Use the value of enthalpy you determined for CaCl2 to calculate what quantity of salt will be needed to make a chemical hot pack. Assume using 100 g (100 mL) of water and changing the temperature from 25 °C to 60 °C. Show all calculations.

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The Fundamentals of Calorimetry

Student Name

  • Date
  • Purpose
  • Procedure
  • Experimental Data

Table 1

Time

(min)

 Trial 1

Temp. °C

 Trial 2

Temp. °C
1    
2    
3    
4    
5    
6    
7    
8    
9    
10    

Insert graph of the data from Data Table 1, plotting temperature vs. time, and use the Y intercept to find the temperature at time 0 when the two volumes of water are mixed.

 

Table 2

  Trial 1 (include units) Trial 2 (include units) Calculations (for Trial 1)
Initial temperature of cold water      
Initial temperature of warm water      
Temperature at time 0 from graph, T0      
Heat lost by hot water      
Heat gained by cold water      
Heat gained by calorimeter      
Temperature change of calorimeter      
Heat capacity of calorimeter      
Average Heat capacity of calorimeter    

 

Table  3

Report data with correct units.  Show calculations below the table

  5g CaCl2 10g

CaCl2

 15g

CaCl2

 5g

NH4Cl

 10g

NH4Cl

 15g

NH4Cl
Mass of water

 

            
Mass of salt

 

            
Moles of salt

 

            
Initial Temperature

 

            
Final Temperature

 

            
Change in Temperature            
Heat released/absorbed by water            
Heat released/absorbed by the calorimeter            
Enthalpy of solution

 

            
Molar Enthalpy of solution            
Average molar enthalpy of solution    

Show calculations for first column:

  • Moles of salt
  • Heat released/absorbed by the solution
  • Heat released/absorbed by the calorimeter
  • Enthalpy of solution (J)
  • Enthalpy of solution (kJ)
  • Molar Enthalpy of solution
  • Average molar enthalpy of solution

Insert graphs of ΔT vs. grams of salt for NH4Cl

 

Lab Questions

  1. What sort of relationship exists between the temperature change and the mass of the salt dissolved? Explain your answer.
  2. The actual molar enthalpy of solution for calcium chloride is -81.3 kJ/mol, whereas the molar enthalpy of solution of ammonium chloride is 14.8 kJ/mol. Calculate the percent error of your results. Show the calculations.
  3. Use the value of enthalpy you determined for CaCl2 to calculate what quantity of salt will be needed to make a chemical hot pack. Assume using 100 g (100 mL) of water and changing the temperature from 25 °C to 60 °C. Show all calculations.
  4. Use the graph you drew for NH4Cl to determine the amount of salt needed to make a chemical cold pack. Assume using 100 g (100 mL) of water. The temperature should go down to 3.0 °C from a room temperature of 25 °C. Show all calculations.
  5. Suggest practical ways in which the calorimeter or lab protocol could be improved to decrease percent errors.

Write a report on titrimatic analysis.

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Titrimatic analysis

Write a report on titrimatic analysis.

List everything needed to complete your experiment. Describe the steps you completed during your investigation.

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Format for Laboratory Report

Title Page

  • The title of the experiment
  • Your name
  • Your instructor’s name
  • The date the lab was performed or the date the report was submitted

Title

The title says what you did. It should be brief (aim for ten words or less) and describe the main point of the experiment or investigation. An example of a title would be: “Effects of Ultraviolet Light on Borax Crystal Growth Rate”. If you can, begin your title using a keyword rather than an article like ‘The’ or ‘A’.

Introduction / Purpose

Usually, the Introduction is one paragraph that explains the objectives or purpose of the lab. In one sentence, state the hypothesis. Sometimes an introduction may contain background information, briefly summarize how the experiment was performed, state the findings of the experiment, and list the conclusions of the investigation. Even if you don’t write a whole introduction, you need to state the purpose of the experiment, or why you did it. This would be where you state your hypothesis.

 

Materials

List everything needed to complete your experiment.

 

Methods

Describe the steps you completed during your investigation. This is your procedure. Be sufficiently detailed that anyone could read this section and duplicate your experiment. Write it as if you were giving direction for someone else to do the lab. It may be helpful to provide a Figure to diagram your experimental setup. DO NOT USE “I”, “YOU”, “WE”, “US” OR “THEY.”

 

Data

Numerical data obtained from your procedure usually is presented as a table. Data encompasses what you recorded when you conducted the experiment. It’s just the facts, not any interpretation of what they mean.

 

Results

Describe in words what the data means. Sometimes the Results section is combined with the Discussion (Results & Discussion).

 

  1. Discussion or Analysis

Discuss the experiment and the results obtained. This does not mean you simply report the results again, but rather interpret and discuss their significance. Results should also be compared with those in the literature, if possible. (Be sure to give proper citations). If problems were encountered during the course of the experiment, how might they be rectified in the future? Are there any other things we could do to make this a better experiment or to more specifically address the initial question posed? Are there any better techniques available that would allow one to more accurately generate data? Is there more than one way to explain the results? Your results may support your initial hypothesis, but there may be more than one conclusion that could be drawn from your results. Lastly, do not spend enormous amounts of time explaining data that cannot be explained!

Conclusions

Most of the time the conclusion is a single paragraph that sums up what happened in the experiment, whether your hypothesis was accepted or rejected, and what this means.

 

Figures & Graphs

Graphs and figures must both be labeled with a descriptive title. Label the axes on a graph, being sure to include units of measurement. The independent variable is on the X-axis. The dependent variable (the one you are measuring) is on the Y-axis. Be sure to refer to figures and graphs in the text of your report. The first figure is Figure 1, the second figure is Figure 2, etc.

References

If your research was based on someone else’s work or if you cited facts that require documentation, then you should list these references.

Indicate which electrode will be the anode (electrodes are labeled as 1 and 2). Explain why.

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CHEM 100 Spring 2023 Exam 2 Free Response Section (30 points)

  1. Consider the following galvanic cell. Based on the electron flow,
    1. Indicate which electrode will be the anode (electrodes are labeled as 1 and 2) (0.5 points). Explain why.
    2. Indicate which electrode will be the cathode (electrodes are labeled as 1 and 2) (0.5 points). Explain why.
    3. If Pt and Au were the electrodes, which would be the anode? Which would be the cathode? Why? Please refer to the electronegativity chart on page 1 (2 points).
    4. Which is the correct half reaction for Pt (0.5 points)?

Pt2+ + 2e– → Pto

Pto – → Pt2+ + 2e–

    1. Which is the correct half reaction for Au (0.5 points)?

Au3+ + 3e– → Auo

Auo – → Au3+ + 3e–

    1. Write the balanced overall redox reaction for the Pt and Au Galvanic Cell. Please show your work. How many electrons are transferred (3 points)?

Base on your decision about which source to choose based on whatever criteria you wish – is it a company based in the US (meaning it’s probably easier to get it shipped)? Is it the least expensive? Do they have it in stock, or will it be synthesized on demand?

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Use of the Chemical Literature

Assignment

Part 1
Search for the first 10 compounds from Assignment 10 using SciFinder. Like last week, you can use whatever method you wish. Ideally find the source YOU would choose to purchase each compound from and take a screen grab of the Commercial Source Information for each. You can base your decision about which source to choose based on whatever criteria you wish – is it a company based in the US (meaning it’s probably easier to get it shipped)? Is it the least expensive? Do they have it in stock, or will it be synthesized on demand? Your choice.

As an important note, if the compound you’re searching for does not have any commercial sources, just take a screen grab that shows that there aren’t any commercial sources available (for example, there is no “Suppliers” link).

Part 2
Search for the same 10 compounds (from Part 1 of this assignment) using Google Shopping, It’s worth noting that, just like everything associated with Google, ads will try to guide you to
certain vendors, so don’t be afraid to scroll a bit! Compile all of your screen grabs in order and separated by labeled parts onto a single document.

In your own words, explain how scientists measure the atomic radius? What are the factors that affect the atomic radius?

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Rayon Atom MB

Answer the following questions in 1.5 pages:

Task on the atomic radius

  1. In your own words, explain how scientists measure the atomic radius?
  2. What are the factors that affect the atomic radius? Name and define each of these factors…
  3. How do the trends in atomic radius show up in the TP (increases or decreases from top to bottom and from right to left); make a sketch of the TP and use arrows to show the increase in AR.
  4. Arrange the following elements in order of increasing atomic radius and explain your choice. Carbon, aluminum, oxygen, potassium.
  5. In your own words, explain the following terms: a)Screen effect: b)The effective nuclear charge

How many elements are in periodic table?

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Periodic Table

How many elements are in periodic table?

Can this be balanced algebraically? If so, can you show the steps? NO2 + H20 –> HNO3 + NO

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Balancing an Equation Algebraically

Can this be balanced algebraically? If so, can you show the steps? NO2 + H20 –> HNO3 + NO

Discuss melting point measurements. What steps did you take to minimize potential sources of error in these measurements? Describe how you determined the mechanism of this reaction. How did you rule out the alternative pathways?

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Bromination of trans–Cinnamic Acid (10 pts)

Compose the notebook page using the following notebook modules: Objectives, Safety Data,
Compound Structures, Results, and Discussion and Conclusion

Objectives (1 pt) should identify the overall goal of the lab and briefly explain what methods are used and why they are used, in this experiment.

In Safety (1 pt), include hazards information for all compounds listed on Canvas in Safety Data Sheets section for this lab:
– Bromine
– DCM
– Cinnamic Acid
– 1–Hexene

In Compound Structures (2 pts), draw the reaction equation for bromination of trans–cinnamic acid with Br2. Include the reaction intermediate or transition state that leads to the product obtained in your experiment. Refer to lecture slides describing three alternative mechanistic pathways and pick the one that you think operates in your reaction.

In Results part (1 pt), include all information you recorded in Data Sheet you received in the lab.

In Discussion (4 pts):
– Show and explain percent yield calculations.
– Discuss melting point measurements. What steps did you take to minimize potential sources of error in these measurements?
– Describe how you determined the mechanism of this reaction. How did you rule out the alternative pathways?

In Conclusion (1 pt), summarize key points, methods, and include main data.

Which of these two acomplished men has a more impactful social effect and why? Is your impression of these two based on inherent advantages one had over the other based on their pedagry or lineage? Did one perform as expected and is another extrodinary? Is it fair to expect more of those who have advantages?

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Discussion Board

“To whom much is given, much is required” is a bible quote (Luke 12:48 ) which is often used to explain why we expect more from those who are born to some advantage.

Compare the backgrounds of McBay, Henry C. Encyclopedia.com , Henry C. McBay Award (nobcche.org) and Dr. St. Elmo W. Crawford Jr.

Which of these two acomplished men has a more impactful social effect and why? Is your impression of these two based on inherent advantages one had over the other based on their pedagry or lineage? Did one perform as expected and is another extraordinary? Is it fair to expect more of those who have advantages?