Chemistry 11 – Acid Base Inquiry Lab

Acid Base Titration Lab 

The purpose of the lab was to find the concentration and identify the unknown base with only the given solid acid: Oxalic Acid (C2H2O4) 

List of materials 

• Oxalic Acid (C2H2O4) 
• Unknown Base  
• Pipette 
• burette 
• 100 ml beaker x 2 
• Phenolphthalein dropper 
• Stand and burette clamp 

Procedure 

1. Ensure that both 100mL beakers are clean and dry and label one “Acid” and one “Base”. 
2. Put 0.045 g of solid acid in the 100mL beaker labeled “Acid”, then dilute to 100mL with water 
3. To prepare the burette, pour 5mL from the beaker labeled “Acid” into the burette. Hold the burette almost horizontally and roll it to coat the inside of the burette with the solution. Pour the remaining acid down the sink and do that process one more time. The burette is now considered clean.   
4. Carefully pour in an adequate amount of your acid into the burette to fill it about 2cm above the “0” mL mark. Hold the burette firmly over the sink, quickly open the stopcock and re-close it while simultaneously giving a downwards jerk to remove any air bubbles. Drain out the remaining acid until it reaches the “0” mL mark. Record the initial burette volume in your table. 
5. Prepare the pipette in a similar way as the burette. Instead of putting 5mL of acid, you will put 2mL of the base and coat the inside twice. Once the pipette clean use pipette to put 10mL of the Unknown Base into 100mL beaker labeled “Base”. 
6. add 2-3 drops of phenolphthalein into the 100mL beaker labeled “Base”, the solution will turn a hot pink. 
7. slowly add the acid to the base until it becomes clear, when it does, record the amount of base used in your table. Repeat the titration two more times and record your results as you go. 

 

Data Table:

Molarity of	Trial 1	Trial 2	Trial 3
Initial Reading of burette (mL)	0 mL	12.23 mL	25.34 mL
Final reading burette (mL)	12.23 mL	25.34 mL	36.88 mL
Volume of HOOCOOH used (mL)	12.23 mL	13.11 mL	11.54 mL
Average volume of HOOCCOOH (mL)	12.29 mL

 

 

Calculate moles of HOOCCOOH, then calculate Concentration:  

0.01 L x 0.05M = 0.0005 mol of HOOCCOOH       

 

Calculate moles of Base, then concentration   

5×10(-4) mol HOOCCOOH x 1/1 = 5×10(-4) mol Ca(OH)2   

0.0005mol base / 0.01 L base = 0.05 M of Ca(OH)2 

 

Base Flame Test 

The purpose of the flame test is to determine an unknown acid or base based on what color it changes the flame color to, which you then compare to a chart for your result’s closest match. 

List of materials 

• Unknown Base solution 
• 100mL beaker 
• Tweezers 
• Q-tip(s) 
• Bunsen Burner 

Procedure 

1. Pour approximately 10mL of your unknown base solution into your 100mL beaker 
2. Ignite the Bunsen burner (Make sure long hair is tied back, and safety goggles are on) 
3. With a pair of tweezers, grab the cotton swap by one end, and dip the other end into the 100mL beaker of your unknown base solution 
4. Carefully place the end of the cotton swab with the unknown base solution into the flame. It may take a couple attempts 
5. Observe flame color and match it according to the Flame Test Color Chart 

 While doing the flame test, the flame turned from blue to an orange color. We did the procedure a couple times to be certain, but we finally agreed that the flame turned orange. We checked the chart and established that the Unknown base is Calcium Hydroxide. 

 

Conclusion

Our lab results concluded that the Unknown Base’s identity was Calcium Hydroxide (Ca(OH)2). As a group be decided to revert to some of our previous lab experiments and found the lab that most fit our situation and needs was the titration lab we did on May 11th, 2023. The lab would assist us in finding the concentration of the given acid (C2H2O4). Once we had the concentration, we could multiply it by the litres used to find the moles. We did extensive research on what we could do to determine the identity of our Unknown Base, and in the process, we came across the Flame Test. The lab helped our group figure out that the Unknown Base was Calcium Hydroxide (Ca(OH)2). The beakers or cotton swabs could have been dirty. If they had any remnants of previous lab chemicals, it would alter the results of our experiment. The cotton swabs could’ve had some sort of chemical residue from their original assembly process. Either of these could have affected either of our experiments and altered the results from our labs. We could use the same process for the beakers that we did for the burette or pipette. We could also thoroughly rinse out the beakers to ensure any chemical residue is washed away before our lab. For the cotton swabs, we could use distilled water to “purify” them to make sure there is nothing in them that could interfere with the lab.