1. Calculate the energy of one mole of photons ($E$): The energy of a photon is given by $E = \frac{hc}{\lambda}$. For one mole, we multiply by Avogadro's constant ($N_A$). $E = \frac{N_A hc}{\lambda}$ Given: $N_A = 6.022 \times 10^{23} \text{ mol}^{-1}$ $h = 6.626 \times 10^{-34} \text{ J s}$ $c = 3.0 \times 10^8 \text{ m s}^{-1}$ $\lambda = 300 \text{ nm} = 300 \times 10^{-9} \text{ m} = 3.0 \times 10^{-7} \text{ m}$

$E = \frac{(6.022 \times 10^{23} \text{ mol}^{-1})(6.626 \times 10^{-34} \text{ J s})(3.0 \times 10^8 \text{ m s}^{-1})}{3.0 \times 10^{-7} \text{ m}}$ $E = \frac{11.969 \times 10^{-3}}{3.0 \times 10^{-7}} \text{ J mol}^{-1} \approx 3.99 \times 10^5 \text{ J mol}^{-1}$

2. Apply the Photoelectric Equation: Energy of photon = Minimum energy to remove electron (Work Function) + Kinetic Energy $E = W_0 + K.E.$ $W_0 = E - K.E.$

3. Calculate the Work Function ($W_0$): Given $K.E. = 1.68 \times 10^5 \text{ J mol}^{-1}$ $W_0 = (3.99 \times 10^5 \text{ J mol}^{-1}) - (1.68 \times 10^5 \text{ J mol}^{-1})$ $W_0 = (3.99 - 1.68) \times 10^5 \text{ J mol}^{-1}$ $W_0 = 2.31 \times 10^5 \text{ J mol}^{-1}$