Increasing The Conversion And Yield Of Chemical Reactions Biology Essay


Increasing the rate, conversion and yield of a chemical reaction is very important in the industry because the ultimate aim of those in the industry would be that of to earn money from this whole process. If the reaction is slow that would directly affect the production of that particular business which would indirectly affect how much can be earn out of this chemical reaction. And due to the bare fact that if the conversion of the product is increased, the amount of yield you would be able to get will increase proportionally alongside the two factors. If the reactant used in this reaction is particularly expensive and the conversion from the reactant to product is little that would cause a great lost to the company. Material balances (mass balances) are based on the fundamental "law of conservation of mass (not volume, not moles)". In particular, chemical engineers are concerned with doing mass balances around chemical processes. So that we are able to make analysis of the situation. And in our experiment the concentrations of the product is changing and henceforth I can see that this process is in an unsteady state. Factors affecting the rate, conversion and yield would can be explained more simply in terms of chemical kinetics where various factors affecting the rate of reaction is discussed in this topic which says that if various thing were done or things were added In the process an increase in rate of reaction can be achieved. The increase of concentration, temperature, the physical state of the reactant which would affect how well the reactants will mix and then how well the reactant reacts together and also the use of a catalyst would also indefinitely increase the rate of reaction. The increase of yield can also be explained by that if the concentration of the reactant is increased, the equilibrium of the reaction would then be disturbed and in order to return to equilibrium, the whole system would try to do something so as to get back its equilibrium, in this case the system would shift the reactions to the product side and hence resulting in an increase in yield. (Singapore Polytechnic, 2009) ( accessed on 1 Jan 2010)

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1.2 Aim

The objective of this experiment is to conduct the saponification of ethyl acetate solution with sodium hydroxide solution so as to determine the principles of material balance for batch reactions, and to observe if certain factors such as yield, conversion and its conductivity rate and would affect the experimental results. Another aim is to determine the relationship between various factors that might interfere with the objective results. (Singapore polytechnic, 2009)

1.3 Hypothesis

The Hypothesis of the experiment is that there would be two different concentration of ethyl acetate at 0.98ml and 0.49ml where one is higher than the other, and that if the rate of reaction and conversion would be higher at the reaction which has a higher concentration or otherwise. This can be seen as the conductivity values can be converted to the concentration of sodium hydroxide in the reacting mixture and if one of the conductivity values is decrease faster than the other we are then able to determine that whether the higher or lower concentration will have a higher rate of reaction and conversion and yield. (Singapore Polytechnic, 2009)

2. Theory

2.1 Saponification

Firstly, the term saponification originated when people started making soap in the olden days. Where the animal fats were then heated alongside a potassium hydroxide solution obtained by leaching wood ashes which contains potash (potassium carbonate) with slaked lime (calcium hydroxide) solution. The term is now commonly used to identify the general process of reacting esters with bases. To put it in simpler terms it simply means the hydrolysis of ester under basic conditions. In our experiment ethyl acetate (ester) and sodium hydroxide (base) will be reacted to produce the desired product of sodium acetate salt and an alcohol. The mechanism of the saponification reaction is placed below . ( accessed on 1 Jan 2010)

Figure 1: Mechanism of Saponification

Following that we will be able to see that we have to study the rate of the reaction of ethyl acetate with base to give the acetate ion and ethyl alcohol. Given the general equation below (figure 2)

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But for the case of our experiment our specific equation would be.


Sodium Ethyl Alcohol Sodium

Hydroxide Acetate Acetate


( accessed on 1 Jan 2010)

2.2 Batch reactions

Secondly, in a batch reaction process, a fix amount of raw material in our case which is ethyl acetate and sodium hydroxide is introduced and the products which is sodium acetate salt and ethanol will be withdrawn before the whole process takes place again. The reactions only produces a fix amount of product from the raw materials fed into the reactions each time the reaction takes place. The whole reaction works in such a way that, firstly, we will have to react the ethyl acetate and sodium hydroxide and measure the amount if acetate ions in the reacting mixture at fix intervals. After that the reaction would have to be stopped and the apparatus would have to be cleaned with deionized water before the reaction with a different concentration of ethyl acetate undergoes the same reaction, so that the results can be used for evaluation. (Singapore Polytechnic, 2009)

2.3 Conversion

Thirdly, conversion is the amount of key reactant that will be transformed from the reactant to product. (Singapore polytechnic, 2009)

We would be manipulating the concentration of ethyl acetate, I can explain how an increase in the concentration of the reactant would cause the conversion to increase and in turn increase the yield of the product too.

I can explain it by Le Chatelier's principle

By Le Chatelier's principle when the concentration of the reactant which is ethyl acetate solution the system will then oppose the change and shift its reaction to the right so as to increase the product which is the sodium acetate salt. This means that the conversion and yield will increase.


Equilibrium will shift to the right, product's side.

Increase concentration

That means that we would most likely have to test this theory with a solution with a lower concentration and a higher concentration.

That also means that if there are two concentrations of these solutions we would have to take down two sets of data for each of the concentration

individually. So that we will be able to find out if there is a difference in concentration would cause the conversion and yield to increase or decrease alongside the factor.

2.4 Yield

Fourthly, a chemical reaction begins by identification of compounds that are called reactants. Various reaction types can be applied to these to come up with the product, or an intermediate product. This requires mixing the compounds in a reaction vessel such as a chemical reactor or a simple round-bottom flask. Many reactions needs some form of agitation before the reaction is started and some form of procedure before the final product is isolate. The amount of product in a chemical synthesis is the reaction yield. In chemistry, yield, also referred to as chemical yield and reaction yield, is the amount of product that can be obtained in a chemical reaction. The absolute yield can be given as the weight in grams or in moles (molar yield). The fractional yield or relative yield or Percentage yield, which serve to measure the effectiveness of a synthetic procedure

The yield follows the following formula:

Moles of key product formed/ Moles of key product fed

In this reaction, the key product formed is sodium acetate (Ch3COONa) and the key reactant is the ethyl acetate (CH3COOC2H5) solution

2.5 Rate of Reaction

There are a few factors that might affect the rate of reaction

Concentration of reactant

If there is an increase in the concentrations of the ethyl acetate, there are more particles per unit volume. Thus the particles are closer to each other and the frequency of collision increases. Resulting in an increase rate of reaction.

Figure 2: Molecules in collision theory

Physical state of reactant

Besides that we also saw that both the physical states of the reactant were liquid and hence forth reactant molecules will mix to collide. When reactants are in the same phase, which was that of the case in our experiment, as in the thermal motion brings them into contact. When they are in different phases, contact occurs only at the at the interface, so vigorous stirring and grinding may be needed which was also another factor that was noticed in our experiment. The more finely divided solid or liquid reactant, the greater the surface area per unit volume, the more contact it makes with other reactants and the faster the reaction will occur.

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Temperature which the reaction occurs, reactant molecule must collide with enough energy to react. Temperature affects the kinetic energy of the molecules and thus the energy of the collision, At a higher temperature, more collision occur in a given time and hence the rate of reaction will be faster. Another factor that could be taken to speed up the rate of reaction.

( accessed on 1 Jan 2010) (Singapore polytechnic, 2009)


A catalyst lowers the activation energy of the reaction. A catalyst is recovered unchanged in a reaction and it does not appear in the product. The particles of the catalyst somehow affect the collision of the reactant particles, usually by providing a site for collision to occur. Thus it is said that a catalyst provides an alternative route of reaction. ( accessed on 1 Jan 2010)

Figure 3: Graph of activation energy difference

Difference between the required amount of activation energy between a reaction that has no catalyst to one that has.

2.6 Conductivity

Conductivity is the measurement of ions in a solution. In our case it is the measurement of sodium hydroxide ions in the solution. And for the measurement of the conductivity of a solution conductivity probe was used. Henceforth I am going to look into how a conductivity probe works.

The Vernier Conductivity Probe can be used to measure either solution conductivity or total ion concentration of aqueous samples being investigated in the field or in the laboratory. It can be connected to any of the Vernier interfaces (ULI, Serial Box Interface, MPLI, or Voltage Input Unit), as well as the Texas Instruments CBL System. Conductivity is now one of the easiest environmental tests of aquatic samples to find out if a kind of water from a place is portable or not. Even though it does not tell you specific ions that are present, it does quickly determine the total concentration of ions in a sample. It can be used to perform a wide variety of tests or planned experiments to determine the changes in or levels of total dissolved ions or salinity: ( accessed on 1 Jan 2009)

How the Conductivity Probe Works

The Conductivity Probe measures the ability of a solution to conduct an electric current between two electrodes. In solution, the current flows because of ion transport. Therefore, an increasing concentration of ions in the solution will result in higher conductivity values as the ions get transferred faster .

The Conductivity Probe is actually measuring conductance, defined as the reciprocal of resistance. When resistance is measured in ohms, conductance is measured and uantified by its SI unit, siemens (formerly known as a mho). Since the siemens is a very large unit, aqueous samples are usually measured in micro siemens, or uS.

Figure 4: Conductivity probe

3. Procedure

A. Preparation of chemicals

3.1 The MSDS of sodium hydroxide and ethyl acetate was read through. The disposal and handling of the chemicals were also familiarized. Disposable gloves and chemical goggles were also worn when the chemical was used.

3.2 Then 500 ml of 0.01M sodium hydroxide and 500ml of ethyl acetate solution was prepared to the required concentration of the experiment. Suggestion: 2 flasks of sodium hydroxide and ethyl acetate solutions were prepared. The first experiment was performed and the flasks were cleaned before the other 2 flasks of the second experiment were prepared. Following that 500ml of 0.01M sodium hydroxide solution was prepared. After that the required volume of 0.1M NaOH stock solution was measured using a measuring cylinder. The solution was then poured into a 500ml volumetric flask. And then the volumetric flask was then filled with de-ionized waster to the 500ml mark. The flask was then covered, shook and inverted.500ml of ethyl acetate solution was then prepared (The ethyl acetate was prepared in a fume hood at W314). 250ml of de-ionized water was poured into a 500ml volumetric flask. And then the required volume of ethyl acetate stock solution was measured

out using a micro-pipettor. And then the solution was dispensed into a 500ml volumetric flask. The volumetric flask was then filled with de-ionized water till the 500ml mark. The flask was then covered, shook and inverted.

B. Experimental setup

Figure 2 was referred to for the experimental setup

Figure 5: Experimental setup

The experiment was pieced together and then the permission to run the experiment was obtained.

C. Procedure

3.3 The prepared sodium hydroxide was poured into a reactor. The reaction conditions were adjusted to the predetermined levels. The reaction conditions such as temperature, stirring speed, concentrations and volumes of the reactants were recorded. The conductivity meter probe was then positioned into the reacting mixture. Following that the ethyl acetate was then poured into the reactor and then the timer was started immediately. The conductivity values were recorded at a interval of 1 minute for 30 minutes of reaction time. The stirring device and magnetic stir bar was removed by a magnetic bar after 30 minutes of reaction time. The conductivity probe was removed and rinsed thoroughly using de-ionized water. The reaction product was then disposed into a plastic waste container. The glass ware was then rinsed and the experiment was repeated. The conductivity probe was then removed from the reacting mixture at the end of the experiment with de-ionized water. And then all the chemicals was disposed into the plastic waste container and the unused reactants was then brought to W314 for proper treatment and disposal. The used glass ware was then rinsed and the work space was tidied up.

4. Results and Calculation

4.1 Tabulate the experimental result showing the conductivity values (µS/cm) and concentration of NaOH for each of the reaction conditions studied.

Table 1: Conductivity values and concentration and NaOH for 0.49ml concentration

Table 2: Conductivity values and concentration and NaOH for 0.98ml concentration

Figure 6: Calibration Chart of conductivity probe

4.2 Plot a graph of concentration of NaOH (M) against reaction time (min) for each of the reaction conditions studied.

Data set 1

Figure 7: Graph of concentration versus reaction time for 0.49ml

Data set 2

Figure 8: Graph of concentration versus reaction time for 0.98ml

4.3 From each of the graphs, determine the conversions of NaOH and yield of sodium acetate per mole of NaOH fed after 15 minutes of reaction.

From Data set 1

At 15 minutes, concentration of NaOH = 0.00097 M

Percentage conversion of NaOH = Moles of NaOH reacted x 100%

Moles of NaOH fed into reactor

Moles of NaOH fed into reactor = 0.01 M x 0.5 L

= 0.005 moles

Moles of NaOH reacted = 0.005 M - ( 0.00097 M x 1 L )

= 0.00403 moles

Percentage Conversion = 0.00403 x 100 %


= 80.6 %

From Data set 2

At 15 minutes, concentration of NaOH = 0.00068 M

Percentage conversion of NaOH = Moles of NaOH reacted x 100%

Moles of NaOH fed into reactor

Moles of NaOH fed into reactor = 0.01 M x 0.5 L

= 0.005 moles

Moles of NaOH reacted = 0.005 M - ( 0.00068 M x 1 L )

= 0.00432 moles

Percentage Conversion = 0.00432 x 100 %


= 86.4 %

Yield of a product

Moles of sodium acetate formed

Moles of NaOH fed into reactor

Therefore mole ratio of NaOH and CH3COONa is 1 : 1

Data sheet 1

Moles of sodium acetate = 0.00403 moles

Yield = 0.00403


= 0.806

Data sheet 2

Moles of sodium acetate = 0.00432 moles

Yield = 0.00432


= 0.864

4.4 Determine the rate of reaction equation for each of the reaction conditions by using material balance equation for a batch reaction.

Data sheet 1

Graph of vs. CA

Figure 9: Graph of concentration versus rate of reaction for 0.49ml

Data sheet 2

Figure 10: Graph of concentration versus rate of reaction for 0.98ml


The graph will be a curve.

Gradient =

Data set 1

Gradient = 20.329

Data set 2

Gradient = 53.444

5. Discussion

5.1 Factors affecting rate of reaction

There are two concentration of the ethyl acetate used in our experiment where one is higher at 0.98ml and the other one is lower at 0.49ml. And between this two concentrations there will be effects of the increase of concentration that would cause the rate of reaction of the saponification reaction to increase. And as we can see from the comparison of table 1 and table 2 which are the results of our experiment we can see that the concentration of sodium hydroxide is decreasing more rapidly for the reaction that has 0.98ml of ethyl acetate than the other one. This would simply means that the higher the concentration of the reactant the faster the reaction. And that is solely because when the concentration of the ethyl acetate the amount of ethyl acetate molecules per unit area is higher than that of the 0.98ml to that of the 0.48ml and as more molecules are found closer together, that would increase the chance of collisions. Hence increasing the rate of reaction.

5.2 Factors affecting conversion and yield

Factors that affect conversion is also concentration as if there is higher concentration the more ethyl acetate molecules will be found per unit area and hence there were be more effective collisions. Resulting in more reactant being converted into products and that would mean that there is an increase in both conversion and yield with the increase of concentration. And for yield the increase in yield can also be explained in the terms of equilibrium of system where an increase of the concentration of the reactants would upset the equilibrium of the system and then, and then to oppose the change in the system the system will then push the equilibrium to the products side, resulting in more products being formed and that would definitely increase the yield.

5.3 Factors affecting the conductivity value

The conductivity is the measurement of the sodium hydroxide ions in the reacting mixture, as the ions of the other reactants or products is negligible. And from the results obtained from the experiment you all can see that the amount of sodium hydroxide ions decreases with time because as the sodium hydroxide is used up in the reaction, hence explain the depletion of the sodium hydroxide ions. For the results of the reaction using the 0.98ml the decrease in the sodium hydroxide ions is faster than that of the 0.49ml as the higher the concentration the faster the sodium hydroxide will be converted into the products.

5.4 Precautions taken in the experiment

Precautions such as preparing the ethyl acetate in the fume hood, wearing gloves when working on the experiment and wearing goggles were carried out throughout the experiment. Firstly, we had to prepare the ethyl acetate solution in the fume hood because the ethyl acetate will vaporize and these vapors are toxic, therefore we had to prepare the solution in the fume hood. Secondly, we had to wear gloves throughout the experiment because sodium hydroxide is rather corrosive and when carrying out the experiment, there might be accidental spills on our hands. Therefore if we wear glove our hands will be protected and the damage of the corrosive sodium hydroxide will be minimized. Lastly, we had to wear goggles as the reacting mixture might get into our eyes when carrying out the experiment; therefore we had to wear the goggles.

5.5 Comparison of the rate of reaction between 0.98ml and 0.49ml ethyl acetate reaction

As we can see from table 1 and table 2 the conductivity values which is the concentration of sodium hydroxide ions in the solution decrease faster in table2 compared to table 1. We can also see that with the plotted graph figure 7 and 8, figure 8 has a steeper gradient compared to figure 7. This also means that the reaction with 0.98ml of ethyl acetate has a faster rate of reaction. As more molecules are found per unit area and then the molecules are nearer to each other, therefore the time taken for each collision is faster.

5.6 Comparison of yield between both concentrations

The yield calculated for both experiment is 0.806 and 0.864 for the reaction with 0.49ml and 0.98 respectively. That would means that the reaction with 0.98ml ethyl acetate has higher yield than that of the reaction with 0.49ml ethyl acetate. With the increase in concentration the amount of ethyl acetate molecules will increase, hence increasing the chance of effective collisions too. And the more reactant will be converted from reactant to products. In the presences of a catalyst the amount of yield would not increase, as the catalyst will only increase the rate of reaction and nothing else.