A solution is prepared by adding 0.023 moles of H 3 O^ -4 to 3.33L of water. What is the pH of this solution?

If anyone would be able to me out with these three questions it would be these are from the chem 2202 course.

How many moles of oxygen gas are produced from the decomposition of six moles of potassium

Which reason best explains why metals are malleable? a)because they have delocalized electrons b)because they have localized electrons c)because they have ionic bonds d)because they have rigid bonds