Ocr chemistry alevelWatch
But, if you want to use Ag+ to compare the rate of hydrolysis of different haloalkanes, then you can't use OH- as a brown sludge of Ag2O will form.
So, instead of using OH- as the nucleophile, we use water. Now water is a rubbish nucleophile compared to OH-, so we have to give it a little help - we add some alcohol at the start to act as the common solvent. We also add AgNO3(aq) - this supplies the Ag+ for the precipitation and the H2O which is the nucleophile.
i.e. your suggestion in your OP is incorrect.
For the record Hedwigeeeee is describing the use of Ag+ to detect halide ions in aqueous salts, but omitted the testing for SO42-, which needs to be done before testing for halide ions.