# 17.1: Common-Ion Effect in Acid-Base Equilibria (2023)

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##### Learning Objectives
• Recognize common ions from various salts, acids, and bases.
• Calculate concentrations involving common ions.
• Calculate ion concentrations involving chemical equilibrium.

The common-ion effect is used to describe the effect on an equilibrium involving a substance that adds an ion that is a part of the equilibrium.

## Introduction

The solubility products Ksp's are equilibrium constants in heterogeneous equilibria (i.e., between two different phases). If several salts are present in a system, they all ionize in the solution. If the salts contain a common cation or anion, these salts contribute to the concentration of the common ion. Contributions from all salts must be included in the calculation of concentration of the common ion. For example, a solution containing sodium chloride and potassium chloride will have the following relationship:

$\mathrm{[Na^+] + [K^+] = [Cl^-]} \label{1}$

Consideration of charge balance or mass balance or both leads to the same conclusion.

## Common Ions

When $$\ce{NaCl}$$ and $$\ce{KCl}$$ are dissolved in the same solution, the $$\mathrm{ {\color{Green} Cl^-}}$$ ions are common to both salts. In a system containing $$\ce{NaCl}$$ and $$\ce{KCl}$$, the $$\mathrm{ {\color{Green} Cl^-}}$$ ions are common ions.

$\mathrm{NaCl \rightleftharpoons Na^+ + {\color{Green} Cl^-}} \nonumber$

$\mathrm{KCl \rightleftharpoons K^+ + {\color{Green} Cl^-}} \nonumber$

$\mathrm{CaCl_2 \rightleftharpoons Ca^{2+} + {\color{Green} 2 Cl^-}} \nonumber$

$\mathrm{AlCl_3 \rightleftharpoons Al^{3+} + {\color{Green} 3 Cl^-}} \nonumber$

$\mathrm{AgCl \rightleftharpoons Ag^+ + {\color{Green} Cl^-}} \nonumber$

For example, when $$\ce{AgCl}$$ is dissolved into a solution already containing $$\ce{NaCl}$$ (actually $$\ce{Na+}$$ and $$\ce{Cl-}$$ ions), the $$\ce{Cl-}$$ ions come from the ionization of both $$\ce{AgCl}$$ and $$\ce{NaCl}$$. Thus, $$\ce{[Cl- ]}$$ differs from $$\ce{[Ag+]}$$. The following examples show how the concentration of the common ion is calculated.

##### Example $$\PageIndex{1}$$

What are $$\ce{[Na+]}$$, $$\ce{[Cl- ]}$$, $$\ce{[Ca^2+]}$$, and $$\ce{[H+]}$$ in a solution containing 0.10 M each of $$\ce{NaCl}$$, $$\ce{CaCl2}$$, and $$\ce{HCl}$$?

###### Solution

Due to the conservation of ions, we have

$\mathrm{[Na^+] = [Ca^{2+}] = [H^+] = 0.10\: \ce M} \nonumber$

but

\begin{alignat}{3} \nonumber &\ce{[Cl- ]} &&= && && \:\textrm{0.10 (due to NaCl)}\\ \nonumber & && && + &&\mathrm{\:0.20\: (due\: to\: CaCl_2)}\\ \nonumber & && && + &&\mathrm{\:0.10\: (due\: to\: HCl)}\\ \nonumber & &&= && &&\mathrm{\:0.40\: M} \nonumber \end{alignat}

(Video) 17.1 Acid base equiilibria- Common ion effect
##### Exercise $$\PageIndex{1}$$

John poured 10.0 mL of 0.10 M $$\ce{NaCl}$$, 10.0 mL of 0.10 M $$\ce{KOH}$$, and 5.0 mL of 0.20 M $$\ce{HCl}$$ solutions together and then he made the total volume to be 100.0 mL. What is $$\ce{[Cl- ]}$$ in the final solution?

###### Solution

$\mathrm{[Cl^-] = \dfrac{0.1\: M\times 10\: mL+0.2\: M\times 5.0\: mL}{100.0\: mL} = 0.020\: M} \nonumber$

Le Châtelier's Principle states that if an equilibrium becomes unbalanced, the reaction will shift to restore the balance. If a common ion is added to a weak acid or weak base equilibrium, then the equilibrium will shift towards the reactants, in this case the weak acid or base.

##### Example $$\PageIndex{2}$$: Solubility of Lead Chloride

Consider the lead(II) ion concentration in this saturated solution of PbCl2. The balanced reaction is

$PbCl_{2 (s)} \rightleftharpoons Pb^{2+} _{(aq)} + 2Cl^-_{(aq)} \nonumber$

Defining $$s$$ as the concentration of dissolved lead(II) chloride, then:

$[Pb^{2+}] = s \nonumber$

$[Cl^- ] = 2s \nonumber$

These values can be substituted into the solubility product expression, which can be solved for $$s$$:

$\begin{eqnarray} K_{sp} &=& [Pb^{2+}] [Cl^-]^2 \\ &=& s \times (2s)^2 \\ 1.7 \times 10^{-5} &=& 4s^3 \\ s^3 &=& \frac{1.7 \times 10^{-5}}{4} \\ &=& 4.25 \times 10^{-6} \\ s &=& \sqrt[3]{4.25 \times 10^{-6}} \\ &=& 1.62 \times 10^{-2}\ mol\ dm^{-3} \end{eqnarray} \nonumber$​The concentration of lead(II) ions in the solution is 1.62 x 10-2 M. Consider what happens if sodium chloride is added to this saturated solution. Sodium chloride shares an ion with lead(II) chloride. The chloride ion is common to both of them; this is the origin of the term "common ion effect".

Look at the original equilibrium expression again:

$PbCl_2 \; (s) \rightleftharpoons Pb^{2+} \; (aq) + 2Cl^- \; (aq) \nonumber$

What happens to that equilibrium if extra chloride ions are added? According to Le Châtelier, the position of equilibrium will shift to counter the change, in this case, by removing the chloride ions by making extra solid lead(II) chloride.

(Video) Acid - Base Equilibria | Common Ion Effect & Percent Dissociation.

Of course, the concentration of lead(II) ions in the solution is so small that only a tiny proportion of the extra chloride ions can be converted into solid lead(II) chloride. The lead(II) chloride becomes even less soluble, and the concentration of lead(II) ions in the solution decreases. This type of response occurs with any sparingly soluble substance: it is less soluble in a solution which contains any ion which it has in common. This is the common ion effect.

##### Example $$\PageIndex{3}$$

If an attempt is made to dissolve some lead(II) chloride in some 0.100 M sodium chloride solution instead of in water, what is the equilibrium concentration of the lead(II) ions this time? As before, define s to be the concentration of the lead(II) ions.

$[Pb^{2+}] = s \label{2}$

The calculations are different from before. This time the concentration of the chloride ions is governed by the concentration of the sodium chloride solution. The number of ions coming from the lead(II) chloride is going to be tiny compared with the 0.100 M coming from the sodium chloride solution.

In calculations like this, it can be assumed that the concentration of the common ion is entirely due to the other solution. This simplifies the calculation.

So we assume:

$[Cl^- ] = 0.100\; M \label{3}$

The rest of the mathematics looks like this:

$$\begin{split} K_{sp}& = [Pb^{2+}][Cl^-]^2 \\ & = s \times (0.100)^2 \\ 1.7 \times 10^{-5} & = s \times 0.00100 \end{split} \nonumber$$

therefore:

$$\begin{split} s & = \dfrac{1.7 \times 10^{-5}}{0.0100} \\ & = 1.7 \times 10^{-3} \, \text{M} \end{split} \label{4}$$

Finally, compare that value with the simple saturated solution:

Original solution:

$[Pb^{2+}] = 0.0162 \, M \label{5}$

Solution in 0.100 M NaCl solution:

$[Pb^{2+}] = 0.0017 \, M \label{6}$

The concentration of the lead(II) ions has decreased by a factor of about 10. If more concentrated solutions of sodium chloride are used, the solubility decreases further.

A Video Discussing Finding the Solubility of a Salt: Finding the Solubility of a Salt(opens in new window) [youtu.be]

(Video) The Common Ion Effect

## Common Ion Effect with Weak Acids and Bases

Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion. The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium.

Adding a common ion to a system at equilibrium affects the equilibrium composition, but not the ionization constant.

The common ion effect of H3O+ on the ionization of acetic acid

The common ion effect suppresses the ionization of a weak base by adding more of an ion that is a product of this equilibrium. Now consider the common ion effect of $$\ce{OH^{-}}$$ on the ionization of ammonia

Adding the common ion of hydroxide shifts the reaction towards the left to decrease the stress (in accordance with Le Chatelier's Principle), forming more reactants. This decreases the reaction quotient, because the reaction is being pushed towards the left to reach equilibrium. The equilibrium constant, $$K_b=1.8 \times 10^{-5}$$, does not change. The reaction is put out of balance, or equilibrium.

$Q_a = \frac{\ce{[NH_4^{+}][OH^{-}]}}{\ce{[NH3]}} \nonumber$

At first, when more hydroxide is added, the quotient is greater than the equilibrium constant. The reaction then shifts right, causing the denominator to increase, decreasing the reaction quotient and pulling towards equilibrium and causing Q to decrease towards K.

## Common Ion Effect on Solubility

When a slightly soluble ionic compound is added to water, some of it dissolves to form a solution, establishing an equilibrium between the pure solid and a solution of its ions. For the dissolution of calcium phosphate, one of the two main components of kidney stones, the equilibrium can be written as follows, with the solid salt on the left:

$\ce{Ca3(PO4)2(s) <=> 3Ca^{2+}(aq) + 2PO^{3−}4(aq)} \label{17.4.1}$

As you will discover in more advanced chemistry courses, basic anions, such as S2−, PO43, and CO32, react with water to produce OH and the corresponding protonated anion. Consequently, their calculated molarities, assuming no protonation in aqueous solution, are only approximate. The equilibrium constant for the dissolution of a sparingly soluble salt is the solubility product (Ksp) of the salt. Because the concentration of a pure solid such as Ca3(PO4)2 is a constant, it does not appear explicitly in the equilibrium constant expression. The equilibrium constant expression for the dissolution of calcium phosphate is therefore

$K=\dfrac{[\mathrm{Ca^{2+}}]^3[\mathrm{PO_4^{3-}}]^2}{[\mathrm{Ca_3(PO_4)_2}]} \label{17.4.2a}$

$[\mathrm{Ca_3(PO_4)_2}]K=K_{\textrm{sp}}=[\mathrm{Ca^{2+}}]^3[\mathrm{PO_4^{3-}}]^2 \label{17.4.2b}$

At 25°C and pH 7.00, $$K_{sp}$$ for calcium phosphate is 2.07 × 10−33, indicating that the concentrations of Ca2+ and PO43 ions in solution that are in equilibrium with solid calcium phosphate are very low. The values of Ksp for some common salts vary dramatically for different compounds (Table E3). Although $$K_{sp}$$ is not a function of pH in Equation $$\ref{17.4.2a}$$, changes in pH can affect the solubility of a compound.

The solubility product expression tells us that the equilibrium concentrations of the cation and the anion are inversely related. That is, as the concentration of the anion increases, the maximum concentration of the cation needed for precipitation to occur decreases—and vice versa—so that $$K_{sp}$$ is constant. Consequently, the solubility of an ionic compound depends on the concentrations of other salts that contain the same ions. This dependency is another example of the common ion effect where adding a common cation or anion shifts a solubility equilibrium in the direction predicted by Le Chatelier’s principle. As a result, the solubility of any sparingly soluble salt is almost always decreased by the presence of a soluble salt that contains a common ion.

Consider, for example, the effect of adding a soluble salt, such as CaCl2, to a saturated solution of calcium phosphate [Ca3(PO4)2]. We have seen that the solubility of Ca3(PO4)2 in water at 25°C is 1.14 × 10−7 M (Ksp = 2.07 × 10−33). Thus a saturated solution of Ca3(PO4)2 in water contains

• $$3 \times (1.14 \times 10^{−7}\; M) = 3.42 \times 10^{−7} M \; of \; Ca^{2+}$$
• $$2 \times (1.14 \times 10^{−7} M) = 2.28 \times 10^{−7} M \; of \; PO_4^{3−}$$

according to the stoichiometry shown in Equation $$\ref{17.4.2a}$$ (neglecting hydrolysis to form HPO42). If CaCl2 is added to a saturated solution of Ca3(PO4)2, the Ca2+ ion concentration will increase such that [Ca2+] > 3.42 × 10−7 M, making Q > Ksp. The only way the system can return to equilibrium is for the reaction in Equation $$\ref{17.4.2a}$$ to proceed to the left, resulting in precipitation of Ca3(PO4)2. This will decrease the concentration of both Ca2+ and PO43 until Q = Ksp.

##### Note

Adding a common ion decreases solubility, as the reaction shifts toward the left to relieve the stress of the excess product. Adding a common ion to a dissociation reaction causes the equilibrium to shift left, toward the reactants, causing precipitation.

##### Example $$\PageIndex{5}$$

Consider the reaction:

$PbCl_2(s) \rightleftharpoons Pb^{2+}(aq) + 2Cl^-(aq) \nonumber$

What happens to the solubility of PbCl2(s) when 0.1 M NaCl is added?

###### Solution

$K_{sp}=1.7 \times 10^{-5} \nonumber$

$Q_{sp}= 1.8 \times 10^{-5}\nonumber$

Identify the common ion: Cl​-

Notice: Qsp > Ksp The addition of NaCl has caused the reaction to shift out of equilibrium because there are more dissociated ions. Typically, solving for the molarities requires the assumption that the solubility of PbCl2 is equivalent to the concentration of Pb2+ produced because they are in a 1:1 ratio.

Because Ksp for the reaction is 1.7×10-5, the overall reaction would be (s)(2s)2= 1.7×10-5. Solving the equation for s gives s= 1.62×10-2 M. The coefficient on Cl- is 2, so it is assumed that twice as much Cl- is produced as Pb2+, hence the '2s.' The solubility equilibrium constant can be used to solve for the molarities of the ions at equilibrium.

The molarity of Cl- added would be 0.1 M because Na+ and Cl- are in a 1:1 ration in the ionic salt, NaCl. Therefore, the overall molarity of Cl- would be 2s + 0.1, with 2s referring to the contribution of the chloride ion from the dissociation of lead chloride.

$\begin{eqnarray} Q_{sp} &=& [Pb^{2+}][Cl^-]^2 \\ 1.8 \times 10^{-5} &=& (s)(2s + 0.1)^2 \\ s &=& [Pb^{2+}] \\ &=& 1.8 \times 10^{-3} M \\ 2s &=& [Cl^-] \\ &\approx & 0.1 M \end{eqnarray} \nonumber$

Notice that the molarity of Pb2+ is lower when NaCl is added. The equilibrium constant remains the same because of the increased concentration of the chloride ion. To simplify the reaction, it can be assumed that [Cl-] is approximately 0.1M since the formation of the chloride ion from the dissociation of lead chloride is so small. The reaction quotient for PbCl2 is greater than the equilibrium constant because of the added Cl-. This therefore shift the reaction left towards equilibrium, causing precipitation and lowering the current solubility of the reaction. Overall, the solubility of the reaction decreases with the added sodium chloride.

(Video) 17.1 Common Ion Effect
##### Exercise $$\PageIndex{5}$$

Calculate the solubility of silver carbonate in a 0.25 M solution of sodium carbonate. The solubility of silver carbonate in pure water is 8.45 × 10−12 at 25°C.

2.9 × 10−6 M (versus 1.3 × 10−4 M in pure water)

A Video Discussing the Common Ion Effect in Solubility Products: The Common Ion Effect in Solubility Products (opens in new window) [youtu.be]

## References

1. Harwood, William S., F. G. Herring, Jeffry D. Madura, and Ralph H. Petrucci. General Chemistry Principles and Modern Applications. 9th ed. New Jersey: Prentice Hall, 2007.
(Video) Common ion effect and buffers | Chemistry | Khan Academy

## Contributors and Attributions

• Emmellin Tung, Mahtab Danai (UCD)
• Jim Clark (ChemGuide)
• Chung (Peter) Chieh (Professor Emeritus, Chemistry @University of Waterloo)

## FAQs

### What is the common ion effect in acid base equilibria? ›

The common ion effect suppresses the ionization of a weak acid by adding more of an ion that is a product of this equilibrium. Adding a common ion to a system at equilibrium affects the equilibrium composition, but not the ionization constant.

How do you find the common ion effect? ›

H2S ⇌ H+ + HS. If HCl is added to the H2S solution, H+ a common ion and creates a common ion effect. Due to the increase in concentration of H+ ions from the added HCl, the equilibrium of the dissociation of H2S shifts to the left and keeps the value of Ka constant.

What is the common ion effect How does Le Chatelier's principle explain it? ›

The common-ion effect is an application of Le Chatelier's Principle to solubility equilibria. The solubility of a slightly soluble salt is decreased when a common ion (in the form of another, more soluble, salt) is added. For salts that contain an acidic or basic ion, pH can also affect solubility.

What is common ion effect short answer? ›

The common ion effect is an effect that suppresses the ionization of an electrolyte when another electrolyte (which contains an ion which is also present in the first electrolyte, i.e. a common ion) is added. It is considered to be a consequence of Le Chatlier's principle (or the Equilibrium Law).

What is the common ion effect quizlet? ›

The Common Ion Effect. The suppression of the ionization of a weak acid or a weak base by the presence of a common ion from a strong electrolyte. The solubility of a slightly soluble ionic compound is LOWERED when a second solute that furnishes a common ion is added to the solution.

What is the basic equilibrium equation? ›

The equilibrium equations (balance of linear momentum) are given in index form as(1.4)σji,j+bi=ρu¨i,i,j=1,2,3where σij are components of (Cauchy) stress, ρ is mass density, and bi are body force components.

What is an acid-base reaction formula? ›

General acid-base reactions, also called neutralization reactions can be summarized with the following reaction equation: ACID(aq) + BASE(aq) ⟶ H2O(l) + SALT(aq) or (s)

What is acid-base equilibria reaction? ›

Proton transfer reactions in acid-base equilibria

Acid-base chemistry is a transactional process in which protons are exchanged between two chemical species. A molecule or ion that loses or "donates" a proton is acting as an acid ; a species that receives or "accepts" that proton plays the role of a base .

What is common ion effect with one example? ›

The common ion effect causes the reduction of solubility when adding like ions. An example of the common ion effect is when sodium chloride (NaCl) is added to a solution of HCl and water. The hydrochloric acid and water are in equilibrium, with the products being H3 O+ and Cl- .

Why is it called the common ion effect? ›

Sodium chloride shares an ion with lead(II) chloride. The chloride ion is common to both of them; this is the origin of the term "common ion effect".

### How do you find the most common ion charge of an element? ›

To find the ionic charge of an element you'll need to consult your Periodic Table. On the Periodic Table metals (found on the left of the table) will be positive. Non-metals (found on the right) will be negative.

Why is the common ion effect and buffer just examples of Le Chatelier's principle? ›

It play a vital role in regulation of buffers. Addition of excess ions will alter the pH of buffer solution. Therefore, the common ion effect takes role in pH regulation. According to Le Chatelier's principle, addition of more ions alters the equilibrium and shifts the reaction to favor solid or deionized ion.

What are the 3 factors that affect the Le Chatelier's principle? ›

Factors affecting equilibrium-Le Chatelier's principle
• Changes in concentration.
• Changes in pressure.
• Changes in temperature.

What ion causes the equilibrium to shift? ›

The "stress" must be explained only in terms of the species present in the equilibrium reaction equation: sulfuric acid is a source of hydrogen ions and it is an increase in the hydrogen ion concentration that causes the equilibrium to shift.

How does common ion effect affect pH? ›

Common Ion Effect in Buffer Solutions

The generated common ions will counteract the ionization of the acid. Due to Le Chatelier's Principle, the equilibrium will shift to favor the reactants (to the left). The pH increases because the ionization (and dissociation) of the acid is decreases.

Which is not an example of common ion effect? ›

Updated On: 27-06-2022. Common ion effect is the suppression of degree of dissociation of a weak electrolyte in the presence of a strong electrolyte having common ion . Among the given , CH3COOH+NaOH has no common ion , thus does not exhibit common ion effect .

What does the common ion effect promote? ›

An unusual common ion effect promotes dissolution of metal salts in room-temperature ionic liquids: a strategy to obtain ionic liquids having organic–inorganic mixed cations.

What is common ion effect write its two application? ›

The common ion effect is employed in the purification of substances, treatment of water, salting out in soap formation, and quantitative analysis.

What is the definition of a common ion as it applies? ›

In simpler terms, it is an effect that prevents one electrolyte from ionizing when another electrolyte is introduced. It is thought to be a result of Le Chatelier's principle. The term "common-ion effect" refers to the influence on an equilibrium caused by adding an ion already present in the solution.

What is the common ion in both NaCl and KCl? ›

When NaCl and KCl, both very soluble salts, are dissolved in the same solution, the Cl ions are common to both salts. In a system containing NaCl and KCl, the Cl ions are common ions.

### What are the 3 equations of equilibrium? ›

In order for a system to be in equilibrium, it must satisfy all three equations of equilibrium, Sum Fx = 0, Sum Fy = 0 and Sum M = 0. Begin with the sum of the forces equations.

What are the 3 types of equilibrium? ›

There are three types of equilibrium: stable, unstable, and neutral. Figures throughout this module illustrate various examples. Figure 1 presents a balanced system, such as the toy doll on the man's hand, which has its center of gravity (cg) directly over the pivot, so that the torque of the total weight is zero.

How do you solve equilibrium reactions? ›

Solution
1. STEP 1: Fill in the given concentrations.
2. STEP 2: Calculate the change concentrations by using a variable 'x'
3. STEP 3: Calculate the concentrations at equilibrium.
May 22, 2019

How do you identify an acid-base reaction example? ›

To decide whether a substance is an acid or base, count the hydrogens on each substance before and after the reaction. If the number has decreased that substance is the acid (which donates hydrogen ions) . If the number of hydrogens has increased that substance is the base (accepts hydrogen ions).

What are the two types of equilibria? ›

There are two types of chemical equilibrium:
• Homogeneous Equilibrium.
• Heterogeneous Equilibrium.

What are the three types of acid base reactions? ›

What type of reactions involve acids and bases?
• acid and metal hydroxide (neutralisation)
• acid and metal.
• acid and metal oxide.
• acid and metal (hydrogen) carbonate.

What can you learn from acid base equilibrium? ›

Learning Outcomes for Acid/Base Equilibria

Identify strong and weak acids and bases. Identify acid/base conjugate pairs and their relative strengths. Understand the process of auto-ionization of water and what is meant by acidic, basic, and neutral.

Which will not show common ion effect on addition of HCl? ›

Top Courses for NEET

Which will not show common ion effect on addition of hcl among ch3cooh, h2s ,c6h5cooh and h2so4? Please explain? It's h2so4 ... because h2so4 is a strong acid and it will dissociate completely...

What is the importance of common ion effect in qualitative analysis? ›

Ans : The addition of a common ion prevents the weak acid or weak base from ionising as much as it would otherwise if the common ion were not present. The common ion effect prevents the ionisation of a weak acid from occurring by increasing the concentration of an ion that is produced as a result of this equilibrium.

What's the common ion present in acids? ›

Acids are composed primarily of hydrogen ions and a non-metallic anion. Bases are composed primarily of hydroxyl ions and a metallic cation.

### What is common ion effect PDF? ›

The common-ion effect is used to describe the effect on an equilibrium involving a substance that adds an ion that is a part of the equilibrium. Adding a common ion prevents the weak acid or weak base from ionizing as much as it would without the added common ion.

What charge does Group 17 have? ›

Therefore, each element requires only one electron to attain the nearest noble gas configuration. Thus, the charge on ions formed by group 17 element is -1.

How do you know how many of each ion will be needed in an ionic compound? ›

Each ion has a single charge, one positive and one negative, so we need only one ion of each to balance the overall charge. When writing the ionic formula, we follow two additional conventions: (1) write the formula for the cation first and the formula for the anion next, but (2) do not write the charges on the ions.

How do you determine the charge of an ion example? ›

Number of protons - number of electrons = charge on ion. 3protons - 2 electrons = 1+ Page 16 Number of protons - number of electrons = charge on ion.

What is the common ion of acid and base? ›

Ions make up all acids and bases. Acids are composed primarily of hydrogen ions and a non-metallic anion. Bases are composed primarily of hydroxyl ions and a metallic cation. As we can see, both acids and bases are electrolytes because they are made up of ions.

What is the effect of ionic strength on equilibria? ›

As the ionic strength increases, an ion loses some of its effectiveness, and its activity coefficient decreases. 2. In solutions that are not too concentrated, the activity coefficient for a given species is independent of the nature of the electrolyte and dependent only on the ionic strength.

What is common ion effect explain with example? ›

The reduction of the degree of dissociation of a salt by the addition of a common-ion is called the common ion effect. E.g.: In a saturated solution of silver chloride, we have the equilibrium: AgCl(aq)⇌Ag++Cl−

What happens in an acid base equilibrium? ›

In any acid-base reaction, the equilibrium will favor the reaction that moves the proton to the stronger base. This equilibrium constant is referred to as the ion-product constant for water, Kw. At 25°C, Kw = 1.0 × 10−14 Water is amphoteric. In pure water, some molecules act as bases and some as acids.

What is the importance of common ion effect? ›

The common-ion effect plays important roles in controlling the pH of a solution, determining the solubility of a slightly soluble salt and thus can control the formation of a precipitate by either reversing the dissociation of the acid, if the acid had already dissociated or reducing the dissociation [10] if the salt ...

What two ions are important in acid base? ›

The most important pH buffer system in the blood involves carbonic acid (a weak acid formed from the carbon dioxide dissolved in blood) and bicarbonate ions (the corresponding weak base).

### What is the common ion in all acids? ›

Acids are mainly made up of hydrogen ions and a non-metallic anion.

What are the factors affecting equilibria? ›

The temperature, pressure, and concentration of the system are all factors that affect equilibrium. When one of these factors changes, the equilibrium of the system is disrupted, and the system readjusts itself until it returns to equilibrium.

What happens when ionic strength increases? ›

Firstly as the ionic strength is increased the current increases. This leads to heating effects resulting from the inability to dissipiate heat. The effects manifest as noise and baseline disturbances. For this reason the ionic strength should be minimised to prevent noise resulting from high currents.

How increasing ionic strength affects the rate constant? ›

The increase of the ionic strength of the medium alters the ionic atmosphere and changes the charge densities around the anions. Consequently, there is an increment of the rate constants for higher ionic strengths.

What is the opposite of the common ion effect? ›

The Diverse Ion Effect (The Salt Effect)

A sparingly-soluble salt will be more soluble in a solution that contains non-participating ions. This is just the opposite of the common ion effect, and it might at first seem rather counter-intuitive: why would adding more ions of any kind make a salt more likely to dissolve?

What does equilibrium favor in an acid-base reaction? ›

Equilibrium in acid-base reactions always favors the weaker side. In the following example the pKa values for the substances acting as acids are shown under their structures. Equilibrium favors the left side because the substances on the left are the weaker acid and the weaker base.

What happens in an equilibrium reaction? ›

At equilibrium, the two opposing reactions go on at equal rates, or velocities, and hence there is no net change in the amounts of substances involved.

What is a basic equilibrium equation? ›

The equilibrium equation describes the static or dynamic equilibrium of all internal and external forces of the system. In the static case, the equilibrium equation is. [6.23] K · u = F. where K is the stiffness matrix of the system, u is the vector with the nodal displacements and F represents the external forces (Fig ...

## Videos

1. 17.1 The Common Ion Effect
(FusChemistryVideos)
2. CHE 1093 Class 6B 1 Common Ion Effect in Acid Base Equilibria
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3. 17.1 The Common Ion Effect
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4. acid-base equilibrium - common ion effect
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5. 17.13 Acid Base Equilibrium - Common Ion Effect
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6. Buffer Solutions
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