Answer:
[tex]C_2=1.25 M[/tex]
Explanation:
Hello,
In this case, since the concentration in #1 is 3M, during a dilution process, the moles of the solute (NaCl) remains the same, just the concentration and volume change as shown below:
[tex]n_1=n_2\\\\C_1V_1=C_2V_2[/tex]
In such a way, as the final volume is 1200 microliters, the resulting concentration turns out:
[tex]C_2=\frac{C_1V_1}{V_2}=\frac{3M*500\mu L}{1200\mu L}\\ \\C_2=1.25 M[/tex]
Best regards.