Hey there!:
Molar mass urea = 60 g/mol
Number of moles of solute:
moles solute = mass solute / molar mass
moles solute = 16 / 60
moles solute => 0.2666 moles of urea
Volume in liters:
42.3 mL / 1000 => 0.0423 L
Therefore:
Molarity = moles of solute / volume of solution
Molarity = 0.2666 / 0.0423
= 6.302 M
Hope that helps!
