A mixture of gases at a total pressure of 725 mmHg contains nitrogen, carbon dioxide, helium, and oxygen. The partial pressure of carbon dioxide is 175 mmHg, the partial pressure of nitrogen is 355 mmHg, and the partial pressure of helium is 15 mmHg. What is the partial pressure of oxygen?

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