There are two important isotopes of uranium— and ; these isotopes are nearly identical chemically but have different atomic masses. Only is very useful in nuclear reactors. One of the techniques for separating them (gas diffusion) is based on the different average velocities of uranium hexafluoride gas, . (a) The molecular masses for and are 349.0 g/mol and 352.0 g/mol, respectively. What is the ratio of their average velocities?

Malik formed a hypothesis that an increase in atmospheric oxygen levels by 10% would cause red-legged grasshoppers to grow larger than normal. suppose that malik performs an experiment to test his hypothesis. which of these actions would represent a scientific mistake in his experiment? a. he experiments on live grasshoppers instead of preserved ones. b. he focuses on red-legged grasshoppers instead of all kinds of grasshoppers. c. he varies the nitrogen and carbon dioxide levels in the air from one trial to the next. d. he conducts the experiment in a controlled lab setting with a lab partner. e. he measures the mass and length of his specimens at the start of each trial.