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Standard Hydrogen Electrode

Discusses how reduction potential of half-cells are determined.

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Setting the Standard

Setting the Standard

Credit: Mark Hillary
Source: http://www.flickr.com/photos/markhillary/829573216/
License: CC BY-NC 3.0

If you buy a gallon of milk in Salem, Virginia, will you get the same amount that you would receive in Salem, Oregon? Long years ago, the answer would probably be “no”. Local merchants had no good standards, so did the best they could in measuring out items. Today we have federal and state agencies that determine the standards for measurement. These agencies are also linked to international organizations involved in setting standards for measurement.

Why It Matters

  • Measurement of electron flow in a reaction is an important part of many branches of chemistry. In order to make sure everyone is talking about the same process, the standard hydrogen electrode is used. This device allows scientists anywhere in the world to have a baseline for comparison for their results.
  • How reliable is the meter stick you use in your laboratory? To be perfectly comfortable, you would need to travel to Paris, France, to check your measurements with the official standard at the BIPM: Bureau International des Poids et Mesures(International Bureau of Weights and Measures). This meter standard was established in 1889. Today there are more precise ways to define the meter, but the prototype bar still exists.
  • One of the first phrases a beginning language student may learn is how to say “What time is it?” in the language being studied. This is not an idle question when you need to catch a plane at a specific time or you want to find out if your favorite restaurant is open yet. The world has moved far beyond the unreliable hourglasses of previous centuries. The “atomic clock” of today is a complex device based on electron transitions between energy levels. The accuracy of today’s atomic clocks is about one second in twenty million years.
  • Credit: Joi Ito
    Source: http://www.flickr.com/photos/joi/432273311/
    License: CC BY-NC 3.0

    Business is increasingly international, and it is extremely important for time to be consistent between different trading nations. It would not be good for deliveries to arrive at unexpected times [Figure2]


  • Watch a video about measurements at the link below:


Show What You Know

Use the links below to learn more about measurement standards. Then answer the following questions.

  1. When was the standard meter defined?
  2. What was the first definition of the standard meter?
  3. What does NIST stand for?
  4. What is the role of NIST?
  5. What isotope is used in the atomic clock?
  6. What do we actually measure when shooting a laser beam at the moon?

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Image Attributions

  1. [1]^ Credit: Mark Hillary; Source: http://www.flickr.com/photos/markhillary/829573216/; License: CC BY-NC 3.0
  2. [2]^ Credit: Joi Ito; Source: http://www.flickr.com/photos/joi/432273311/; License: CC BY-NC 3.0

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