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Answer:
24.309
Explanation:
mass×percentage+.. = average amu
23.985×78.7/100+24.986×10.13/100+25.983×11.17/100
to three decimal places
=24.309
Using dimensional analysis, we can find the moles of strontium by comparing the mass of strontium to it's atomic mass.
You can find the atomic mass of Sr on the periodic table:
Atomic Mass Sr = 87.62g/mol
In case you are not familiar, dimensional analysis works like this:
(what we know) x (conversion factor) = what we are looking for
The conversion factor compares the units of what we know to the units of what we are looking for. In this case, the conversion factor is:
1 mol/87.62g
The important thing to note about the conversion factor is that you want to be able to cancel out the units of your given measurement (in this case, it is the mass)
So, our full solution will be:
moles Sr = (175.24 g)x(1 mol/87.62 g)
(cancel out the mass units)
moles Sr = 175.24 x 1 mol/87.62
= 2.00 mol Sr
Hope this helped you!
Answer : The correct answer is, (c) the number of neutrons
Explanation :
Isotope : It is defined as the element that have the same number of protons but have the different number of neutrons of each of the atom.
Atomic number is defined as the number of protons or number of electrons.
Atomic number = number of protons = number of electrons
Mass number is defined as the sum of number of protons and number of neutrons.
Number of neutrons = Mass number - Atomic number
For example : For Carbon - 13 isotope.
Mass number = 13
Atomic number = 6
Number of neutrons = Mass number - Atomic number
Number of neutrons = 13 - 6 = 7
Hence, the difference between the mass number of an isotope and its atomic number is the number of neutrons.
