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Евразийский национальный университет им. Л.Н. Гумилёва

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Can a chemical reaction produce electricity?

Date : ...............................................................

Partners : ...............................................................

...............................................................

Grade : ...............................................................

PURPOSE : To establish two half-cells and measure the voltage existing between them.

EQUIPMENT and MATERIALS:

Equipment		Chemicals and Other Materials
• Beaker, 250 mL	(2)	• Zinc electrode	• Potassium nitrate solution, 1 M
• U - tube	(1)	• Copper electrode	• Emery paper
• DC milli voltmetre	(1)	• Zinc sulphate solution, 1M	• Cotton
• Crocodile leads	(2)	• Copper(II) sulphate solution, 1M

PRE-LAB DISCUSSION

In many redox reactions, there is a complete transfer of electrons from the substance (being oxidised) to the substance (being reduced). If the electrons can be made to travel through an external conductor, during this transfer an electric current will be established in the conductor. In electrochemical cells, the two half reactions, oxidation and reduction reactions, are carried out in separate vessels, called

half cells. The two half cells are connected externally by metal wire attached to the two electrodes. In order to have a complete electrical circuit, electrons must be free to flow from one half cell to the other. This is made possible by connecting the solutions in the two half cells with a salt bridge. The complete system is called an electrochemical cell or simply a chemical cell.

PROCEDURE

Set up

—Clean the Cu and Zn electrodes with emery paper to get shinning surface.

Figure

—Fill a 250 mL beaker half full with 1M copper(II) sulphate solution and immerse Cu electrode in the solution.

Experiment – 59 Can a chemical reaction produce electricity?	153

—Fill another 250 mL beaker half full with 1M zinc sulphate solution and immerse Zn electrode into the solution.

—Fill U-tube with 1M potassium nitrate solution and close the openings with cotton lumps.

—Invert the U-tube and place the openings of it in the beakers as shown in the Figure.

—Connect the electrodes, voltmetre and switch with crocodile leads.

Procedure

1.Close the circuit by switching on.

Note: If the needle of voltmetre is deflected in the wrong direction reverse the connections.

2.Read and record the voltage immediately in “Observations and Data Tables”.

3.Wait for 10 minutes and switch off the circuit.

4.Disconnect the electrodes and examine the surface of the electrodes. Note your observations in “Observations and Data Tables”.

OBSERVATIONS AND DATA TABLES

1.Note your observations.

...........................................................................................................................................................................................

2.Record your observations in the table.

Read voltage	Appearance of copper electrode	Appearance of zinc electrode


.........................	..................................................	..................................................

EVALUATIONS AND CONCLUSIONS

1.Indicate the anode and the cathode of the cell.

Anode : ........................................................ Cathode : ........................................................

2. Write the reactions that take place on the surface of the electrodes and overall reaction.

Anode	: ....................................................................................................................................................................
Cathode	: ....................................................................................................................................................................
Overall	: ....................................................................................................................................................................

3.Give a reason for why the process actually takes place and in what direction the electron actually flow.

...........................................................................................................................................................................................

4.Compare the theoretical and the experimental values and explain the difference.

...........................................................................................................................................................................................

5.Explain the role of the salt bridge in the cell.

...........................................................................................................................................................................................

Experiment – 59 Can a chemical reaction produce electricity?

154

Can a metal be coated with another metal by electricity?

Date : ...............................................................

Partners : ...............................................................

...............................................................

Grade : ...............................................................

PURPOSE : To coat iron nail with copper metal by electricity in order to protect from corrosion.

EQUIPMENT and MATERIALS:

Equipment		Chemicals and Other Materials
• Beaker, 250 mL	(1)	• Copper electrode
• Tweezers	(1)	• Iron electrode
• Power supply, (3-12 V)	(1)	• Copper(II) sulphate
• Crocodile leads	(1)	• Sulphuric acid, 3M
• Petri dish	(1)	• Hydrochoric acid, 1M
• Spatula	(1)	• Benzene
		• Distilled water

• Emery paper

• Filter paper

PRE-LAB DISCUSSION

Metals are coated with another metals to secure improved appearance or greater resistance to corrosion. This is called electroplating. According to this method, a metal object which serves as the cathode in a salt solution is covered

with another metal coating in the course of an electrolysis. The advantage of the method is that a permanent coating can be obtained.

PROCEDURE

Set-up	Figure

—Clean the iron and copper electrodes with emery paper until they have continuous shining surface.

—Wet a piece of cotton with benzene, then the electrodes with benzene.

Note: From now on, only touch the electrodes with the tweezers.

—Put the iron electrode in the petri dish and add hydrochloric acid until the electrode is just covered.

—After about one minute, turn the electrode around with the help of tweezers.

Note: Be sure that the surface of the iron electrode is completely treated by hydrochloric acid about one minute.

—Hold the iron electrode with tweezers and put it onto the filter paper and let it to dry .

—Place two spatulas of copper(II) sulphate into the 250 mL beaker. Add 50 mL distilled water and then add 50mL sulphuric acid.

Experiment – 60 Can a metal be coated with another metal by electricity?	155

Caution: Handle the acids with great care. They are corrosive.

—Take the iron electrode with tweezers and rinse it with distilled water.

—Assemble the apparatus as seen in the Figure.

Note: Connect the iron electrode to the negative pole of the power supply.

Procedure

1.Arrange the power supply to the 6 V then switch on it for ten minutes. Record your observations in “Observations and Data Tables”.

2.Switch off the power supply. Disconnect the iron electrode and rinse it with distilled water. Dry it with filter paper.

3.Polish the electrode with emery paper. Record your observations in “Observations and Data Tables”.

OBSERVATIONS AND DATA TABLES

1.Note your observations.

...........................................................................................................................................................................................

EVALUATIONS AND CONCLUSIONS

1.Draw the conclusions from the observations.

...........................................................................................................................................................................................

2.What are the advantages and disadvantages of this process?

...........................................................................................................................................................................................

3.Can this process be used to obtain highly pure metals? Explain.

...........................................................................................................................................................................................

4.List some metals with their coating metal in your daily life.

...........................................................................................................................................................................................

Experiment – 60 Can a metal be coated with another metal by electricity?

156

What is the common element in organic compounds?

Date : ...............................................................

Partners : ...............................................................

...............................................................

Grade : ...............................................................

PURPOSE : To detect the common element, carbon, in several organic compounds.

EQUIPMENT and MATERIALS:

Equipment		• Boss head	(2)	Chemicals and Other Materials
• Test tubes	(4)	• Burner	(1)	• Sugar
• Test tube rack	(1)	• Spatula	(1)	• Wood shavings
• Support base	(2)	• Right-angled glass tube	(1)	• Starch
• Support rod	(2)	• Rubber stopper, with one hole	(1)	• Copper(II) oxide
• Universal clamp	(2)	• Protective glasses	(1)	• Lime-water (Ca(OH)2 solution)

PRE-LAB DISCUSSION

Organic compounds are compounds of carbon that contain either carbon-carbon bonds or carbon-hydrogen bonds or both. Thousands of carbon compounds are found in living organisms or have been produced by chemists, and about five million organic compounds have been characterised.

Organic compounds generally contain carbon, nitrogen and hydrogen in combination with a few other types of atoms, such as oxygen, sulphur, phosphorus and halogens.

PROCEDURE

Set up

Figure

—Place a test tube in the test tube rack and fill one third of it with lime-water.

—Place another three test tubes in the test tube rack and number them from 1 to 3.

—Put a half spatula of copper(II) oxide into each numbered test tube.

—Then put

—A half spatula of sugar in the Test tube 1

—A half spatula of wood shavings in the Test tube 2

—A half spatula of starch in the Test tube 3

—Then put another a half spatula of copper(II) oxide on top of the organic material in the each numbered test tube.

—Insert the short arm of the right-angled glass tube into the hole of the stopper.

Note: Lubricate the glass tube with glycerol before connecting with rubber stopper.

— Wear protective glasses.

Experiment – 61 What is the common elements in organic compounds?	157

Procedure

1.Take the test tube 1 and fit the rubber stopper with right-angled glass into its opening.

2.Clamp the test tube 1 horizontally on the support rod and immerse the long arm of the right-angled tube into the the test tube containing lime-water in it as seen in the Figure.

3.Heat the test tube 1 with a small hot flame for about 3 minutes.

4.Observe the lime-water and observe the cooler part of the test tube-1 for any drops of moisture. Record your

observations in the Table in “Observations and Data Tables”.

Note: Take the long arm of the right-armed tube out of the lime water before extinguishing the burner.

5.Stop heating and repeat the procedure for the other materials in test tube 2 and 3 with fresh lime-water.

Note: Air the room after experiment because unpleasant gases may evolve.

OBSERVATIONS AND DATA TABLES

1.Note your observations in the table.

Organic materials	For drops of moisture	Lime-water


Sugar		...............................................................
	...............................................................

Wood shavings		...............................................................
	...............................................................

Starch		...............................................................
	...............................................................

EVALUATIONS AND CONCLUSIONS

1.What is the role of copper(II) oxide in the experiment? Explain.

...........................................................................................................................................................................................

2.Draw a conclusion that which element is the basic element for all organic materials.

...........................................................................................................................................................................................

3.Which other elements can be found in a organic compounds, mostly? Give examples.

...........................................................................................................................................................................................

4.Write the reaction equation that takes place in the lime-water.

...........................................................................................................................................................................................

Experiment – 61 What is the common elements in organic compounds?

158

How can nitrogen be detected in organic substances?

Date : ...............................................................

Partners : ...............................................................

...............................................................

Grade : ...............................................................

PURPOSE : To examine organic compounds for nitrogen content.

EQUIPMENT and MATERIALS:

Equipment				Chemicals and Other Materials
• Test tubes	(3)	• Boss head	(1)	• Urea
• Dropper	(1)	• Burner	(1)	• Hair
• Test tube rack	(1)	• Spatula	(1)	• Bread, dry
• Support base	(1)	• Protective glasses	(1)	• Sodium hydroxide, 6M
• Support rod	(1)			• Red litmus paper
• Universal clamp	(1)			• Distilled water

PRE-LAB DISCUSSION

Many organic compounds contain (basic) nitrogen. Nitrogen can be detected as ammonia when such substances are decomposed by strong bases. The ammonia can be recog-

nised by its smell and also by the colouration of an indicator such as litmus and the reaction with hydrochoric acid vapour.

PROCEDURE

Set up

Figure-1

—Place three test tubes in the test tube rack and number them from 1 to 3.

—Put a half spatula of urea in Test tube 1

—Put a small tuft of hair in Test tube 2

—Put a few dry bread crumbs in Test tube 3

Note: Substance should be well dried.

— Wear protective glasses.

Procedure

1.Add 5-6 drops of sodium hydroxide solution onto urea in the test tube 1. Then clamp the test tube on the support rod as seen in the Figure-2.

2.Moisten a red litmus paper with distilled water.

3.Heat the test tube 1 in the burner flame and hold the wet litmus paper at the mouth of the test tube as seen in the Figure-2. Record your observations in the Table in “Observations and Data Tables”.

Experiment – 62 How can nitrogen be detected in organic substances?	159

Note: Do not inhale any evolved gas.

Figure-2

4.Proceed the experiment for the hair and dry bread, then record your observations in the Table in “Observations and Data Tables”.

Note: Air the room after experiment because produced gas ammonia has unpleasant smell.

OBSERVATIONS AND DATA TABLES

1.Note your observations when heating the substances.

Urea : ......................................................................................................................................................................

......................................................................................................................................................................

Hair : ......................................................................................................................................................................

......................................................................................................................................................................

Bread : ......................................................................................................................................................................

......................................................................................................................................................................

2.Record the change in the colour of the litmus paper.

Urea	: .................................................................	Hair	: .................................................................
Bread	: .................................................................

EVALUATIONS AND CONCLUSIONS

1.Draw a conclusion from your observations.

...........................................................................................................................................................................................

2.Is nitrogen a basic element of organic compounds?

...........................................................................................................................................................................................

3.List some organic compounds containing nitrogen and their importance for life.

...........................................................................................................................................................................................

Experiment – 62 How can nitrogen be detected in organic substances?

160

How can methane be produced in laboratory?

Date : ...............................................................

Partners : ...............................................................

...............................................................

Grade : ...............................................................

PURPOSE : To prepare methane gas from sodium acetate and to examine its properties.

EQUIPMENT and MATERIALS:

Equipment		• Support base	(2)	• Rubber tubing, 20 cm	(1)
• Erlenmeyer flask, 250 mL	(1)	• Support rod	(2)	• Wire gauze	(1)
• Crystallising dish	(1)	• Universal clamp	(3)	• Tripod	(1)
• Test tube	(2)	• Bosshead	(3)	• Protective glasses	(1)
• Dropper	(1)	• Burner	(1)	Chemicals and Other Materials
• Right-angled glass tube	(1)	• Spatula	(1)	• Sodium acetate
• Delivery tube, with tip	(1)	• Rubber stopper, with one hole	(1)	• Soda lime
• Test tube rack	(1)	• Rubber stopper, without hole	(2)	• Potassium permanganate, dilute

PRE-LAB DISCUSSION

Alkanes contain only single covalent bonds. All of the carbon atoms in an alkane have “sp3” hybridisation and are bonded to four other carbon or hydrogen atoms. The two most important natural sources of alkanes are petroleum and natural gas.

The simplest alkane is methane, (CH4). Methane molecule

has four equivalent carbon-hydrogen bonds arranged as tetrahedral. The carbon atom is joined to each hydrogen atom by a sigma ( ) bond. In methane, the “sp3” hybrid orbitals of carbon atom and “s” orbital of hydrogen atoms overlap to form four (sp3-s) C–H sigma bonds.

PROCEDURE

Set up

—Put an erlenmeyer flask on the wire gauze on the tripod as in the Figure.

—Fill the two third of the crystallising dish with tap water.

—Fill a test tube (or graduated cylinder) with tap water. Close the mouth of the tube with your thumb (or a piece of paper), then sink into the water in the crystallising dish. Open the mouth of the tube. Proceed the same process for another test tube. Clamp them on the support rod as in the Figure.

—Connect the long arm of the right-angled glass tube to the delivery tube with tip by a piece of rubber tubing.

Note: Lubricate glass-rubber connections with glycerol before connection.

—Weigh about 2 g of powdered sodium acetate and 4 g of soda lime. Put them in the erlenmeyer flask and mix well.

Note: If soda lime is not available, weigh 2 g sodium hydroxide and 2 g of dry calcium oxide.

—Assemble the apparatus as in the Figure.

—Wear protective glasses.

Procedure

1.Heat the erlenmeyer flask carefully until a gas evolution is seen. Then manage the flame of the burner as low as possible.

Caution: Do not heat the flask vigorously because the evolved gas is explosive.

2.Allow air to escape from apparatus first about 20 seconds, then slide the tip of the delivery tube under the mouth of the gas collecting test tube.

3.As soon as the gas collecting test tube is full of gas, slide the tip of the delivery tube to the mouth of other inverted tube.

4.Close the test tube containing gas with a rubber stopper and place it in the test tube rack.

Experiment – 63 How can methane be produced in laboratory?	161

5. When the second gas collecting test tube is full	Figure
of gas, close it with rubber stopper and place
of gas, close it with rubber stopper and place
it in the test tube rack.

6.Take the tip of the delivery tube out of the water, then immediately extinguish the flame of the burner.

7.Examine the collected gas and record your observations in “Observations and Data Tables”.

8.Hold the one of the test tubes containing gas then invert it. Remove the stopper and hold the mouth of the test tube at the burner flame. Record your observations in “Observations and Data Tables”.

9.Open the mouth of the second test tube and add 2-3 drops of dilute potassium permanganate solution, then close immediately. Record your observations in “Observations and Data Tables”.

Note: Air the room after experiment.

OBSERVATIONS AND DATA TABLES

1.Note your observations you make while heating the erlenmeyer flask.

...........................................................................................................................................................................................

2.Note your observation when igniting the collected gas.

...........................................................................................................................................................................................

3.Note your observation about the colour of potassium permanganate solution after addition.

...........................................................................................................................................................................................

EVALUATIONS AND CONCLUSIONS

1.Write the equation of the reaction in the production of methane.

...........................................................................................................................................................................................

2.List the observed properties of methane in the experiment.

...........................................................................................................................................................................................

3.What are the common properties of methane and the other alkanes?

...........................................................................................................................................................................................

4.Give some usages of methane in your daily life and in industry with an example.

...........................................................................................................................................................................................

Experiment – 63 How can methane be produced in laboratory?

162

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