How many grams of NaCl with a molar mass of 58.44 would be needed to make 2.5 L of 0.00500 solution?
Use the definition of molarity.
M = # mols/Liter of solution. You know M (I guess you left off the M for 0.00500???) and you know liters. Calculate # mols. Then use #mols = grams/molar mass. You know # mols and you know molar mass. Calculate grams.