How do you write the formation equation for (i) #CH_3COOH# and (ii) #NaHS#?
I assume you mean the formation reactions, i.e. the reactions that form the products from their elements in their standard states; that is, at
If you are unsure which phases to use, look in the Appendix of your textbook and find your element... if you see
Well, acetic acid consists of
#"C"(gr) + "H"_2(g) + "O"_2(g) -> "CH"_3"COOH"#
(Your book might denote carbon as
Balance to get:
#color(blue)(2"C"(gr) + 2"H"_2(g) + "O"_2(g) -> "CH"_3"COOH"(l))#
(I know that acetic acid in its standard state is a liquid, because that is how it is when it is in its pure form; its melting point is around
It should be easy to point to what elements are in sodium hydrosulfide:
The only tricky element here is sulfur, whose elemental state is "orthorhombic sulfur", which we denote as
The UNBALANCED reaction is therefore:
#"Na"(s) + "H"_2(g) + "S"_8(o rtho) -> "NaHS"(s)#
I'll leave it up to you to inspect this answer properly and balance this second reaction yourself. Note that it is entirely reasonable to have fractional stoichiometric coefficients for formation reactions.