How much salt do I add. Simple math?

Question

I have 55ul of a solution with a salt concetration of 50 mM. How much 1 M NaCl (100 mM may be easier) do I need to add before I get a concentration of 150 mM.

thanks

Answer 1

we  will do this dilution with the dilution equation using 1 M NaCl as 1000mM



C1V1   &  C2V2  = C3V3

(55 uL) (50mM)  & (X uL)(1000mM) = (55uL + X) (150 uL)

2750 & 1000X = 8250 & 150X

850X = 5500

X = 6.47 uL

though it comes out that you need  to add 6.47uL of 1 Molar NaCl,

your answer (2 sigfigs) : you add 6.5 uL of 1 Molar NaCl