How many grams of CH3SH must be added to water to prepare 410mL of a solution that is 2.5 M CH3SH?
How many mols do you want? That's mols = M x L = ?
Then mols = grams/molar mass. You know molar mass and mols, solve for grams.
Then mols = grams/molar mass. You know molar mass and mols, solve for grams.