mass of table salt (naci) is 58.5 g/mol.
what mass of salt is equivalent to 3.00 moles naci?
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Ответ:
What is the atomic mass of hafnium if, out of every 100 atoms, 5 have a mass of 176, 19 have a mass of 177, 27 have mass of 178, 14 have a mass of 179, and 35 have a mass of a 180?
Chemistry Atomic Mass
Average atomic mass of Hafnium
=
178.55
amu
Explanation:
If there are two isotopes an element
Average atomic mass
=
mass
a
×
fract
a
+
mass
b
×
fract
b
In the given problem about Hafnium, 5 isotopes have been given.
Extending the above expression to 5 isotopes
We obtain
Average atomic mass
=
176
×
0.05
+
177
×
0.19
+
178
×
0.27
+
179
×
0.14
+
180
×
0.35
=
178.55
-.-.-.-.-.-.-.-.-.-.-.-.-.-
(Ensure that sum of all fractions adds to 1.
It is easy to find the fraction of each isotope in the question as total number is given as 100 atoms. Number of each isotope divided by 100)
Always use average atomic masses for mass calculations involving elements or compounds.