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Acids and Bases

Investigation 3 – PreLab

 

 

 

 

 

 

 

BRANCH OUT

Clean water is essential for everyday life. Water treatment plant and system operators ensure that the water pumped from rivers, streams, and reservoirs is clean and has a safe pH before it gets to your home.

GET FOCUSED

This Investigation is designed to help you to answer the following Focus Question:

  • What happens to the concentration of hydrogen ions (H+) when an acid and a base are reacted? 

Note: This question is located in your SDR at the beginning and end of the Investigation.

GO DEEPER

As a class, read the Background(s) in the Investigation. When finished, discuss the following concepts as a class:

  • The concentration of hydrogen ions (H+) in acidic solution can be decreased by diluting the solution.
  • Another way to decrease the concentration of H+ ions in a solution is to perform a chemical reaction by dissolving both an acid and a base in water.
  • Discuss the following equation illustrating that hydrochloric acid, like all acids, dissociates into H+ ions and a negatively charged ion like Cl when dissolved in water.

Acids 3 Pre Equation 1

  • Discuss the following equation illustrating that sodium hydroxide, like all bases, dissociates into OH ions and a positively charged ion like Na+ when dissolved in water.

Acids 3 Pre Equation 2

  • Discuss the following equation illustrating the neutralization reaction between hydrochloric acid and sodium hydroxide to produce water and NaCl.

Acids 3 Pre Equation 3

  • If the acid concentration is higher than the concentration of the base, then the H+ concentration will be high and the pH will remain in the acidic range.
  • If the concentrations of the acid and base are equal, the pH will be in the neutral range, approximately 7.
  • If the base concentration is higher than the acid concentration, then the H+ concentration will be very low and the pH will be in the basic range.
  • Discuss the following equation describing the neutralization reaction. The reaction consumes two acid molecules and produces two water molecules because unlike NaOH, Mg(OH)2 possesses two OH ions.

Acids 3 Pre Equation 4

 

LEARN THE LabLearner LINGO

The following Key Term is introduced in the Investigation Background(s). It should be used, as appropriate, by teachers and students during everyday classroom discourse.

  • neutralization

Note: The definition of this term can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

  • Complete the Recall section in your SDR. 
    • What is the relationship between the pH of a solution and the concentration of hydrogen ions (H+)?  
    • When the pH is low, is the concentration of hydrogen ions (H+) low or high?
    • When the pH is high, is the concentration of hydrogen ions (H+) low or high?
    • How can the concentration of hydrogen ions (H+) be changed?
  • This Investigation will help you to understand what happens to the concentration of hydrogen ions (H+) when an acid and base react.
  • Play the video below. Remember to follow along with your SDR and make any notes that you think might be helpful to you in the lab.
  • After the video, divide into lab groups to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

For homework, you should review the Investigation and video in preparation for the Lab.