Hey there!:
Molar mass NaCl = 58.44 g/mol
Number of moles = mass of solute / molar mas
Number of moles = 0.900 / 58.44
Number of moles = 0.0154 moles of NaCl
Volume in liters of solution :
100.0 mL / 1000 => 0.1 L
Therefore:
Molarity = number of moles / volume in liters
Molarity = 0.0154 / 0.1
Molarity = 0.154 M
Hope this helps!
