Hydrogen and chlorine gases react to form HCl. A scientist sets up a reaction vessel in which the chlorine gas is contained at one end of a long tube and hydrogen gas is contained at the other end of the long tube. In order to get the HCl to form in exactly the center of the tube, he needs to release the slower moving gas first to give it more time to reach the center. Which gas should he release first?

Astudent pours 10.0 g of salt into a container of water and observes the amount of time it takes for the salt to dissolve. she then repeats the process using the same amounts of salt and water but this time she slowly stirs the mixture while it is dissolving. the student performs the experiment one more time but this time she stirs the mixture rapidly. the dependent variable in this experiment is: time for salt to dissolve speed of stirring amount of water mass of salt