A single molecule of haemoglobin, $\text{Hb}$, is able to combine with four molecules of oxygen, as shown by the equation below. $\text{Hb(aq)} + 4\text{O}_2(aq) \rightleftharpoons \text{Hb(O}_2)_4(aq)$ At equilibrium, when the concentration of $\text{O}_2$ is $7.6 \times 10^{-6}\,\text{mol dm}^{-3}$, the equilibrium concentrations of $\text{Hb}$ and $\text{Hb(O}_2)_4$ are the same. What is the value of $K_c$ for this equilibrium?
- A$3.0 \times 10^{20}$
- B$1.3 \times 10^{5}$
- C$7.6 \times 10^{-6}$
- D$3.3 \times 10^{-21}$