Acertain element exists as two different isotopes. 92.4% of its atoms have a mass of 7.016 amu and 7.60% of its atoms have a mass of 6.015 amu. what is the average atomic mass of this element?

a
6.52 amu
b
6.09 amu
c
6.94 amu
d
694 amu
answer asap

6.94 amu

Explanation:

The average atomic mass of an element can be calculated from the addition mass of their isotopes.

For the exercise you should follow these steps:

1) Change the percentages to fraction, just need to divide by 100.

To avoid confusions and to keep all the information organize, you can make a table like this:

Abundance  

%        fraction (divide by 100)

92.40.924

7.600.076

total100.01.000    

                           ***You can move the decimal point two places to the left.

As you can see in the table, when you add percentages the result is equal to 100, but when you sum fractions the result is equal to 1.

Now multiply the mass with their respective fraction:

0.924 (7.016 amu) = 6.483 amu

0.076 (6.015 amu) = 0.457 amu

The final table will be:

%     fraction    mass amu  mass amu  

92.40.9247.016          6.483

7.600.0766.015          0.457

total100.01.000         Average 6.940

The average atomis mass of this element is 6.94 amu

You can make this type of tables and do the calculations in excel, check the table that I attached.