The helium used to fill birthday balloons doesn’t come out of the air, but from out of the ground. Some of the gas might escape from the ground into the

atmosphere, but the majority of it is trapped in Earth’s crust. Based on what you have learned in today’s lab, give a reasonable explanation for the presence of helium gas in Earth’s crust.

Electroplating is a way to coat a complex metal object with a very thin (and hence inexpensive) layer of a precious metal, such as silver or gold. in essence the metal object is made the cathode of an electrolytic cell in which the precious metal cations are dissolved in aqueous solution. suppose a current of 480.ma is passed through an electroplating cell with an aqueous solution of agno3 in the cathode compartment for 46.0 seconds. calculate the mass of pure silver deposited on a metal object made into the cathode of the cell. round your answer to 3 significant digits. also, be sure your answer contains a unit symbol. ×10μ

Friction removes energy from objects in motion. which statement best describes how this works? a) friction transforms ke into thermal energy b) friction transfers thermal energy to ke c) friction transforms te into pe d) friction transforms pe into ke e) friction transfers ke into pe

How many electrons does each element require in its valence shell to become stable?