Describe what dynamic equilibrium means.
Reaction 4 shows the reversible reaction between yellow $\text{Fe}^{3+}\text{(aq)}$ and colourless $\text{SCN}^{-}\text{(aq)}$ to form red $\text{FeSCN}^{2+}\text{(aq)}$: reaction 4: $\text{Fe}^{3+}\text{(aq)} + \text{SCN}^{-}\text{(aq)} \rightleftharpoons \text{FeSCN}^{2+}\text{(aq)}$ An equilibrium mixture contains $\text{Fe}^{3+}\text{(aq)}$, $\text{SCN}^{-}\text{(aq)}$ and $\text{FeSCN}^{2+}\text{(aq)}$. A few colourless crystals of soluble $\text{KSCN(s)}$ are added. The mixture is then left until equilibrium is re-established. The temperature of the two equilibrium mixtures is identical. Deduce the changes that occur, if any, in the equilibrium mixture after $\text{KSCN(s)}$ is added compared with the original equilibrium mixture: • change in appearance • change in relative concentration of $\text{Fe}^{3+}\text{(aq)}$ • change in value of the equilibrium constant, $K_c$.
The equilibrium constant expression for reaction 4 is given below: $K_c = \frac{[\text{FeSCN}^{2+}\text{(aq)}]}{[\text{Fe}^{3+}\text{(aq)}] \times [\text{SCN}^{-}\text{(aq)}]}$ $5.00 \times 10^{-5}\ \text{mol}$ of $\text{Fe}^{3+}\text{(aq)}$ and $5.00 \times 10^{-5}\ \text{mol}$ of $\text{SCN}^{-}\text{(aq)}$ are mixed and allowed to reach equilibrium. The total volume of the mixture is $25.0\ \text{cm}^3$. At equilibrium, the concentration of $\text{FeSCN}^{2+}\text{(aq)}$ is $4.23 \times 10^{-4}\ \text{mol dm}^{-3}$. Calculate the equilibrium constant, $K_c$, for reaction 4. Include the units in your answer.
Calculate the equilibrium constant, $K_c$, for reaction 4. Include units in your answer.
Determine the complete electronic configuration of $\text{Fe}^{3+}$.
$\text{SCN}^-(aq)$ is colourless. Finish the dot-and-cross diagram in Fig. 3.1 to show how the outer electrons are arranged in an $\text{SCN}^-$ ion.