Smh my old account sjg046 got deleted so uhh yuh but here I am i guess almost died

Iknow the answer is a but i don't know why

Find the mass in grams of 1.37x1020 particles of h3po4

In 1901, thomas edison invented the nickel-iron battery. the following reaction takes place in the battery. fe(s) + 2 nio(oh)(s) + 2 h2o(l) fe(oh)2(s) + 2 ni(oh)2(aq) how many mole of fe(oh)2, is produced when 5.35 mol fe and 7.65 mol nio(oh) react?