How many valence electrons does iron have?

In this chemical reaction, 325 grams of barium (ba) react completely. how many moles of lithium (li) are produced?

Ineed to find the answer of this question because i dont understand it

When a chemist collects hydrogen gas over water, she ends up with a mixture of hydrogen and water vapor in her collecting bottle. if the pressure in the collecting bottle is 97.1 kilopascals and the vapor pressure of the water is 3.2 kilopascals, what is the partial pressure of the hydrogen?