There are two isotopes of an unknown element, X-19 and X-21. The abundance of X-19 is 12.01%. Now that you have the contribution from the X-19 isotope (2.282) and from the X-21 isotope (18.48), what is the average atomic mass (in amu) of this element using four significant figures

The average atomic mass of X is 16.53

Explanation:

Mass of isotope X-19  = 2.282  

% abundance of isotope X-19 = 12.01% =

Mass of isotope X-21 = 18.48

% abundance of isotope X-21 = (100-12.01)% =

Formula used for average atomic mass of an element :

Therefore, the average atomic mass of X is 16.53

93.2 ml + 3920 ml = 4013 ml total  

(93.2 ml) * (2.03 m) / (4013 ml) = 0.0471 m

the volume in in l of the diluted solution would be 0.0471 m.