ANSWER: 1.41 x [tex]10^{-4}[/tex] grams
EXPLANATION:
1. The formula for mass is m=nM therefore we need to find moles (n) because we don't have that yet.
[tex]n = CV[/tex]
n = ([tex]2.40[/tex] × [tex]10^{-5}[/tex]) x 0.12 (I converted 120.0 mL to L, which makes it 0.12)
n = 0.00000288 mol
2. Now we can find the mass.
m = n x M
m = 0.00000288 x 49.0072 (molar mass, M, of NaCN is 49.0072)
m = 0.00014114073 grams ≈ 1.41 x [tex]10^{-4}[/tex] grams
