A 250 mL solution of common salt and water was prepared so that the concentration of the solution in terms of mass of volume percentage would be 15%. Calculate the mass of common salt dissolved in water to prepare this solution.

Imagine that you have produced several versions of lactase, each of which differs from normal lactase by a single amino acid. describe a test that could indirectly determine which of the versions significantly alters the three-dimensional shape of the lactase protein.

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

How does the atmosphere to make earth livable? check all that apply. causes the seasons contains oxygen provides warmth creates important nutrients blocks harmful energy from the sun plz like !