Two different proteins \(X\) and \(Y\) are dissolved in aqueous solution at \(37^{\circ} \mathrm{C}\) . The proteins bind in a \(1 : 1\) ratio to form \(X Y . A\) solution that is initially 1.00 \(\mathrm{mM}\) in each protein is allowed to reach equilibrium. At equilibrium, 0.20 \(\mathrm{mM}\) of free \(\mathrm{X}\) and 0.20 \(\mathrm{mM}\) of free Y remain. What is \(K_{c}\) for the reaction?

Short Answer

Expert verified
The equilibrium constant, \(K_c\), for the reaction \(X + Y \rightleftharpoons XY\) can be determined using the given initial and equilibrium concentrations of X and Y. From the ICE table, we find that the change in concentration (x) is 0.80 mM and the equilibrium concentration of XY is also 0.80 mM. Using the formula \(K_c = \frac{[XY]}{[X][Y]}\) and substituting the equilibrium concentrations, we find that \(K_c = \frac{0.80}{(0.20)(0.20)} = 20\). Therefore, the equilibrium constant for this reaction is 20.

Step by step solution

01

Write the balanced chemical equation

Firstly, we need to write the balanced chemical equation for the reaction. Since the proteins X and Y bind in a 1:1 ratio to form XY, we can write the chemical equation as: \(X + Y \rightleftharpoons XY\)
02

Set up the ICE table

To find the equilibrium constant (\(K_c\)), we need to know the equilibrium concentrations of all the species involved in the reaction. We are given the initial and equilibrium concentrations of X and Y. We can set up an Initial, Change, and Equilibrium (ICE) table to represent the changes in concentrations during the reaction. | | X | Y | XY | |--------|------|------|------| | Initial| 1.00 | 1.00 | 0 | | Change | -x | -x | +x | | Equilibrium | 0.20 | 0.20 | ? |
03

Determine the change in concentration

From the ICE table, we can determine the change in concentration (x) for each species using the given equilibrium concentrations of X and Y: \(x = 1.00 - 0.20 = 0.80\)
04

Find the equilibrium concentration of XY

Now that we have found the change in concentration (x), we can determine the equilibrium concentration of XY: Initial concentration of XY + Change in concentration = Equilibrium concentration of XY \(0 + 0.80 = 0.80\,\text{mM}\)
05

Calculate the equilibrium constant, \(K_c\)

The equilibrium constant, \(K_c\), can be calculated using the equilibrium concentrations of the species in the chemical equation: \(K_c = \frac{[XY]}{[X][Y]}\) Substitute the equilibrium concentrations: \(K_c = \frac{0.80}{(0.20)(0.20)}\) Calculate the value of \(K_c\): \(K_c = \frac{0.80}{0.04} = 20\) Thus, the equilibrium constant for the reaction is 20.

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