How can I calculate pH given pOH of 4.5?

Which of the following is a testable hypothesis? a. if i brush my teeth, i will get fewer cavities than if i don't brush my teeth. b. green toothpaste tastes better than blue toothpaste or red toothpaste. c. smart, careful, healthy people always brush their teeth. d. it's wrong to not brush your teeth before you have an important conversation with someone.

How many grams of co(g) are there in 74.5 ml of the gas at 0.933 atm and 30o c?

How would the number of moles (n) of o2 change if the atmospheric pressure doubled but all other variables stayed the same