seconds required (half life)

In the presence of excess thiocyanate ion, SCN-, the following reaction is first order in iron(III) ion, Fe3+; the rate constant is 1.27 s-1.

Fe3+(aq) + SCN-(aq) ? Fe(SCN)2+(aq)

If 90.0% reaction is required to obtain a noticeable color from the formation of the Fe(SCN)2+ ion, how many seconds are…