Laboratory Manual Introductory Experiments and Procedures



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Part A Titration of HCl -
Solution Trail 1 Trial 2 Trial 3
HCl Final buret reading (mL) ______ ______ ______

Initial buret reading (mL) ______ ______ ______

Volume of HCl added (mL) ______ ______ ______
NaOH

Final buret reading (mL) ______ ______ ______

Initial buret reading (mL) ______ ______ ______

Volume of NaOH added (mL) ______ ______ ______


Part B Titration of H2SO4
Solution Trail 1 Trial 2 Trial 3
H2SO4 Final buret reading (mL) ______ ______ ______

Initial buret reading (mL) ______ ______ ______

Volume of H2SO4 added (mL) ______ ______ ______
NaOH

Final buret reading (mL) ______ ______ ______

Initial buret reading (mL) ______ ______ ______

Volume of NaOH added (mL) ______ ______ ______


Analysis:

1. Calculate the average molarity of the HCl solution. Show all of you work, including units. Your grade will be determined on how close you are to the actual concentration of the HCl. Report your answer to the correct number of significant digits.


2. Calculate the average molarity of the H2SO4 solution. Show all of you work, including units. Your grade will be determined on how close you are to the actual concentration of the H2SO4. Report your answer to the correct number of significant digits.

3. If while performing the titration there was an unseen air bubble in the tip of the buret, describe how your calculated molarity of the acid would differ from the actual molarity. Explain.

Lab # 22 Heat of Combustion Lab


Objective: You will investigate the relationship between the thermal energy released when a fuel burns and its molecular structure.

Hypothesis:

Prior to beginning the experiment, predict which of the fuels that you think will produce the highest heat of combustion and which will produce the lowest heat of combustion,



Procedure:

Follow the same procedure for the following fuels:



Methanol, Ethanol, Kerosene, Biodiesel, and Paraffin Wax
1. Determine the mass of the fuel before burning. (For the candle, mass the candle and the glass plate together.)

2. Hang a clean soda can on the iron ring attached to the ring stand as shown by your instructor.

3. Adjust the height of the soda can so that the can is about 1 inch above the wick of the fuel source.

4. Place 100.0 mL of cold tap water into the soda can.

5. Record the temperature of the water in the can to the nearest 0.2oC.

6. Light the fuel source and heat the water for 2 minutes. Gently stir the water as it heats up and monitor the temperature. Do not allow the water to boil.

7. Extinguish the flame and record the highest temperature the water attains.

8. Re-mass the fuel and determine the mass of fuel that was burned.

9. Pour the water out of the can and clean off any soot from the bottom of the can.

Data:

Fuel

Final H2O Temp (oC)

Initial H2O Temp (oC)

Temp Change

(oC)



Final mass of fuel (g)

Initial mass of fuel (g)

Mass of fuel burned (g)

Biodiesel





















Ethanol




















Kerosene




















Methanol




















Paraffin





















Calculations:
Calorimetry a method in which you calculate the thermal energy released from a combustion reaction by measuring the amount of heat absorbed by a given mass of water. Water was used to capture the heat form the burning fuel because water has such a high specific heat. The specific heat of the substance is defined as the amount of energy required to raise one gram of that substance one degree Celsius. The specific heat of water is 1.00 calorie/g . oC or 4.184 J/g . oC.
To calculate the amount of heat that the water absorbed you need to know three values:
1. The mass of the water that was heated. (Remember that the density of water is

1.00 g/mL, so 100.0 mL of water is the same as 100.0 g of water.)

2. The specific heat of water; you will be using the 4.184 j/g.oC value.

3. The change in the temperature of the water as it was heated.


The formula for calculating the amount of heat absorbed by the water is:
H = mw x Cp x DT
Where, mw = mass of water, Cp = specific heat of water, DT = change in temp of water

The units cancel to give the heat absorbed in units of Joules. It is typical to divide the heat by 1000 to give your answer in kilojoules (kJ)


At this point you have simply calculated the amount of heat absorbed by the water. In order to properly compare the different fuels that you tested, you need to calculate the heat of combustion of each fuel in units of kilojoules per gram (kJ/g). To do this, simply divide the heat absorbed by the water in each trial by the mass of the fuel burned. This will allow you to determine which fuels released the most heat for every gram of fuel that was burned.
Calculate the heat of combustion in kJ/g for each of the fuels that you tested. Be sure to show all of your work, including the units and report your answers to the proper number of significant digits.
Results for Heat of Combustion Calculations (kJ/g)


Biodeisel

Ethanol

Kerosene

Methanol

Paraffin














Show work here:



Questions:
1. Why was water used in this lab?

2. Why is it important that you do not allow the water to boil during this lab?

3. Rank the fuels from the lowest heat of combustion to the highest.

4. What other factors besides heat of combustion would you consider when choosing the best overall fuel? (List at least 3 additional factors and explain your reasons.)

5. Discuss the assumptions that you made in calculating the heats of combustion and explain how these assumptions may have affected your final results. Be specific!

Grading Rubric:
Lab Technique and Clean-up _____ (10)

Data _____ (10)

Calculations _____ (7)

Results _____ (2)

Questions _____ (8)
Total _____ (37)
Lab # 23 Radioactive Decay and Half-Lives Lab

Procedure
1. Spread out a few paper towels on your table and count the total number of M&M’s provided. (This represents the original number of radioactive atoms.)

2. Place the M&M’s in the cup and then dump them onto the paper towels on the table.

3. Separate the candies with the M&M side up from the ones that are face down. Record the number that are face up (decayed) and face down (undecayed). Place the face down candies back into the cup.

4. Continue dumping the M&M’s and removing the “decayed atoms” until they are all decayed. Each toss represents one half-life.

5. Convert the numbers of undecayed atoms to percentages in your data table.

6. Collect class data for the percentages of undecayed atoms vs. half-lives.

7. Create a graph of % undecayed atoms vs. half-lives. Use different colors to draw two lines; one for your data and one for the class data.
Data:


Half-Lives (tosses)

Number decayed


Number undecayed


Percent undecayed



Average Percent undecayed

class data

0













1













2













3













4













5













6













7













8













9













10













11













12














Percent Undecayed Atoms vs. Number of Half-Lives


































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































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