Indicators and pH Lab

Today, we learned/recalled that we can determine the acidity or alkalinity of an aqueous solution by different indicators.


1. The pH meter - It is an electronic device that shows a numerical value of how acidic or basic a solution is. It is accurate and fast, but is also relatively expensive.


2. The Indicator Paper - It is an ordinary filter paper that changes colour when the concentration of hydrogen ions reach a certain level.


3. The Indicator Solutions - The different indicator solutions change colour at a specific pH.




We also had a lab today. It is the prettiest lab that we did and will do, as Mrs. Kozoriz noted. (And yes, it really turned out beautiful!) We placed 10 drops of distilled water in column numbers 2-11 and added either HCl or NaOH to the rows. And then, using the indicator solutions that were provided to us, we witnessed the transformation of colours in each of the wells of our well plates.







After the fun, we had four questions to answer:


1. What is the significance of the colour changes in each row?
2. Which would be a good indicator for general use?
3. Which would be a good indicator for a HCl/NaOH titration?
4. Which would be a poor indicator for a HCl/NaOH titration? Why?


Labs are due tomorrow! I choose Marie as the next scribe :)

Wednesday, February 25th

At the beginning of class, Mrs. K handed our titration lab back. When doing labs, she reminded us to do what has been asked, like stating the purpose of the lab, the qualitative observations of the substances involved, and the calculations of how we got our answers.


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We also reviewed what a Redox Reaction is and the definition of an Oxidation Reaction and a Reduction Reaction.

A Redox Reaction is a reaction wherein oxidation and reduction occur at the same time.


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Next up, Ms. K showed us an experiment involving a Redox Reaction where:

1. She added copper (II) chloride to a beaker of water.
   
2. Because of that, the water turned blue-green.
   
3. She got a piece of crumpled aluminum foil and placed it inside the beaker.
   
4. After a few minutes, the aluminum started to have a dark orange colour and it little by little dissolved away.

What happened:
The aluminum lost electrons and the copper gained electrons.


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For the remainder of the class, we worked on the questions in the booklet and the worksheet as practice for determining the oxidation number of atoms; and indicating the element reduced, the element oxidized, the oxidizing agent, and the reducing agent.

• An oxidized element increases its oxidation number because it loses electrons.
  
• A reduced element decreases its oxidation number because it gains electrons.
• An oxidizing agent is a chemical compound contains the atom that gains electrons in a redox reaction.
• A reducing agent is a chemical compound that contains the atom that loses electrons in a redox reaction.

That's it for now.

The next scribe will be MARIE :)