Nitrogen has atomically mass of about 14 amu and a atomic number of 7. how many neutrons does nitrogen have ?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.

What is the mass of naoh that would have to be added to 500 ml of a solution of 0.20 m acetic acid in order to achieve a ph of 5.0?