What is the % oxygen by mass in K2SO4?

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?

How many moles of carbon dioxide will form if 2.5 moles of c3h8 is burned

Aradio signal from a gps satellite take only about 0.067 seconds to reach a gps reciever. if the speed of light is about 300,000km/s, then approximately how far away is the reciever from from the satellite?