LAB 5-1B: Properties of Acids and Bases

Purpose:

• The purpose of this lab was to determine how the properties of acids and bases can be used to classify solutions and to investigate the acid-base properties of four unknown solutions.

Materials:     

•   4x6 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

Procedure:

•   Refer to text, page 230

Results:

Mg Ribbon	Red Litmus	Blue Litmus	Bromothymol Blue	Indigo Carmine	Methyl Orange	Unknown
Bubbles	Pink	Pink	Yellow	Dark Blue	Red	A
No change	Blue	Light Blue	Blue	Green	Orange	B
Little bubbles	Pink	Light Blue	Turquoise	Dark Blue	Orange	C
No change	Red turned in to Blue	Blue	Blue	Dark Blue	Orange	D

Picture of results

Materials & Substances:

Left column to right column:

Mg ribbon – Bromothymol Blue
– Red Litmus – Blue Litmus – Indigo Carmine – Methyl Orange

Top row to bottom row:

Solution A – Solution B – Solution C – Solution D

Discussion:

Analyze

1. List the solutions in order from most acidic to least acidic (mostbasic).

• The solutions in order from most acidic to least acidic(most basic) are A, C, D, B.

2. Which solution do you think was neutral? Explain how you know.

• I think if there was indeed a solution that was neutral it would be Solution D because there were no bubbles in the solution with magnesium ribbon and both of the litmus paper color's changed the least out of all 4 solutions.

3. You used two bases. Explain how you know which solution was more alkaline(more basic).

• I know thatsolution B was more alkaline (more basic) than solution D because all the colorchanges were more extreme, especially the red litmus; it turned more bluecompared to solution D.

4. How can magnesium metal be used to distinguish between an acid and abase?

• Magnesium metal can be used to distinguish between anacid and a base because when you put it with an acid it produces hydrogen gas,which will produce visible bubbles in the solution.

Conclude and Apply

1.

(a) What color would each of the five indicators be in a solution thatis pH 3?

•     Red litmus – Red
•     Blue litmus – Pink
•     Bromothymol blue – Yellow
•     Indigo carmine – Dark blue
•     Methyl orange - Red

(b) What color would each of the five indicators be in a solution thatis pH 10?

•     Red litmus - Blue
•     Blue litmus – Blue
•     Bromothymol blue – Dark blue
•     Indigo carmine –  Green - Yellow
•     Methyl orange – Bright orange - yellow

2. Suppose you are asked to put together a test kit to determine whetherwater taken from a factory waste drain is acidic, basic, or neutral. Your kitcan contain only three tests. Which tests would your kit contain? Explain.

• If I could only have 3 tests I would put together atest kit containing Methyl orange, red litmus paper and Bromothymol blue. Thered litmus paper will clearly determine whether the solution is an acid or abase, if the result is closer towards the middle of the spectrum Bromothymolblue will narrow it down and determine if the water is slightly acidic or alittle more basic and Methyl orange will also help specify the pH level of thesolution towards the corrosive end and give a greater understanding andconfirmation.

3. Refer to the photo of the lichen Roccella tinctoria on this page,from which litmus is extracted. If this lichen were ground up and then soakedin vinegar, what color would the solution likely be? 

• If Roccella tinctoria was soaked in vinegar the solution would most likely be the color red because vinegar is acidic therefore it would have a low pH and be towards the red side of the spectrum. 

4. What is the color of seawater that has had Bromothymolblue added to it?

• The color of seawater with added Bromothymol bluewould be blue or towards the blue end of the spectrum because seawater is basic.

5. Consider the color-coded map of the world’s oceans shown to theright.

(a) Which regions of the world’s oceans appear to be most affected bythe drop in pH level?

• The regions of the world’s oceans that appear to bemost affected by the drop in pH levels are close to the poles of the earth, thenorth Atlantic towards Antarctica and the South Atlantic around the Arctic area.

 (b) Which regions are the leastaffected?

• The regions of the world that appear to be the leastaffected by the drop in pH level are the south side of the Pacific Ocean and asmaller region in the Indian Ocean.

Conclusion:

• Through this experiment I have gained a much greater understandingin how acids and bases react to different solutions, how we can use acids andbases to classify solutions and how much the pH level affects compounds andmany things around us. Through the clumsy solution pouring process thesubstances may have gotten contaminated, this is a factor that should be donemore carefully next time, possibly because of that factor some of the solutionswere hard to analyze therefore it was beneficial that we had various kinds ofindicators to confirm whether our observation of it being an acid or a base wasindeed correct. Another thing we could have done to improve our results is tosand our Magnesium ribbon to remove more oxides so that the bubbles are moreobvious to the eye.