Which chemical equation is correctly balanced?
(1) h2(g) + o2(g)=> h2o(g)
(2) n2(g) + h2(g) => nh3(g)
(3) 2nacl(s)=> na(s) + cl2(g)
(4) 2kcl(s) => 2k(s) + cl2(g)

(1) isn't balanced because there are two Hs and two Os on the left, and two Hs and one O on the right
(2) isn't balanced because there are two Ns and two Hs on the left, but one N and three Hs on the right
(3) isn't balanced because there are two Nas and two Cls on the left, but only one Na and two Cls on the right
(4) is balanced because there are two Ks and two Cls on theleft, and two Ks and two Cls on the right