Salt bridge notation

Standard Hydrogen Electrode The standard hydrogen electrode (SHE) is rarely used for routine analytical work, but is important because it is the reference electrode used to establish standard-state potentials for other half-reactions. The SHE consists of a Pt electrode immersed in a solution in which the hydrogen ion activity is 1.00 and in which H2 gas is bubbled at a pressure of 1 atm (Figure 11.7). A conventional salt bridge connects the SHE to the indicator half-cell. The shorthand notation for the standard hydrogen electrode is... 

The saturated calomel electrode (SCE), which is constructed using an aqueous solution saturated with KCl, has a potential at 25 °C of -hO.2444 V. A typical SCE is shown in Eigure 11.8 and consists of an inner tube, packed with a paste of Hg, HgiCli, and saturated KCl, situated within a second tube filled with a saturated solution of KCl. A small hole connects the two tubes, and an asbestos fiber serves as a salt bridge to the solution in which the SCE is immersed. The stopper in the outer tube may be removed when additional saturated KCl is needed. The shorthand notation for this cell is... 

A typical Ag/AgCl electrode is shown in figure 11.9 and consists of a silver wire, the end of which is coated with a thin film of AgCl. The wire is immersed in a solution that contains the desired concentration of KCl and that is saturated with AgCl. A porous plug serves as the salt bridge. The shorthand notation for the cell is... 

Consider a salt bridge cell in which the anode is a manganese rod immersed in an aqueous solution of manganese(II) sulfate. The cathode is a chromium strip immersed in an aqueous solution of chromium(in) sulfate. Sketch a diagram of die cell, indicating the flow of the current throughout. Write the half-equations for the electrode reactions, the overall equation, and die abbreviated notation for the celL... 

Finally, we note that the two half-cells must communicate somehow - they must be connected. It is common practice to assume that a salt bridge has been incorporated, unless stated otherwise, so we join the notations for the two half-cell with a double vertical line, as... 

In cell notation, be sure to write anode, anode compartment, salt bridge, cathode compartment, cathode in this specific order. 

Fig. 4. C-terminal salt bridges and the role of the residue F9j8 in the T and R structures of mammalian and fish hemoglobins, (a) Human T structure (b) human R structure (c) carp T structure (d) carp R structure. The letters F, G, and H denote helical segments FG, GH, and HC denote nonhelical segments. The same notation is used in Fig. 5 (23).

Use the shorthand notation (page 498) to describe the cells in Problem 19-9. Each cell is supplied with a salt bridge to provide electrical contact between the solutions in the two cell compartments. 

Problem Draw a diagram, show balanced equations, and write the notation for a voltaic cell that consists of one half-cell with a Cr bar in a Cr(N03)3 solution, another half-cell with an Ag bar in an AgN03 solution, and a KNO3 salt bridge. Measurement indicates that the Cr electrode is negative relative to the Ag electrode. 

FOLLOW-UP PROBLEM 21.2 In one compartment of a voltaic cell, a graphite rod dips into an acidic solution of K2Cr207 and Cr(N03)3 in the other compartment, a tin bar dips into a Sn(N03)2 solution. A KNO3 salt bridge joins them. The tin electrode is negative relative to the graphite. Draw a diagram of the cell, show the balanced equations, and write the cell notation. 

A voltaic cell consists of oxidation (anode) and reduction (cathode) half-cells, connected by a wire to conduct electrons and a salt bridge to maintain charge neutrality as the cell operates. Electrons move from anode (left) to cathode (right), while cations move from the salt bridge into the cathode half-cell and anions from the salt bridge into the anode half-cell. The cell notation shows the species and their phases in each half-cell, as well as the direction of current flow. 

We now will introduce a handy line notation used to describe electrochemical cells. In this notation the anode components are listed on the left and the cathode components are listed on the right, separated by double vertical lines (indicating the salt bridge or porous disk). For example, the line notation for the cell described in Example 18.3(a) is... 

The half-reactions are often represented by the notation shown below. By convention, the oxidation reaction is written on the left of the symbol denoting the salt bridge, and the reduction reaction is written on the right side of the salt bridge symbol. 

A double vertical line represents a salt bridge or a porous barrier. A single vertical line represents a change in phase, such as from solid to solution, (a) Write the half-reactions and overall cell reaction represented by Fe Fe Ag Ag sketch the ceU. (b) Write the half-reactions and overall ceU reaction represented by Zn Zn H H2 sketch the ceU. (c) Using the notation just described, represent a cell based on the following reaction ... 

If the electrochemical chain includes several successive electrolyte media, then the abbreviated notation 11 is often used to denote the separation zone between two electrolytes. Such a notation represents either the porous material filled with a mixture of the two liquid electrolytes, or all of the various phases of a salt bridge (see example below). The nature of this intermediate zone is often such that the global zero current junction voltage can be neglected... 

Because there are so many possible electrochemical cells, a shorthand notation for representing their specific chemistry has been devised. This cell notation lists the metals and ions involved in the reaction. A vertical line,, denotes a phase boundary, and a double line, H, represents the salt bridge. The anode is always written on the left, and the cathode on the right ... 

Ions in the salt bridge are not part of the reaction so they are not in the notation. 

In this notation, the anode, or oxidation half-cell, is always written on the left the cathode, or reduction half-cell, is written on the right. The two electrodes are electrically connected by means of a salt bridge, denoted by two vertical bars. 

Give the notation for a voltaic cell constructed from a hydrogen electrode (cathode) in 1.0 M HCl and a nickel electrode (anode) in 1.0 M NiS04 solution. The electrodes are connected by a salt bridge. 

A voltaic cell has an iron rod in 0.30 M iron(in) chloride solution for the cathode and a zinc rod in 0.40 M zinc sulfate solution for the anode. The half-cells are connected by a salt bridge. Write the notation for this cell. 

The double line represents the salt bridge, or porous barrier, between the two half-cells. For the present cell, the cell notation is... 

One often wishes to describe a galvanic cell without taking the trouble to draw an actual picture of it. The notation used is a rudimentary diagram of the cell. Phase boundaries (between solid and liquid, liquid and gas, or solid and gas) are indicated by a liquid junction is represented by, a salt bridge by. The cells previously discussed may be represented thus (with spaces for filling in the concentrations) ... 

It follows that if sensible measurements are to be made to find the standard electrode potential of the Fe /Fe couple, the two half cells must be separated using a salt bridge as shown in Fig. 4.2 and summarised by the cell notation... 

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