pH (Potential Hydrogen)

pH

Hey guys, welcome to this video on PH levels.

The pH value of a solution is a measure of its acidity. Most solutions have a pH value between zero and fourteen on the pH scale.

Solutions with a pH value of 7, at the middle of the pH scale, are called neutral. If a solution has a pH value smaller than seven, it’s called acidic. If the pH value is larger than seven, the solution is called basic or alkaline. For instance, vinegar has a pH value of 2.4 and is acidic, pure water has a pH value of seven and is neutral, and household bleach has a pH value of 13 and is basic.

Note a solution that is more acidic has a smaller pH value. That has to do with the definition of pH. Generally, the acidity of a solution is defined by the concentration of hydronium ions in it. The higher the concentration of hydronium ions, the more acidic the solution. For instance, a solution with a 0.5 M concentration of hydronium ions is more acidic than a solution with a 0.05 M concentration of hydronium ions.

Let’s look at a few common substances and where they fall on the pH scale.

  • Battery acid, a very corrosive substance, is a strong acid, therefore it falls on the lower end of the pH scale with a pH of approximately one.
  • The gastric juices in your stomach, which help you to digest food, are acidic, too, with a pH value somewhere between 1.5 and 3.
  • Lemon juice contains a citric acid and has a pH value of two to three, just like vinegar.
  • Most soft drinks are quite acidic with pH values between 2.5 and 4. This is one of the reasons dentists don’t want you to drink soft drinks: the acid in soft drinks dissolves the enamel of your teeth. Milk is a lot better for your teeth, with a pH of approximately 6.5.
  • Rainwater is somewhat acidic, with a pH of approximately five. However, industrial pollutants can make rainwater more acidic, with a pH value anywhere between 2 and 4, which can be damaging to plant life.
  • Pure water is neutral with a pH of seven.
  • Blood is slightly basic, with a pH value of 7.4.
  • Seawater has a pH value of approximately 8.
  • Solutions of baking soda are mildly basic with a pH value of 8.4, therefore baking soda is used to clean up small acid spills in chemistry labs.
  • Soapy water has a pH value of 9 to 10, which helps to remove the grease from your skin or from dirty dishes.
  • Just as strongly acidic solutions pose hazards, so does strongly basic solutions. Lye, oven cleaner and household bleach have a pH value of approximately 13, so be careful around them.
  • Thanks for watching this overview of pH levels. See you guys next time!

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by Mometrix Test Preparation | Last Updated: August 21, 2019