Answer
The molarity of the solution is equal to $0.0684$ $M$.
Work Step by Step
$100$ mL = $100 \times 10^{-3}$ L = 0.100 L
$400$ mg = $400 \times 10^{-3}$ g = 0.400 g
1. Calculate the molar mass $(NaCl)$:
22.99* 1 + 35.45* 1 = 58.44g/mol
2. Calculate the number of moles $(NaCl)$
$n(moles) = \frac{mass(g)}{mm(g/mol)}$
$n(moles) = \frac{ 0.400}{ 58.44}$
$n(moles) = 6.84\times 10^{- 3}$
3. Find the concentration in mol/L $(NaCl)$:
$C(mol/L) = \frac{n(moles)}{volume(L)}$
$ C(mol/L) = \frac{ 6.84\times 10^{- 3}}{ 0.100} $
$C(mol/L) = 0.0684$ $M$
