Lab Report 5-1B: Acids and Bases Rita Kim Riverside

Lab 5-1B: Properties of Acids and Bases

         Purpose

 The purpose of this lab was to explore the different properties of the provided solutions and in turn investigate their acidity and basicity by using various pH indicators (Mg ribbon, red litmus, blue litmus, indigo carmine, bromothymol blue, methyl orange).   

             Materials:

4  x 6 spot plate

Masking tape

Solutions A, B, C, and D

4 pieces of Mg ribbon

4 pieces of red litmus paper

4 pieces of blue litmus paper

Bromothymol blue solution

Indigo carmine solution

Methyl orange solution

General Procedure (refer to page 230 in the textbook)

1.     Read through the procedure on page 230 of your BC Science 10 Textbook.  
2. Create a data table to record your results. Have a title for each column and row that will  clearly indicate each solution and each pH indicator.
3.  Label the 4 rows of your spot plate with A, B,C and D for each solution
4.   Place the corresponding solutions to their corresponding wells. Add only a few ML.
5.   Place each of the 6 different indicators in each of the four rows
6.   Observe the reactions
7.    Record your observations in your chart such as the colour.
8.    Ask your teacher for permission to clean up
9.    Clean up your area thoroughly

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Solutions 

Mg ribbon and Litmus paper

Results

MG Ribbon	Red Litmus	Blue Litmus	Bromothymol Blue	Indigo Carmine	Methyl Orange	Unknown
Bubbles formed on exposed metal	The indicator stayed red (same)	The indicator stayed the same colour (light pink)	The solution turned bright yellow	The solution turned into a very dark blue (almost black)	The solution turned light red	A
No fizzing	The indicator turned blue	The indicator turned light blue	The solution turned into a vibrant electric blue	The solution turned into a dark green	The solution stayed the same light/yellow orange	B
Bubbles formed on exposed metal	The indicator stayed red (same)	The indicator turned light blue	The solution turned into a deep dark blue	The solution turned into a medium dark blue	The solution turned vibrant/bright orange/red	C
No fizzing	The indicator stayed red (same)	The indicator turned light blue	The solution turned into a vibrant electric blue	The solution turned into a medium dark blue	The solution stayed the same light orange	D

Analyze

     1.The solutions in order from most acidic to least acidic is: solution A, solution C,  solution D and solution B.

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  2.The solution that I think was neutral is solution D. The results of the pH Indicators for this solution allowed me to interpret it’s acidity/basicity.  The red litmus paper stayed red (the same colour)  which means that it is either neutral or acidic. The blue litmus paper barely changed colour turning to a light blue. The bromothymol blue solution produced a blue colour therefore the pH range could be from 7.6 and higher. The Indigo Carmine solution produced a blue colour for which the pH range can be anything below 11.2. The methyl orange solution stayed yellow for the pH range is  above 4.4. The Mg ribbon didn't react. Through all these observations I can conclude that first Solution D is a base but that it is also the solution closest to being neutral since each pH indicator always stayed in the  range where the solution would be the closest to neural. Also looking at the other solutions I can right away eliminate solution B because in Indigo Carmine it turned green meaning that its pH range is either 11.2-13 which is very basic.  I can also eliminate solution A because in methyl orange the colour turned red meaning  it is within the range of anything below 3.2 which means it is very acidic.  And finally I can also eliminate Solution C because in methyl orange the solution turned a very bright orange that was almost red meaning that it was very acidic as well. Therefore I am left with solution D. 

    

3.The two bases in this lab were solution B and solution D (didn't react with Mg Ribbon). Solution B was more basic. The dead giveaway was that upon contact with indigo carmine the solution turned a dark green. When indigo carmine changes colour to green it means that the pH range is 11.2-13 which is very basic. Also  all the other indicators reinforced my hypothesis. The methyl orange stayed yellow.  The bromothymol blue stayed a deep blue. Both the red and blue litmus paper turned blue.  And since solution D didn't turn dark green in indigo carmine that means it wasn't alkaline/basic enough to have a ph range of 11.2-13 so clearly solution D is more basic since it did turn green. 

    

       4.   In general bases and metals do not react with one another while acids and metals react by creating a salt and hydrogen gas.  Magnesium metal helped us distinguish which solution was acidic or basic by allowing us to observe the reactions it had with the solutions. If the solution started producing bubbles upon contact that means that a chemical reaction took place between an acid and a metal.  

Conclude and Apply

1.

a) If the five indicators were in a solution that is pH 3 then red and blue litmus would be the colour red, bromothymol blue would be yellow, indigo carmine would be blue and methyl orange would be red.

b) If the five indicators were in a solution that is pH 10 then red and blue litmus would be the colour blue, bromothymol blue would be blue, indigo carmine would be blue and methyl orange would be yellow.

2. For my test kit I would take bromothymol blue solution to help me identify a neutral, indigo carmine solution to identify a basic and methyl orange to identify an acid.  I chose bromothymol blue because when it is placed into a neutral solution it turns green which would be easy to identify. Whereas for example blue or red litmus paper only turn from blue to red when something is basic or acidic; they are too general. I chose Indigo carmine because it turns green when something has a ph range of 11.2-13 therefore it would help me easily identify when something is basic.  And lastly I chose methyl orange because it turns red when put in contact with an acid with a range of anything below ph 3.2 therefore it would be easy for me to identify an acid. 

3. When litmus paper turns blue it means that a solution is basic and if the litmus paper turns red it means that the solution is acidic.  Since vinegar is an acid then the extracted lichen would turn red. 

4. The pH indicator bromothymol blue is yellow when a solution is basic being below the ph of 6 (acidic) and is blue when it is above a ph of 7.6 ( basic). Salt water is basic with a ph of 4.5-8.4  (generally) therefore the colour of bromothymol blue would be blue. 

5. 

If I look at the chart provided in the textbook I can conclude that:

a) The region of the world's oceans appear to be the most affected by the drop in pH level are the north Atlantic ocean near Greenland in between North America and  Europe and the South Atlantic ocean by Antartica.

b) The region of the world's oceans appear to be least affected by the drop in pH is in the gulf of Mexico and Australia (by Indonesia). 

Conclusion

         After finishing this lab I concluded that solution A and C were acids and that solution B and D were basic. The most acidic solution was solution A and the most basic solution was solution B. If I do this lab a second time to be more accurate with my results I can use more ph indicators such as phenolpthalein or methyl red. Also to imporve I should be more precise making sure to put the EXACT same amount of each solution and each of the ph indicators to ensure more accurate results.