Write the empirical formula of at least four binary ionic compounds that could be formed from the following ions Fe^2+, Ni^4+, Cl^-, S^2-

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

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?

How many moles of carbon dioxide will form if 2.5 moles of c3h8 is burned