Skills and Applications Task: Topic Test · 2018-08-28 · Brianna Lush (a1667331) Chemistry Curriculum and Methodology A Term 1, 2017 STAGE 2 CHEMISTRY Skills and Applications Task:

Brianna Lush (a1667331)

Chemistry Curriculum and Methodology A

Term 1, 2017

STAGE 2 CHEMISTRY

Skills and Applications Task: Topic Test

Organic and Biological Chemistry Part 2 – Esters, Amides, Triglycerides and Proteins

Time Duration: 5 minutes reading time + 55 minutes writing time

Total marks: 50 marks

Name: _________________________ Student Number: ____________________

Performance Standards Assessed:

KA1 Demonstration of knowledge and understanding of chemical concepts.

KA2 Development and application of chemical concepts in new and familiar contexts.

KA3 Exploration and understanding of the interaction between science and society.

KA4 Communication of knowledge and understanding of chemical concepts and information, using

appropriate terms, conventions and representations.

IAE3 Analysis and interpretation of data and other evidence to formulate and justify conclusions

STAGE 2 CHEMISTRY – Organic and Biological Chemistry Topic Test

Part 2: ESTERS, AMIDES, TRIGLYCERIDES AND PROTEINS

QUESTION 1

a) Pineapples contain a wide variety of organic compounds.

One of the esters that contribute to the aroma of pineapple is shown below.

i) State the systematic name of the ester.

(2 marks) [KA1]

b) Esters are prepared in a reaction of a carboxylic acid with an alcohol to produce two

products – the ester and water.

i) State the name given to this type of reaction.

(1 mark) [KA1]

ii) Draw and clearly label the structures of the carboxylic acid and the alcohol from which

this ester could be prepared.

(2 marks) [KA1]



iii) Explain why it is necessary to prepare esters under reflux conditions.

(3 marks) [KA4]

iv) Write an equation for the hydrolysis of the ester under alkaline conditions.

(2 marks) [KA2]

[Question 1 Total – 10 marks]



QUESTION 2

Triolein is a triglyceride found in canola oil that is produced in a reaction of propane-1,2,3-triol

with oleic acid. The structure of oleic acid is given below.

Oleic acid

a) State whether oleic acid is a saturated or unsaturated fatty acid.

(1 mark) [KA1]

b) Draw the structural formula of triolein.

(1 mark) [KA1]

c) Canola oil can be converted to margarine through a hydrogenation process.

i) Explain how hydrogenation allows liquid oils to be converted into solid fats.

(2 marks) [KA1]



ii) Write an equation for the hydrogenation of oleic acid.

(2 marks) [KA2]

iii) Describe one factor that causes the rate of hydrogenation reaction to increase.

(2 marks) [KA4]

d) Canola oil can also be used to make cleaning agents such as detergents by undergoing

saponification (alkaline hydrolysis). During saponification, triglycerides are hydrolysed to

form carboxylate ions and propane-1,2,3-triol.

i) State the reactants and conditions required for saponification to occur.

(1 mark) [KA1]

ii) Carboxylate ions are said to be amphipathic molecules. Define amphipathic.

(1 mark) [KA1]



iii) Explain how the production of carboxylate ions allows dirt and grease to be removed

when cleaning due to the formation of micelles.

(4 marks) [KA4]

e) Some students conducted an experiment to determine the bromine numbers of 5 unknown

triglyceride solutions. A standard solution of bromine in cyclohexane was added from a

burette to a known volume of a standard solution of the triglyceride solution. The end point

of the experiment was indicated by the first sign of permanent orange colour in the titration

flask. The data from the experiment is given in the table below.

Triglyceride Solution Bromine Number

V 92

W 11

X 163

Y 84

Z 132

i) State, with reasoning, which triglyceride solution has the highest degree of saturation.

(2 marks) [IAE3]



ii) In the experiment report, one student concluded that triglyceride solution X had the

highest melting point and therefore was a solid at room temperature. Explain, with

reasoning, if the student’s conclusion was correct or incorrect based on the data.

(4 marks) [IAE3]




QUESTION 3

Wool is a natural material that is composed of proteins. Arginine and Glycine are two amino acids

that make up polypeptide chains in wool and the structures of these two amino acids are shown

below.

Arginine

Glycine

a) Explain how the structure of these amino acids allows them to be classified as α-animo acids.

(2 marks) [KA1]

b) Write an equation for the condensation reaction between Arginine and Glycine.

(2 marks) [KA2]

c) Wool is a very good material for readily absorbing water. Explain the interactions which

allow this to occur.

(2 marks) [KA2]



d) In all organisms, chemical reactions are continuously occurring because they are vital for

survival. Often these reactions are facilitated by enzymes. In humans, catalase is an enzyme

which catalyses the breakdown of hydrogen peroxide into water and oxygen. This reaction is

important because accumulation of hydrogen peroxide can be toxic and cause cells to

become damaged.

i) Suggest, with reasoning, the optimum temperature for catalase.

(2 marks) [KA2]

ii) When someone is unwell, often one of their symptoms is a fever (high body

temperature). Fever is important in the process of fighting bacterial infection in the

body, however due to the discomfort it causes, many people treat a fever with

paracetamol (pain relief) medication very quickly. Explain how allowing a short-

term fever is actually beneficial for fighting bacterial infection.

(4 marks) [KA3]




QUESTION 4

Molecules involving the amide functional group are commonly found in a range of everyday

materials and products.

a) N,N-diethyl-m-toluamide is the active ingredient in a popular brand of insect repellent. Its

structure is given below.

N,N-Diethyl-m-toluamide

i) Draw and clearly label the carboxylic acid and amine that are used to produce N,N-

Diethyl-m-toluamide.

(2 marks) [KA2]



b) Kevlar is a strong material that is found in body armour and protective clothing. It is made

up of polymer chains that consist of benzene rings joined by amide links. These polymer

chains are formed from a condensation reaction of benzene-1,4-dicarboxylic acid with 1,4-

diaminobenzene. The structures of these monomers are shown below.

Benzene-1,4-dicarboxylic acid 1,4-diaminobenzene

i) Write the equation for a condensation reaction of benzene-1,4-dicarboxylic acid with

1,4-diaminobenzene. Circle the amide link in the final product.

(2 marks) [KA2]



ii) Kevlar polymer chains are arranged parallel to each other. Using a diagram to support

your answer, explain the interactions that occur between polymer chains which

contribute to the strength of Kevlar.

(4 marks) [KA4]


– END OF TEST –



Marks Grid

Question Marks IAE

1

IAE

2

IAE

3

IAE

4 KA1 KA2 KA3 KA4 Difficulty

1a i) 2 x Easy

1b i) 1 x Easy

1b ii) 2 x Easy

1b iii) 3 x Medium/Hard

1b iv) 2 x Easy/Medium

2a 1 x Easy

2b 1 x Easy

2c i) 2 x Medium

2c ii) 2 x Easy/Medium

2c iii) 2 x Medium

2d i) 1 x Easy

2d ii) 1 x Easy

2d iii) 4 x Medium/Hard

2e i) 2 x Medium/Hard

2e ii) 4 x Hard

3a 2 x Easy/Medium

3b 2 x Easy/Medium

3c 2 x Medium

3d i) 2 x Easy/Medium

3d ii) 4 x Hard

4a 2 x Easy

4b i) 2 x Easy/Medium

4b ii) 4 x Hard

TOTAL 50 2 8 8 1 4



SOLUTIONS

QUESTION 1

a) Pineapples contain a wide variety of organic compounds.

One of the esters that contribute to the aroma of pineapple is shown below:

i) State the systematic name of the ester.

Ethyl Propanoate (2 marks) [KA1]

b) Esters are prepared in a reaction of a carboxylic acid with an alcohol to produce two

products – the ester and water.

i) State the name given to this type of reaction.

Condensation Reaction (1 mark) [KA1]

ii) Draw and clearly label the structures of the carboxylic acid and the alcohol from

which this ester could be prepared.

(2 marks) [KA1]



iii) Explain why it is necessary to prepare esters under reflux conditions.

Reflux is a process by which a mixture of the reactants and products is boiled for

a prescribed period of time. The esterification reaction is quite slow, so by heating

the mixture, this allows the rate of reaction to increase. Reflux conditions also

prevents the loss of volatile reactant and product vapours from the reaction vessel.

While the reaction mixture is heating, some of the reactants and products

vapourize and become volatile. As these hot vapours rise up into the condenser,

they are cooled and condense into liquid droplets that fall back into the reaction

mixture. (3 marks) [KA4]

iv) Write an equation for the hydrolysis of the ester under alkaline conditions.

(2 marks) [KA2]


QUESTION 2

Triolein is a triglyceride found in canola oil that is produced in a reaction of propane-1,2,3-triol

with oleic acid. The structure of oleic acid is given below.

Oleic acid

a) State whether oleic acid is a saturated or unsaturated fatty acid.

Unsaturated (1 mark) [KA1]



b) Draw the structural formula of triolein.

(1 mark) [KA1]

c) Canola oil can be converted to margarine through a hydrogenation process.

i) Explain how hydrogenation allows liquid oils to be converted into solid fats.

Hydrogenation involves addition of hydrogen across C=C double bonds. When this

occurs in liquid oils, oil molecules become more saturated (less double bonds). As a

result, the molecules become more ordered and compact, which allows them to be

able to pack very closely together and hence are able to form a solid.

(2 marks) [KA1]

ii) Write an equation for the hydrogenation of oleic acid.

(2 marks) [KA2]

iii) Describe one factor that causes the rate of hydrogenation reaction to increase.

Describe one of the following: Temperature – The rate of reaction is related to the

number of productive collisions between reactant molecules. Increasing temperature



increases the energy of colliding reactant molecules so that more collisions in a given

time lead to the formation of products and hence the reaction rate is faster. OR High

Pressure – increasing the pressure increases the concentration of the gaseous reactant

hydrogen. Hence there will be more collisions between the reactant molecules and

therefore more productive collisions in a given time, resulting in a faster reaction rate.

OR Nickel Catalyst – adding a catalyst provides a new pathway for the reaction with

a lower activation energy. More of the collisions will involve particles with energy

exceeding the activation energy, so there will be more productive collisions in a given

time and hence a faster reaction rate. (2 marks) [KA4]

d) Canola oil can also be used to make cleaning agents such as detergents by undergoing

saponification (alkaline hydrolysis). During saponification, triglycerides are hydrolysed

to form carboxylate ions and propane-1,2,3-triol.

i) State the reactants and conditions required for saponification to occur.

Triglyceride (fat or oil), concentrated sodium hydroxide solution and heat

(1 mark) [KA1]

ii) Carboxylate ions are said to be amphipathic molecules. Define amphipathic.

A molecule which has both hydrophobic and hydrophilic regions

(1 mark) [KA1]

iii) Explain how the production of carboxylate ions allows dirt and grease to be

removed when cleaning due to the formation of micelles.

Substances such as dirt and grease do not dissolve in water because they are non-

polar and water is polar. Carboxylate ions have hydrophobic and hydrophilic

regions. The hydrophobic, non-polar hydrocarbon chain attaches to the non-polar

dirt or grease and the hydrophilic, polar head interacts with the polar water

molecules to create a globule of dirt/grease. With some agitation to the system,

the globule dislodges from the surface it is attached to and the carboxylate ions

come together to form spheres called micelles. The centre of the micelles are

hydrophobic and contain the globules of dirt/grease. Because the ionic heads are

negatively charged, the micelles repel each other which prevents the globules

from joining back together to form larger clumps of insoluble substances. The



interactions between the ionic heads on the micelle and water allow the micelle to

become soluble in water. As a result, when the water is washed away, the micelles

(containing the dirt/grease) are washed away, leaving a clean surface behind.

(4 marks) [KA4]

e) Some students conducted an experiment to determine the bromine numbers of 5

unknown triglyceride solutions. A standard solution of bromine in cyclohexane was

added from a burette to a known volume of a standard solution of the triglyceride

solution. The end point of the experiment was indicated by the first sign of permanent

orange colour in the titration flask. The data from the experiment is given in the table

below.

Triglyceride Solution Bromine Number

V 92

W 11

X 163

Y 84

Z 132

i) State, with reasoning, which triglyceride solution has the highest degree of

saturation.

Triglyceride solution W has the highest degree of saturation. It has the lowest

bromine number, which indicates it has the least number of double bonds of the

triglyceride solutions tested. (2 marks) [IAE3]

ii) In the experiment report, one student concluded that triglyceride solution X would

have the highest melting point and therefore was a solid at room temperature.

Explain, with reasoning, if the student’s conclusion was correct or incorrect based

on the data.

According to the data, the students conclusion was incorrect. Triglyceride solution

X had a bromine number of 163 which suggests that it has the highest degree of

unsaturation of the 5 solutions tested. This means that the structure of the



triglycerides in the solution would be disordered and loose, due to the presence of

the double bonds in the molecules. The triglyceride molecules cannot pack as

tightly together and hence it would be expected that the triglyceride would be

liquid at room temperature. If it is liquid at room temperature, it would be

expected that the melting point would be relatively low.

(4 marks) [IAE3]


QUESTION 3

Wool is a natural material that is composed of proteins. Arginine and Glycine are two amino acids

that make up polypeptide chains in wool and the structures of these two amino acids are shown

below:

Arginine

Glycine

a) Explain how the structure of these amino acids allows them to be classified as α-amino acids.

These amino acids can be classified as α-amino acids because there is a central carbon atom

(called the α-carbon) that is covalenty bonded to a hydrogen atom, anime functional group,

carboxyl functional group and another atom or group of atoms. (2 marks) [KA1]



b) Write an equation for the condensation reaction between Arginine and Glycine.

(2 marks) [KA2]

c) Wool is a very good material for readily absorbing water. Explain the interactions which

allow this to occur.

The polar peptide links in protein chains that make up wool are able to form hydrogen bonds

with water molecules. The oxygen atom on the carbonyl group can form hydrogen bonds

with the hydrogen atoms on the water molecules. Similarly, the hydrogen that is attached to

the nitrogen is able to form hydrogen bonds with the oxygen on the water molecules. Since

the water molecules are attached to the peptide chains, water is absorbed into the material.

(2 marks) [KA2]

d) In all organisms, chemical reactions are continuously occurring because they are vital for

survival. Often these reactions are facilitated by enzymes. In humans, catalase is an enzyme

which catalyses the breakdown of hydrogen peroxide into water and oxygen. This reaction is

important because accumulation of hydrogen peroxide can be toxic and cause cells to

become damaged.

i) Suggest, with reasoning, the optimum temperature for catalase.

The optimum temperature for catalase would be approximately 37°C, as this is the

average body temperature. (2 marks) [KA2]



ii) When someone is unwell, often one of their symptoms is a fever (high body

temperature). Fever is the body’s natural response to fighting infection, however due

to the discomfort it causes, many people treat a fever with paracetamol (pain relief)

medication very quickly. Explain how allowing a short-term fever is actually

beneficial for fighting bacterial infection.

Like humans, bacteria also have enzyme-facilitated chemical reactions occurring

which are vital for their survival, particularly growth and replication. Enzymes are a

type of protein and hence have an optimum temperature at which they function.

During a fever, the temperature of the environment that the bacteria are invading

becomes greater than optimum temperature for the function of the enzymes, which

causes the enzymes to undergo denaturation. The dispersion forces, dipole-dipole

interactions and hydrogen bonding interactions that are responsible for stabilizing the

secondary, tertiary and quaternary structures of the enzyme (protein) are broken,

which causes it to unravel into a simple polypeptide chain. As a result, the active site

is no longer available to catalyse reactions. The chemical reactions which bacteria

require for growth and replication no longer occur (or cannot occur as quickly as

required), causing bacterial growth to be inhibited and bacterial cell death.

(4 marks) [KA3]


QUESTION 4

Molecules involving the amide functional group are commonly found in a range of everyday

materials and products.

a) N,N-diethyl-m-toluamide is the active ingredient in a popular brand of insect repellent. Its

structure is given below.



N,N-Diethyl-m-toluamide

i) Draw and clearly label the carboxylic acid and amine that are used to produce N,N-

Diethyl-m-toluamide.

(2 marks) [KA2]

b) Kevlar is a strong material that is found in body armour and protective clothing. It is made

up of polymer chains that consist of benzene rings joined by amide links. These polymer

chains are formed from a condensation reaction of benzene-1,4-dicarboxylic acid with 1,4-

diaminobenzene. The structures of these monomers are shown below.

Benzene-1,4-dicarboxylic acid 1,4-diaminobenzene

i) Write the equation for a condensation reaction of benzene-1,4-dicarboxylic acid

with 1,4-diaminobenzene. Circle the amide link in the final product.

(2 marks) [KA2]



ii) Kevlar polymer chains are arranged parallel to each other. Using a diagram to

support your answer, explain the interactions that occur between polymer chains

which contribute to the strength of Kevlar.

The strength of Kevlar comes from the strong hydrogen bonding interactions which

occur between adjacent chains of Kevlar polymer. The hydrogen atoms in the amide

links of the polymer chain form hydrogen bonds with the carbonyl group in the

amide links of the adjacent polymer chain. Since Kevlar is made of repeating

benzene rings, additional strength also comes from the stacking interactions between

the benzene rings in adjacent chains. (4 marks) [KA4]


– END OF TEST –

- Stage 2 Chemistry, Topic 3 -

ESTERS, AMIDES, TRIGLYCERIDES AND PROTEINS

Ester functional group

Name and draw methyl and ethyl esters

Polyesters

Ester Preparation: Condensation Reaction (Carboxylic acid + alcohols)

- Reflux

- Trace of Concentrated sulphuric acid in preparation of esters

Ester hydrolysis – acidic and alkaline conditions

Amide functional group

Draw structural formula of amide

Draw structural formula of polyamide

- Define polyamide

Amide Preparation: condensation reaction (carboxylic acid + amine)

Amide hydrolysis – acidic or alkaline conditions

Define triglyceride

- Fats and oils

- Triesters, three different fatty acid chains and propane backbone

Draw edible oil or fat given the structural formula of carboxylic acid which it is derived

Writing structural formula in condensed form

Triglycerides hydrolysis

- Hydrolysis for energy source

- Lipase

- Identify alcohol and fatty acid products

Saturated triglycerides

Unsaturated triglycerides

Using bromine or iodine to determine saturation

- Iodine and bromine numbers

- Draw structural formula of reaction product

Effect of saturation on melting points of edible oils and fats

Converting liquid triglycerides to triglycerides of higher melting point

- Explain roles of the following in hydrogenation:

1. Pressure

2. Temperature

3. Catalyst

Alkaline hydrolysis of triglycerides

- Carboxylate ions – hydrophobic and hydrophilic regions

- Micelle formation

- Uses of micelles – dissolve and move non-polar substances.

Define protein

General structure of amino acids

- Acidic and basic properties

- Draw product of self-ionisation

Condensation Reaction – formation of polypeptide chains

Peptide bonds

- Draw structural formula of protein chain

Protein structure: Primary, secondary, tertiary and quaternary formations

- Secondary interactions – hydrogen bonding

- α-helix and β-pleated sheet formations

Denaturation of proteins

- Define denaturation

- Explain how proteins are effected by:

1. pH

2. temperature

LAB – PREPARATION OF ESTERS NAME________________

An ester is a chemical compound that is formed when an organic acid reacts with an alcohol. Esters frequently have distinctive odors, and are found in the flavorings of many fruits and plants. The reaction between an organic acid and an alcohol is shown in Figure 1.

R1

C

O

OH

+ O HR2

R1

C

O

O R2

+ O HH

Organic Acid Alcohol Ester Water+ +

Figure 1. The Reaction Between An Organic Acid and Alcohol to Form an Ester and Water In the diagram, R and R' represent organic groups such as hydrocarbons. The -OH group from the acid combines with the -H from the alcohol producing water molecules. The R'-O- group from the alcohol then attaches to the carbon on the acid forming the ester. The reaction is catalyzed by adding some concentrated sulfuric acid, H2SO4. Concentrated sulfuric acid is a strong dehydrating agent, and helps the reaction by removing the water molecules as they are formed. If acetic acid and methanol are reacted, the reaction shown in Figure 2 occurs. The product is called methyl acetate. The systematic name for acetic acid is ethanoic acid, and the product is also known as methyl ethanoate.

CH3

C

O

OH

+ O HCH3 + O HH

Acetic Acid Methanol Methyl Ethanoate

Water+ +

CH3

CH3

C

O

O

Figure 2. The Reaction between Acetic Acid (Ethanoic Acid) and Methanol In this experiment we will prepare small quantities of several esters. The esters will be identified by their distinctive odors. Then we will prepare a larger quantity of the ester ethyl acetate (ethyl ethanoate) and purify it by distillation. Safety Most of the organic acids and alcohols have slightly noxious vapors. Butyric acid and Glacial Acetic Acid should be used in the hood. Sulfuric acid is highly corrosive to clothing and skin. Treat it with great care Glacial Acetic Acid has very irritating fumes. Deal with it in a fume hood only Chemicals Part 1: Various combinations of acids and alcohols will be used which may contain the following: Organic acids: Formic acid (methanoic acid, HCOOH), Acetic acid (ethanoic acid, CH3COOH), Butyric acid (butanoic acid, C3H7COOH), Salicylic acid (C6H4(OH)COOH) , Anthranilic acid (C6H4(NH2)COOH) Organic alcohols: Methyl alcohol (methanol, CH3OH), Ethyl alcohol (ethanol, CH3CH2OH), Butyl alcohol (n-butanol, n-amyl alcohol, C4H9OH), Isopentyl alcohol (isopentanol, isoamyl alcohol, [(CH3)2CHCH2CH2OH], Octyl alcohol (octanol, CH3(CH2)7OH) Sulfuric acid, concentrated (18 M) Baking soda, NaHCO3, to neutralize acid spills


Part 2: Acetic acid, concentrated, 17.4 M (glacial) Ethanol (ethyl alcohol, denatured alcohol) Sulfuric acid, concentrated (18 M) Saturated Sodium carbonate, Na2CO3 Baking soda, NaHCO3, to neutralize acid spills Equipment Part 1: Test tubes, 13- x l00-mm Beaker,400-mL Beaker, 250-mL Hot plate or Bunsen burner, ring and wire gauze Part 2: Erlenmeyer flask, 125-mL Boiling stones Condenser with fittings Distilling flask Thermometer Clamps Beaker, 600-mL for water bath Hot plate, or Bunsen burner, ring and wire gauze Ring Stand Test tube, 18 x 150-mm and cork stopper Separatory Funnel Stoppers 50 mL beaker Procedure Part 1. Microscale preparation of some esters. 1. Prepare a hot water bath. Fill a 400-mL beaker about half full with water. Heat the water to boiling, and then turn off the flame or the hot plate. 2. Prepare the ester. Place 10 drops of one of the organic acids in a dry test tube. If using a solid acid, use a small spatula full, about 0.08 g. Add 10 drops of one of the alcohols. Add 2 drops of concentrated sulfuric acid. Put the test tube into the beaker of hot water and let stand for five minutes. The odor of the ester is more easily detected when the ester is mixed in some water. Never try to directly smell the ester while it is still hot. Put about 100 mL of water in a 250-mL beaker. Pour the contents of the test tube into the beaker and swirl it to mix the contents. Carefully smell the ester after it is mixed with water by waving some of the vapors toward your nose. Can you identify the odor? In your laboratory record, give the name and formula of the acid and alcohol used, give the name and formula of the ester produced, and identify the odor of the ester if you can, or describe its odor. Prepare as many of the esters as your teacher directs. Part 2. Preparation and purification of ethyl acetate (ethyl ethanoate). 1. Preparation of ethyl acetate. In a 125-mL Erlenmeyer flask, place 10 mL ethanol, 12 mL glacial acetic acid, 15 drops of concentrated sulfuric acid (18 M), and a boiling stone. Fill the 600 mL beaker about 2/3 full of water, place it on the heat source, and heat it to boiling. Obtain a condenser, making sure the stopper on it fits your 125 mL flask. Using the ring stand and a clamp, clamp the condenser in a vertical position, with the bottom of the condenser inside the flask just below the stopper. When the condenser is inserted in this manner it acts as a reflux condenser, allowing the vapors of the mixture to condense and return to the reaction vessel. Slowly run cold water through the condenser, in at the bottom and out the top. Gently lower the apparatus so the flask sits in the hot water bath. Once the mixture in the Erlenmeyer flask is gently boiling, allow it to reflux for about 10 minutes. Cool the mixture.


2. Distillation of ethyl acetate. Pour the mixture (including the boiling stone) into a distilling flask and connect the condenser to the side arm of the flask. Insert a thermometer in a stopper in the top of the flask with the thermometer bulb even with the side arm of the condenser. Heat the bottom of the distilling flask in the hot water bath until no more distillate is coming over. Record the temperature at which the distillation begins (the first drop comes out of the condenser) and the temperature at the end of the distillation (dripping stops and the temperature changes again). The boiling point of ethyl acetate is 77oC. Compare this to your distillation temperature. 3. Separation of the ethyl acetate from alcohol. Make sure the 50 mL beaker is clean and dry. Measure the mass of the beaker and set it aside. During the distillation some of the unreacted alcohol will distill along with the ethyl acetate. Ethanol is very soluble in a saturated solution of sodium carbonate, while the ethyl acetate is only slightly soluble. Pour about 10 mL of saturated sodium carbonate solution into a separatory funnel. Add the distillate, stopper and shake for a minute. Turn the separatory funnel upside down and open the stopcock to vent the system. Shake a second time, again inverting the separatory funnel and venting the mixture. Separate the two layers by holding the funnel right side up and opening the stopcock until the first layer comes out. The layer containing the unreacted alcohol/sodium carbonate waste is more dense, so it will be on the bottom of the separatory funnel, and will therefore come out first. Dispose of this layer down the sink. Open the stopcock again, letting the other layer (ethyl acetate) go into the 50 mL beaker, and measure the mass of the ethyl acetate produced. Pour a little of the ethyl acetate into 200 mL of water and cautiously note its odor. Disposal The solutions used to prepare the esters can be safely washed down the sink with a large amount of water according to Flinn Suggested Disposal Method #26b. The ethyl acetate can be saved and used as a solvent, or can be evaporated in the fume hood according to Flinn Suggested Disposal Method #18a. See the appendix. Discussion In your laboratory report include all of your observations, and answer the following questions: 1. Write a complete, balanced reaction for the reaction you did in Parts 1 & 2. Make sure to include the names of each of the substances as well as the Lewis Structure. See the “materials” list on page 1 of this lab for formulas of reactants. 2. The density of ethanol is 0.79 g/mL. The density of acetic acid is 1.05 g/mL. Assuming that each substance was a pure substance, calculate the moles of each reactant used in part 2. Determine the limiting reactant, and calculate the theoretical yield of ethyl acetate. Use the actual yield to determine the percent yield of product. 3. Why was sulfuric acid added to the mixture of acid and alcohol?

Skills and Applications Task: Topic Test · 2018-08-28 · Brianna Lush (a1667331) Chemistry Curriculum and Methodology A Term 1, 2017 STAGE 2 CHEMISTRY Skills and Applications Task:

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