Answer: 58.44
concentration of NaCl = 2M
Volume = 500ml = 0.5L
No of mole of NaCl = conc. *volume
No of mole of NaCl = 0.5*2 = 1mol
Molar mass of NaCl = 58.44g/mol
Mass of NaCl = Molar mass * no of mole
Mass of NaCl = 1*58.44 = 58.44g
58.44g of NaCl was added