Calculating Stock Solution Volume for NaHCO3 5g/L: M1V1=M2V2

[frank1]

Homework Statement

Whats the stock solution volume required to prepare 100ml of a NaHCO3 solution 5g/L using a stock solution of NaHCO3 30g/L.

Homework Equations

M1*V1 = M2*V2

M = Molarity = mols/L

The Attempt at a Solution

NaHCO3 = 84g/mol
5g NaHCO3 = 0.0595238095238095mol
30g NaHCO3 = 0.3571428571428571mol

M1*V1 = M2*V2 => 0.0595238095238095*0.1 = 0.3571428571428571*V2
V2 = 0.01666L = 16,7mL

But the answer is 3,33 mL

 

[Borek]

16.7 mL is the right answer.

Note: there is no need to convert everything to moles and molar concentrations. Answer doesn't depend on the identity of the substance. Final solution must contain 0.5 g (0.1L*5g/L), so you need to start with 0.5g/30g liters of the stock solution and dilute it to 100 mL.