CAPE Chemistry Unit 2 · 2013 · Paper 1 · Question Q21

The complex ion [\text{FeSCN}]^{2+} has a molar absorptivity (\varepsilon) of 7.0 \times 10^3\text{ dm}^3\text{ mol}^{-1}\text{ cm}^{-1}. The concentration of its solution, which gives an absorbance of 4.2 when measured in a 2-cm cell, is

1. (A)3 \times 10^{-3}\text{ mol dm}^{-3}
2. (B)6 \times 10^{-3}\text{ mol dm}^{-3}
3. (C)3 \times 10^{-4}\text{ mol dm}^{-3}
4. (D)6 \times 10^{-4}\text{ mol dm}^{-3}