An element has two isotopes. One isotope has a percent abundance of 75.0% and a mass number of 25 amu. The second isotope has a percent abundance of 25.0% and a mass number of 28 amu. What is the average atomic mass of the element?

Some liquids can be distilled, but only at temperatures that are so high that it is impractical, or so high the compound decomposes. explain why distillation such compounds at significantly less than atmospheric pressure (some degree of vacuum) would solve this problem.