How do you calculate the number of g of solute that would be needed to make the following?

Question

2.50X10^2mL of 0.100M NaCl?

Answer 1

You want how many moles? That's M x L.
0.250 L x 0.100 M = 0.0250 moles
moles NaCl = grams NaCl/molar mass NaCl. solve for grams.