Question:
Consider the equilibrium reactions:
\(H_3PO_4 \rightleftharpoons H^+ + H_2PO_4^-\) \((K_1)\)
\(H_2PO_4^- \rightleftharpoons H^+ + HPO_4^{2-}\) \((K_2)\)
\(HPO_4^{2-} \rightleftharpoons H^+ + PO_4^{3-}\) \((K_3)\)
The equilibrium constant, \(K_c\), for the following dissociation:
\(H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-}\)
is:
Consider the equilibrium reactions:
\(H_3PO_4 \rightleftharpoons H^+ + H_2PO_4^-\) \((K_1)\)
\(H_2PO_4^- \rightleftharpoons H^+ + HPO_4^{2-}\) \((K_2)\)
\(HPO_4^{2-} \rightleftharpoons H^+ + PO_4^{3-}\) \((K_3)\)
The equilibrium constant, \(K_c\), for the following dissociation:
\(H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-}\)
is:
\(H_3PO_4 \rightleftharpoons H^+ + H_2PO_4^-\) \((K_1)\)
\(H_2PO_4^- \rightleftharpoons H^+ + HPO_4^{2-}\) \((K_2)\)
\(HPO_4^{2-} \rightleftharpoons H^+ + PO_4^{3-}\) \((K_3)\)
The equilibrium constant, \(K_c\), for the following dissociation:
\(H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-}\)
is:
Show Hint
Remember the three fundamental rules for manipulating equilibrium constants:
1. If you add reactions, multiply their $K$ values.
2. If you reverse a reaction, take the reciprocal ($1/K$).
3. If you multiply a reaction by a factor $n$, raise $K$ to the power $n$ ($K^n$).
Updated On: Jun 3, 2026
- \(K_1 + K_2 + K_3\)
- \(K_1 K_2 K_3\)
- \(\dfrac{K_1}{K_2 K_3}\)
- \(\dfrac{K_1 K_2}{K_3}\)
Show Solution
Verified By Collegedunia
The Correct Option is B
Solution and Explanation
Concept:
When a chemical reaction can be expressed as the sum of two or more individual reactions, the equilibrium constant for the net reaction is the product of the equilibrium constants of the individual steps.
Step 1: Identify the relationship between the reactions.
The three stepwise dissociation reactions of phosphoric acid are:
• \(H_3PO_4 \rightleftharpoons H^+ + H_2PO_4^-\) (Equilibrium constant = \(K_1\))
• \(H_2PO_4^- \rightleftharpoons H^+ + HPO_4^{2-}\) (Equilibrium constant = \(K_2\))
• \(HPO_4^{2-} \rightleftharpoons H^+ + PO_4^{3-}\) (Equilibrium constant = \(K_3\))
Step 2: Add the reactions together.
Summing the three equations:
\[ H_3PO_4 + H_2PO_4^- + HPO_4^{2-} \rightleftharpoons (H^+ + H_2PO_4^-) + (H^+ + HPO_4^{2-}) + (H^+ + PO_4^{3-}) \] \[ H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-} \] Intermediate species \(H_2PO_4^-\) and \(HPO_4^{2-}\) cancel out from both sides.
Step 3: Calculate the net equilibrium constant \((K_c)\).
\[ K_c = K_1 \times K_2 \times K_3 \]
Step 1: Identify the relationship between the reactions.
The three stepwise dissociation reactions of phosphoric acid are:
• \(H_3PO_4 \rightleftharpoons H^+ + H_2PO_4^-\) (Equilibrium constant = \(K_1\))
• \(H_2PO_4^- \rightleftharpoons H^+ + HPO_4^{2-}\) (Equilibrium constant = \(K_2\))
• \(HPO_4^{2-} \rightleftharpoons H^+ + PO_4^{3-}\) (Equilibrium constant = \(K_3\))
Step 2: Add the reactions together.
Summing the three equations:
\[ H_3PO_4 + H_2PO_4^- + HPO_4^{2-} \rightleftharpoons (H^+ + H_2PO_4^-) + (H^+ + HPO_4^{2-}) + (H^+ + PO_4^{3-}) \] \[ H_3PO_4 \rightleftharpoons 3H^+ + PO_4^{3-} \] Intermediate species \(H_2PO_4^-\) and \(HPO_4^{2-}\) cancel out from both sides.
Step 3: Calculate the net equilibrium constant \((K_c)\).
\[ K_c = K_1 \times K_2 \times K_3 \]
Was this answer helpful?
0
0
Top AP EAPCET Chemistry Questions
- The four quantum numbers of the valence electron of potassium are :
- The volume of $0.02\, M$ acidified permanganate solution required for complete reaction of $60\, mL$ of $0.01\, MI^{-}$ ion solution to form $I_2$ in $mL$ is
- In which of the following the election gain enthalpy of elements is correctly arranged?
- The radii of $ \text{F,}{{\text{F}}^{-}}\text{O} $ and $ {{\text{O}}^{2-}} $ are in the order
- Which of the following has the highest first ionization potential?
View More Questions
Top AP EAPCET Chemical equilibria Questions
- Observe the following equilibrium at T(K) \[ H_2(g) + I_2(g) \rightleftharpoons 2HI(g) \] Which one of the following does not disturb the above equilibrium?
- Which one of the pairs will form a buffer solution?
- For the reaction $\text{N}_2\text{(g)} + 3\text{H}_2\text{(g)} \rightleftharpoons 2\text{NH}_3\text{(g)}$, the relation between $K_p$ and $K_c$ is
- The conjugate base of $\text{H}_{2}\text{PO}_{4}^{-}$ is
- For the reaction $2HI(g)\rightleftharpoons H_{2}(g)+I_{2}(g)$, the correct expression relating the degree of dissociation ($\alpha$) of HI and equilibrium constant $K_{p}$ is
View More Questions
Top AP EAPCET Questions
- A body is projected from the ground at an angle of $\tan^{-1} \left( \frac{8}{7}\right)$ with the horizontal. The ratio of the maximum height attained by it to its range is
- The four quantum numbers of the valence electron of potassium are :
- A lens forms real and virtual images of an object, when the object is at $u_{1}$ and $u_{2}$ distances respectively. If the size of the virtual image is double that of the real image, then the focal length of the lens is (take, the magnification of the real image as $m$ )
- Two spheres $P$ and $Q$, each of mass $200\, g$ are attached to a string of length one metre as shown in the figure. The string and the spheres are then whirled in a horizontal circle about $O$ at a constant angular speed. The ratio of the tension in the string between $P$ and $Q$ to that of between $P$ and $O$ is $(P$ is at mid-point of the line joining $O$ and $Q$ )
- The volume of $0.02\, M$ acidified permanganate solution required for complete reaction of $60\, mL$ of $0.01\, MI^{-}$ ion solution to form $I_2$ in $mL$ is
View More Questions