Asingle atom of an element has 21 neutrons 20 electrons and 20 protons which element is it

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?

Aweight lifter raises a 1600 n barbell to a height of 2.0 meters. how much work was done? w = fd a) 30 joules b) 3000 joules c) 320 joules d) 3200 joules

It takes 155. kj/mol to break a fluorine-fluorine single bond. calculate the maximum wavelength of light for which a flouine-flouring single bond could be broken by absorbing a single photon