Pls help me do this pls

Which atom or ion is the largest? a. k b. k+ c. ca d. ca2+ e. li

Sodium sulfate dissolves as follows: na2so4(s) → 2na+(aq) + so42- (aq). how many moles of na2so4 are required to make 1.0 l of solution in which the na concentration is 0.10 m?

If 22.5 liters of oxygen reacted with excess of hydrogen, how many liters of water vapor could be produced?