Types Of Equilibria
Category : JEE Main & Advanced
The equilibrium between different chemical species present in the same or different phases is called chemical equilibrium. There are two types of chemical equilibrium.
(1) Homogeneous equilibrium : The equilibrium reactions in which all the reactants and the products are in the same phase are called homogeneous equilibrium reactions.
\[{{C}_{2}}{{H}_{5}}OH\,(l)+C{{H}_{3}}COOH\,(l)\]? \[C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}\,(l)+{{H}_{2}}O(l)\]
\[{{N}_{2}}\,(g)+3{{H}_{2}}\,(g)\] ? \[2N{{H}_{3}}(g)\]
\[2S{{O}_{2}}\,(g)+{{O}_{2}}\,(g)\] ? \[2S{{O}_{3}}(g)\]
(2) Heterogeneous equilibrium : The equilibrium reactions in which the reactants and the products are present in different phases are called heterogeneous equilibrium reactions.
\[2NaHC{{O}_{3}}\,(s)\]? \[N{{a}_{2}}C{{O}_{3}}\,(s)+C{{O}_{2}}\,(g)+{{H}_{2}}O\,(g)\]
\[Ca{{(OH)}_{2}}(s)+{{H}_{2}}O\,(l)\] ? \[C{{a}^{2+}}(aq)+2O{{H}^{-}}\,(aq)\]
\[CaC{{O}_{3}}\,(s)\] ? \[CaO\,(s)+C{{O}_{2}}\,(g)\]
\[{{H}_{2}}O\,(l)\] ? \[{{H}_{2}}O\,(g)\]
Homogeneous equilibria and equations for equilibrium constant (Equilibrium pressure is P atm in a V L flask)
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\[\Delta n=0\,;\,\,{{K}_{p}}={{K}_{c}}\] |
\[\Delta n<0\] ; \[{{K}_{p}}<{{K}_{c}}\] |
\[\Delta n>0;\ {{K}_{p}}>{{K}_{c}}\] |
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\[\underset{(g)}{\mathop{{{H}_{2}}}}\,\]+ \[\underset{(g)}{\mathop{{{I}_{2}}}}\,\] ? \[\underset{(g)}{\mathop{2HI}}\,\] |
\[\underset{(g)}{\mathop{{{N}_{2}}}}\,+\underset{(g)}{\mathop{3{{H}_{2}}}}\,\]? \[\underset{(g)}{\mathop{2N{{H}_{3}}}}\,\] |
\[\underset{(g)}{\mathop{2S{{O}_{2}}}}\,+\underset{(g)}{\mathop{{{O}_{2}}}}\,\]?\[2\underset{(g)}{\mathop{S{{O}_{3}}}}\,\] |
\[\underset{(g)}{\mathop{PC{{l}_{_{5}}}}}\,\]?\[\underset{(g)}{\mathop{PC{{l}_{3}}}}\,+\underset{(g)}{\mathop{C{{l}_{2}}}}\,\] |
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Initial mole |
1 1 0 |
1 3 0 |
2 1 0 |
1 0 0 |
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Mole at Equilibrium |
(1–x) (1– x) 2x |
(1–x) (3–3x) 2x |
(2–2x) (1–x) 2x |
(1–x) x x |
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Total mole at equilibrium |
2 |
(4 – 2x) |
(3 – x) |
(1 + x) |
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Active masses |
\[\left( \frac{1-x}{V} \right)\] \[\left( \frac{1-x}{V} \right)\] \[\frac{2x}{V}\] |
\[\left( \frac{1-x}{V} \right)\] \[3\,\left( \frac{1-x}{V} \right)\] \[\left( \frac{2x}{V} \right)\] |
\[\left( \frac{2-2x}{V} \right)\] \[\left( \frac{1-x}{V} \right)\] \[\left( \frac{2x}{V} \right)\] |
\[\left( \frac{1-x}{V} \right)\] \[\left( \frac{x}{V} \right)\] \[\left( \frac{x}{V} \right)\] |
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Mole fraction |
\[\left( \frac{1-x}{2} \right)\] \[\left( \frac{1-x}{2} \right)\] \[\frac{2x}{2}\] |
\[\frac{1-x}{2\,\left( 2-x \right)}\]\[\frac{3}{2}\left( \frac{1-x}{2-x} \right)\]\[\frac{x}{(2-x)}\] |
\[\left( \frac{2-2x}{3-x} \right)\] \[\left( \frac{1-x}{3-x} \right)\,\,\ \ \left( \frac{2x}{3-x} \right)\] |
\[\left( \frac{1-x}{1+x} \right)\] \[\left( \frac{x}{1+x} \right)\] \[\left( \frac{x}{1+x} \right)\] |
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Partial pressure |
\[p\,\left( \frac{1-x}{2} \right)\]\[p\,\left( \frac{1-x}{2} \right)\] \[p\,\left( \frac{2x}{2} \right)\] |
\[P\left( \frac{1-x}{2(2-x)\_} \right)\,P\,\left( \frac{3(1-x)}{2(2-x)} \right)\,\frac{Px}{(2-x)}\] |
\[P\,\left( \frac{2-2x}{3-x} \right)\] \[P\left( \frac{1-x}{3-x} \right)\] \[P\,\left( \frac{2x}{3-x} \right)\] |
\[P\left( \frac{1-x}{1+x} \right)\] \[P\left( \frac{x}{1+x} \right)\] \[P\left( \frac{x}{1+x} \right)\] |
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\[{{K}_{c}}\]
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\[\frac{4{{x}^{2}}}{\left( 1-x \right){{\,}^{2}}}\] |
\[\frac{4{{x}^{2}}{{V}^{2}}}{27\,\,\left( 1-x \right){{\,}^{4}}}\] |
\[\frac{{{x}^{2}}V}{\left( 1-x \right){{\,}^{3}}}\] |
\[\frac{{{x}^{2}}}{\left( 1-x \right)\,V}\] |
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\[{{K}_{p}}\] |
\[\frac{4{{x}^{2}}}{\left( 1-x \right){{\,}^{2}}}\] |
\[\frac{16{{x}^{2}}\,\left( 2-x \right){{\,}^{2}}}{27\left( 1-x \right){{\,}^{4}}{{P}^{2}}}\] |
\[\frac{{{x}^{2}}\,\left( 3-x \right)\,}{P\,\left( 1-x \right){{\,}^{3}}}\] |
\[\frac{P{{x}^{2}}}{\left( 1-{{x}^{2}} \right)\,}\] |
Heterogeneous equilibria and equation for equilibrium constant (Equilibrium pressure is P atm)
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\[N{{H}_{4}}HS(s)\]?\[N{{H}_{3}}(g)\] + \[{{H}_{2}}S(g)\] |
\[C(s)+C{{O}_{2}}(g)\]?\[2CO(g)\] |
\[N{{H}_{2}}C{{O}_{2}}N{{H}_{4}}(s)\]?\[2N{{H}_{3}}(g)+C{{O}_{2}}(g)\] |
|
Initial mole |
1 0 0 |
1 1 0 |
1 0 0 |
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Mole at equilibrium |
(1–x) x x |
(1–x) (1–x) 2x |
(1–x) 2x x |
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Total moles at equilibrium (solid not included) |
2x |
(1+x) |
3x |
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Mole fraction |
\[\frac{x}{2x}=\frac{1}{2}\] \[\frac{1}{2}\] |
\[\left( \frac{1-x}{1+x} \right)\] \[\left( \frac{2x}{1+x} \right)\] |
\[\frac{2}{3}\] \[\frac{1}{3}\] |
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Partial pressure |
\[\frac{P}{2}\] \[\frac{P}{2}\] |
\[P\left( \frac{1-x}{1+x} \right)\] \[P\left( \frac{2x}{1+x} \right)\] |
\[\frac{2P}{3}\] \[\frac{P}{3}\] |
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\[{{K}_{p}}\] |
\[\frac{{{P}^{2}}}{4}\] |
\[\frac{4{{P}^{{}}}{{x}^{2}}}{(1-{{x}^{2}})}\] |
\[\frac{4{{P}^{3}}}{27}\] |
Relationship between equilibrium constant and DG°
DG for a reaction under any condition is related with DG° by the relation, \[\Delta G=\Delta G{}^\circ +2.303\ RT\log Q\]
Standard free energy change of a reaction and its equilibrium constant are related to each other at temperature T by the relation, \[\Delta {{G}^{o}}=-2.303\,RT\,\log K\]
For a general reaction \[aA+bB\] ? \[cC+dD\]
\[K=\frac{{{({{a}_{C}})}^{c}}\ {{({{a}_{D}})}^{d}}}{{{({{a}_{A}})}^{a}}\ {{({{a}_{B}})}^{b}}}\]
Where a represent the activity of the reactants and products. It is unit less.
For pure solids and liquids: \[a=1\].
For gases: \[a=\] pressure of gas in atm.
For components in solution: \[a=\] molar concentration.
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