A fictitious element X is composed of 25.0 percent of the isotope "x, 30.0 percent of the isotope *x, and 45.0 percent of the isotope **x. Estimate the atomic mass of element X.

When a chemist collects hydrogen gas over water, she ends up with a mixture of hydrogen and water vapor in her collecting bottle. if the pressure in the collecting bottle is 97.1 kilopascals and the vapor pressure of the water is 3.2 kilopascals, what is the partial pressure of the hydrogen?