I was doing some questions on equilbrium. I got stuck in this particular question.
Identify which of the following reactions are reversible.
$$ \begin{align} \ce{Fe + S &-> FeS }\label{rxn:1}\tag{1}\\ \ce{NaCl + AgNO3 &-> AgCl + NaNO3}\label{rxn:2}\tag{2}\\ \ce{H2SO4 + Ba(OH)2 &-> BaSO4 + 2 H2O}\label{rxn:3}\tag{3}\\ \ce{H2 +I2 &-> 2HI }\label{rxn:4}\tag{4}\ \end{align} $$
I know that \eqref{rxn:2} and \eqref{rxn:3} cannot be reversible because one of the products is precipitated. I could not reach a conclusion between \eqref{rxn:1} and \eqref{rxn:4} (although I know that \eqref{rxn:4} is reversible). Is there a way to determine without actual experiments whether a reaction is reversible or not?