Notation for a Voltaic Cell

A useful shorthand notation describes the components of a voltaic cell. For exam- 

The components of the anode compartment (oxidation half-cell) are written to the left of the components of the cathode compartment (reduction half-cell). 

SAMPLE PROBLEM 21.2 Describing a Voltaic Cell with Diagram and Notation 

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. 

Plan From the given contents of the half-cells, we can write the half-reactions. We must determine which is the anode compartment (oxidation) and which is the cathode (reduction). To do so, we must find the direction of the spontaneous redox reaction, which is given by the relative electrode charges. Electrons are released into the anode during oxidation, so it has a negative charge. We are told that Cr is negative, so it must be the anode and, therefore, Ag is the cathode. 

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Describe the physical makeup of a voltaic cell, and explain the direction of electron flow draw a diagram and write the notation for a voltaic cell ( 21.2) (SP 21.2) (EPs 21.13-21.23)... 

Writing the cell reaction from the cell notation Given the notation for a voltaic cell, write the overall cell reaction (EXAMPLE 20.4). Alternatively, given the cell reaction, write the cell notation. 

Write the cell notation for a voltaic cell with the following half-reactions. 

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. 

Give the notation for a voltaic cell that uses the reaction... 

A single vertical line represents a phase boundary. For example, Zn(s) Zn iaq) indicates that the solid Zn is a different phase from the aqueous Zn " ". A comma separates the half-cell components that are in the same phase. For example, the notation for the voltaic cell housing the reaction between I and Mn04 shown in Figure 21.6 is... 

Write the half-reactions and the overall cell reaction for the following notation of a voltaic cell ... 

To fully specify a voltaic cell, it is necessary to give the concentrations of solutions or ions and the pressure of gases. In the cell notation, these are written within parentheses for each species. For example,... 

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. 

In some voltaic cells, there is no component in the half-reactions that can be used as an electrode. When this is the case, inert electrodes made of graphite or platinum are used for the transfer of electrons. If there are two ionic components in a cell, their symbols are separated by a comma. For example, suppose a voltaic cell consists of a platinum anode placed in a Sn " solution, and a silver cathode placed in a Ag solution. The notation for the ceU would be written as... 

Make a sketch of the voltaic cell represented by the line notation. Write the overall balanced equation for the reaction and calculate Hceii-... 

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