Determination of the Percent Yield of Sodium Acetate When a Chemical Reaction with Sodium Bicarbonate Occurs

Determination of The Percent Yield of Sodium Acetate When a Chemical Reaction with Sodium Bicarbonate Occurs

1. Design

1. Introduction

1. The purpose of this lab is to determine the percent yield of a chemical reaction between sodium bicarbonate (baking soda) and acetic acid (vinegar). When the two products reacted together, a double replacement occurred. This then changed to dihydrogen monoxide, carbon dioxide, and sodium bicarbonate, otherwise known as the products.  One way that we purified the sodium acetate was by boiling away the water.  Another way we could have purified it is by filtration; this process works by getting a “cloth or a membrane” so that it allows the liquids to facilitate through.  And since this is a balanced chemical equation, it’s easy to find the percent yield. To find the percent yield, you use three conversion factors for each reactant to change to the product that you want; in this case, we are looking for the percent yield of sodium acetate. In the first step, you covert the mass of one of the reactants to moles using molar mass.  Next, you use the mole to mole ratio to convert to sodium acetate.  Then, you change to grams using molar mass again. After you have done these steps for both reactants, you compare the two numbers. Whichever number is smaller is the theoretical yield.  The limiting reagent is the reactant at was associated with the theoretical yield and the other reactant is excess.  Finally, you take how much sodium acetate was made and divide that number by the theoretical yield and multiply by 100.  This gives you the percent yield and according to the law of conservation of mass, we can expect our percent yield to be less than 100 percent, for “matter cannot be created or destroyed”.  Supported by this statement, our percent cannot be a negative number either.  This is how we can determine if a percent yield is correct or incorrect.    https://en.wikipedia.org/wiki/List_of_purification_methods_in_chemistry     http://chemistry.about.com/od/chemistryglossary/a/conservmassdef.htm   

1. Research Question

1. What is the percent yield of sodium acetate in a chemical reaction between sodium bicarbonate and acetic acid.  

1. Variables

1. Independent – sodium bicarbonate

2. Dependent - sodium acetate

3. Control Group - none

1. Materials

1. 500mL Erlenmeyer Flask (+/- 0.1)

2. Baking Soda

3. Vinegar

4. Wire Gauze

5. Hot Plate (+/- 0.01)

6. 50 mL Graduated Cylinder (+/- 0.1)

7. Goggles

8. Paper Towels

9. Beaker

10. Calculator

1. Procedure

1. Electrical balance was turned on and set to zero.  

2. The mass of an empty 500 mL Erlenmeyer flask was measured on the balance.  

3. The prescribed amount of sodium bicarbonate was measured.

4. The sodium bicarbonate was added to the flask while it was still on the balance.  

5. 50.0 mL of acetic acid was poured in a graduated cylinder.  

6. 50.0 mL of acetic acid was poured into the Erlenmeyer flask and stirred for two minutes.  

7. The hot plate was turned on.  

8. After the reaction settled, the flask was placed on the hot plate.  

9. When there was no more water in the flask, a rolled sheet of paper towel was used to move the flask onto the wire gauze to cool down.  

10. After the flask cooled down, it was put onto the balance to measure the mass.  

11. Finally, the percent yield was calculated  

1. Data Processing and Presentation

1. Data Collection  

1. Mass of Sodium Bicarbonate

1. Theoretical Yield calculation

1. Qualitative data – The reactants like the vinegar was a clear liquid with tiny bubbles and the baking soda was a white powder.  At the beginning, the reaction was bubbling and then a gas cloud was released. Then the bubbling came back until it settled. When the flask was on the hot plate, condensation was forming at the top and the white liquid started to get thicker. Finally, all the water was evaporated and only the white powder, sodium acetate, was left.

2. Errors -  

1. There was a tiny bit of moisture in the flask after it was measured for the actual yield, this could have changed the percent yield and cause a miscalculation.  

2. When we measured the volume of the vinegar in the graduated cylinder, we didn’t check to see if the bottom of the meniscus was right at the line. This could have also altered the percent yield and the rest of the products.

3. When we put the baking soda in the flask, a little bit got outside the flask, this could alter the reaction’s products which would also alter the percent yield.

1. Data Processing and Presentation

1. Percent Yield Calculation

1. Conclusion and Evaluation

1. Conclusion

1. The relationship between sodium acetate and sodium bicarbonate is, as the sodium bicarbonate increases, the sodium acetate increases. This is because the sodium bicarbonate is a reactant and if you change a value in this part of the equation, you change the values in the products’ sections. For example, we used 4.04 grams of baking soda and that resulted in making 3.86 grams of sodium acetate. If we increased the value of the baking soda, the value of the acetate would increase, but if you were to do the experiment perfect every time, the percent yield would be the same in every trial. The reason it would stay the same was because the sodium acetate and sodium bicarbonate are related in a proportion meaning that if one changes, the other one changes or the other one changed and the ratio would be the same.

1. Evaluation

1. Limitation – the lab was only one trial and it didn’t show us how it could have been in many trials. This could be fixed by adding more trials to the experiment and having us compare the percent yields

2. Limitation – we could have also used different masses of sodium bicarbonate. This would give us a broader aspect of how the percent yield can change with different masses of baking soda. One way to fix this limitation could be my doing separate trials of 0.05 mol, 0.1 mol and 0.15 mol of baking soda.

3. Weakness – one weakness in this reaction was when some of the baking soda was split and didn’t make it into the flask. This could have changed the reaction’s product causing the percent yield to be false.

4. Weakness – another weakness was when we measured the volume of vinegar and we didn’t check to see if the bottom of the meniscus was at the 50-mL line. This could have also altered the products because in the calculation for the theoretical yield, we used a certain amount of each reactant and the percent yield wouldn’t be the same.