Question

Can anyone help ASAP!!

Answer 1

The formula to determine the average atomic mass is:

Average atomic mass =
`mass of the isotope 1 * natural abundance of isotope 1` +
`mass of the isotope 2 * natural abundance of isotope 2` + ........
`+ mass of the isotope n * natural abundance of isotope n` -(1)

The atomic mass of first isotope of magnesium = 24 u (given)

The natural abundance of first isotope = 78.70 % (given)

The atomic mass of second isotope of magnesium = 25 u (given)

The natural abundance of first isotope = 10.13 % (given)

The atomic mass of third isotope of magnesium = 26 u (given)

The natural abundance of first isotope = 11.17 % (given)

Substituting the values in formula (1):

atomic weight =
`(24 * 0.7870) + (25 * 0.1013) + (26 * 0.1117)`

atomic weight =
`24.4625 u`

Hence, the atomic weight of naturally occurring isotopic mixture is
`24.4625 u`.