If an atom has 7 protons, 8 neutrons and 9 electrons, what is the mass number?

Astudent carefully transfers 30 g of water and 30 g of alcohol in a glass tube, forming two layers and filling the tube completely. after sealing the tube, the student mixes the solutions, and notices a bubble that forms in the tube. what is the mass of the contents in the glass tube after mixing?

What is the area in square meters of 448 g ai foil that has a thickness of 23921 nm? the density is 2.70 g/cm

What kind of intermolecular forces act between a hydrogen fluoride molecule and a hydrogen peroxide molecule? note: if there is more than one type of intermolecular force that acts, be sure to list them all, with a comma between the name of each force.