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How Can the Electrical Conductivity of a Solution Be Tested?

Ionic compounds conduct electricity when dissolved in water. When an electric current is applied, they separate into positively and negatively charged ions. These compounds are called electrolytes and consist of acids, bases and salts. Each electrolyte has a different level of conductivity, which can be measured. Conductivity of ionic solutions is tested by measuring the amount of ions present in the solution.

  1. Electrolytes

    • Electrolytes are classified as strong or weak. Strong electrolytes are ionic compounds that fully dissociate in water. For example, in a hydrochloric acid solution, hydrogen fully separates from chloride and the solution has a high ion concentration. Thus, strong electrolytes conduct more electricity as ions transport the electric charge. In weak electrolytes, ions only partially dissociate, hence they have a lower electrical conductivity as less ions are present in solution.

    Circuit

    • An electric circuit is the most straightforward method for testing conductivity. The set up includes two metal rods or electrodes placed into a solution, far enough apart to not touch each other. A battery is connected to the electrodes to provide current and a voltmeter to measure voltage. Positive ions travel to the negative electrode or cathode, while negative ions travel to the anode, which is the positive electrode. Voltmeter readings provide information on solution conductivity.

    Circuit Specifications

    • Electrical conductivity is affected by the overall circuit design. Iron rods are commonly used as electrodes since they are good electrical conductors, although better conductors are available, such as aluminum and silver. The size and distance between the electrodes are important as conductance increases with increased size and closer distance. The voltmeter must also be correctly connected with the positive battery terminal attached to the red probe and the negative terminal to the black probe.

    Conductivity Titrations

    • Titrations involve the mixing of two solutions to the point of complete reaction, usually represented by a color change. This method is often used to determine conductivity of the titration end product. A classic example is an acid-base titration, which produces a salt solution and water. The electrical conductivity is tested by measuring the ion concentration of the salt solution using a standardized conductivity meter. Conductivity is measured in decisiemens per meter.

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