Question

What is the concentration, in millimolar, of a 1 mg/ml solution of NaCl (molecular weight = 58 Da)?

Answer 1

Step-by-step explanation:

Relation between molarity and molar mass is as follows.

Molarity =
`\frac{mass}{\text{molar mass}} * (1000)/(V (in ml))`

It is given that mass is 1 mg/ml which is also equal to
`10^(-3)` g.

Molecular mass = 58 Da = 58 g/mol

Volume = 1 ml

Therefore, calculate molarity as follows.

Molarity =
`\frac{mass}{\text{molar mass}} * (1000)/(V (in ml))`

=
`(10^(-3)g)/(58 g/mol) * (1000)/(1 ml)`

= 0.0172 molar

It is known that 1 molar equals 1000 millimolar.

So, 0.0172 molar =
`0.0172 molar * (1000 millimolar)/(1 molar)`

= 17.2 millimolar

Thus, we can conclude that the concentration of given solution is 17.2 millimolar.