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?

You are attempting to recrystallize a crude product mixture. you add the appropriate amount of hot solvent and are allowing the solution to slowly cool to room temperature. however, at room temperature no crystals have appeared, which of the following methods should be used to induce crystallization? choose all correct answers. a) place the flask in an ice bath. b) swirl the contents of the flask. c) add a small seed crystal of the desired product. d) scratch the inside of the glassware using a stir rod. it can be multiple choices