Explanation:
i suppose this is chemistry..
no of moles = mass / molar mass
you are given the mass, 4.0g, you need to find the molar mass ( Mr ) of NaCl.
Mr = 23 + 35.5
Mr = 58.5
now that you know the Mr of Nacl, just use the formula:
n = m/mr
n= 4/ 58.5
n= 0.068376..
no of moles = 0.068 moles.
