Applications of Adsorption
Importance or Applications of Adsorption: Some of the important applications of adsorption are as follows: (1) In the preparation of gas masks using activated charcoal to avoid poisonous gases like etc. (2) Froth floatation method used for concentration of sulphide ores is based on adsorption. (3) Silica gel can be used to remove moisture and to control humidity. (4) Ion exchange method used to soften water is based on adsorption. (5) Adsorption chromatography is used to purify and...
read moreLangmuir Adsorption Isotherm
Langmuir Adsorption Isotherm: According to Langmuir Adsorption Isotherm: On taking reciprocal, Here a, b are constants when a graph is plotted. Between and P. It is a straight line, in which slope is equal to b/a while intercept is equal to ...
read moreFreundlich Adsorption Isotherm
Freundlich Adsorption Isotherm: According to him: (i) At low pressure: At low pressure the graph is almost Straight. i.e. Where, K = constant (ii) At high pressure: x / m becomes almost constant and does not change with pressure (iii) At intermediate value of pressure. Here, …..(1) Here ‘n’ is a constant depending upon nature of adsorbate and adsorbent. The value of K, n can be determined as follows: On taking logarithm of equation (1) we get Thus, on plotting a graph between x/ m and...
read moreFactors Affecting Adsorption
Adsorption of gases on solid surface depends upon: (1) Nature of gas or adsorbent: Adsorption Critical temperature of gas or van der Waal’s force of attraction (a) (2) Effect of Temperature: Adsorption Since adsorption is exothermic. (3) Pressure : At constant Temperature (4) Surface area of Adsorbent: Larger the surface area of adsorbent more will be active centers and faster will be the rate of adsorption. (5) Activation of Solid Adsorbent: When adsorbent is sub-divided or already...
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The phenomenon of adsorption was introduced by Scheele during the discovery of uptake of gases by charcoal. Lowitz found that charcoal could take up colouring matter from solutions as well. The term adsorption was given by Kayser The concept of adsorption was developed by Kayser and Raymonds. Definition: “The phenomenon of higher concentration at a surface brought about by the action of surface forces is known as adsorption”. Or It is the change in concentration in the interfacial layers between two...
read moreNernst Equation
It describes the quantitative relationship between electrode potential and concentrations and temperature of the substance involved in the half cell reaction. Consider a simple general reaction: Nemst deduced the following mathematical expression for the above reaction: where, E = Electrode potential of the metal, = standard electrode potential, R = gas constant, T = temperature in K, F = Faraday constant , n = number of electrons involved in the half reaction, [M] = activity of metal in the solid phase or liquid phase and is...
read moreStandard Electrode Potential
It is potential difference developed between metal electrode and the ions of the solution of a molar concentration or 1 atm. pressure at 298 K [25°C]. It is denoted by . It is important to know that the absolute value of or or E cannot be determined as neither oxidation nor reduction reaction of half-cell occurs alone. Moreover we have to use a reference electrode i.e. an electrode with known value of electrode potential. The common reference electrode used is standard or normal hydrogen electrode which can work both as a cathode or an...
read moreElectrode Potential
When a metal rod is placed in a solution of metal ions the metal rod become oppositely charged to solution ions. As a result a potential develops between them. It is called electrode potential. E.g. Zn-rod becomes (-)vely charged in solution. In fact electrode potential is the tendency of a metal to loose or to gain electrons, i.e. It is measurement if tendency to get oxidize or to get reduced. It is denoted by E. The value of electrode potential depends upon: (A) Nature of electrode (B) Temperature (C) Concentration of ions in...
read moreSalt Bridge
Some of the importance of Salt bridge are listed below: (1). In Daniell cell electrons are released by anode and accepted by cathode. Therefore Zn changes into ion and changes into Cu. During this change there will be accumulation of charge near the two electrodes which prevents further flow of current. Due to this the electrochemical changes stop and current drops to zero. To prevent this, salt bridge is placed in between the two electrodes, In the presence of salt bridge, the charges flow towards the oppositely charged electrode. The...
read moreDaniel cell
The cells which produce electrical energy from chemical reactions are known as galvanic or voltaic cells. A galvanic cell in which one electrode is Zn plate in (or ion) solution and the other is Cu plate in ion) solution is called the Daniel cell. A schematic diagram of the cell is shown below: The two half reactions, I.e. At anode at cathode are made to take place simultaneously with the electron transfer occurring through an extemal conducting wire. The two solutions (i.e., ) are linked by an inverted U-shaped tube as salt bridge. The...
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