What is the shape of water? What is autoionization, and how is it important for water? Name the three non-covalent forces discussed in this module. What type of non-covalent interaction is known as the strongest dipole-dipole force? 5.Would the following be a hydrogen donor or acceptor? Or both? How does the strength of London forces change with increasing molecular weight? Explain briefly.

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1.What is the shape of water?

2.What is autoionization, and how is it important for water?

3.Name the three non-covalent forces discussed in this module.

4.What type of non-covalent interaction is known as the strongest dipole-dipole force?

5.Would the following be a hydrogen donor or acceptor? Or both?

6.How does the strength of London forces change with increasing molecular weight? Explain briefly.

7.Calculate the pH of a solution containing 0.12 M of OH– .

8.If a solution contains 0.00023M of H+, then what is the OH – concentration?

9.If a solution contains 1.67 x 10-8 M OH – , then what is H + concentration?

10.A solution contains H+ at a concentration of 1.67 x 10-6 M. Is the solution acidic, basic, or neutral? Explain briefly.

11.What is the concentration, in M, of water as a pure liquid?

12.Define Keq and K w .

13.Identify the acid, conjugate base, and proton in the following reaction.

14.A buffer system has a pKa of 8.5. What is its effective buffering range?

15.A buffer system has [H +] = 1.2 x 10 -6 , [A – ] = 1.2 x 10 -6 , and [HA] = 3.2 x10 -5 . What is its corresponding Ka value?

16.A buffer system has [H +] = 1.2 x 10 -6 , [A – ] = 1.2 x 10 -6 , and [HA] = 3.2 x 10 -5 . What is its corresponding Ka value?

17.Ice melts at room temperature. What is the sign for Δ G in this reaction?

18.Butane combusts in the air by the following reaction: C 4 H 10 (l) + 6.5 O2 (g)⟶ 4 CO 2 (g) + 5 H 2 O (g)  What is the sign (+ or -) ofΔG,ΔH, and ΔS in this reaction?

19.What is the role of ATP in helping a non-spontaneous reaction occur?

Explain in your own words exactly how CRISPR works. Do you agree or disagree that the controversy around CRISPR is similar to the controversy around cloning decades ago? What is the Cas9 RNA base sequence that would attach the CRISPR complex to the following segment of DNA?

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Discussion 4

Overview

CRISPR, Clustered Regularly Interspaced Short Palindromic Repeats, is the transformative gene editing tool that has made significant progress in the last several years. There is much hope and hype around this new technology that may one day eradicate diseases such as Alzheimer’s, cancer, Malaria, and many others. At the same time, controversy shrouds any new progress in the field with many wondering about the bioethical implications of new use of the technology.

Instructions

Watch  the Ted Talk – “How CRISPR lets us edit our DNA” and “What is CRISPR?” with background information on CRISPR and information about the latest developments. As you are watching, think about how you will answer the following questions:

  1. Explain in your own words exactly how CRISPR works.
  2. Do you agree or disagree that the controversy around CRISPR is similar to the controversy around cloning decades ago?
  3. What is the Cas9 RNA base sequence that would attach the CRISPR complex to the following segment of DNA?

 

(Hint: See Section 21.5 of eText)

Perform a separation of plant pigments using thin-layer chromatography. Determine the relative polarity of plant pigments based on the Rf value of the TLC plate. Calculate Rf values of plant pigments. Explain how thin-layer chromatography works.

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Thin Layer Chromatology Lab 6

Overview
In this investigation, students will extract pigments from spinach, then perform thin-layer chromatography to identify the pigments using two solvent solutions and the Rf value of the pigment.

Outcomes
• Perform a separation of plant pigments using thin-layer chromatography.
• Determine the relative polarity of plant pigments based on the Rf value of the TLC plate.
• Calculate Rf values of plant pigments.
• Explain how thin-layer chromatography works.

Identify the atom and its components. Differentiate between elements and compounds formed by ionic or covalent bonds. Differentiate the types of chemical reactions and associated terminology. Describe the structure and function of water and its role in living systems. Differentiate the functional roles of acids, bases, and buffers. Differentiate the structures and functions of major organic molecules.

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Unit student learning outcome

Select two of the unit student learning outcome (USLO) prompts below to respond to in this week’s discussion.
1. Identify the atom and its components.

2. Differentiate between elements and compounds formed by ionic or covalent bonds.

3. Differentiate the types of chemical reactions and associated terminology.

4. Describe the structure and function of water and its role in living systems.

5. Differentiate the functional roles of acids, bases, and buffers.

6. Differentiate the structures and functions of major organic molecules.

Perform a separation of plant pigments using thin-layer chromatography. Determine the relative polarity of plant pigments based on the Rf value of the TLC plate. Calculate Rf values of plant pigments. Explain how thin-layer chromatography works.

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Thin Layer Chromatology Lab 6

Overview
In this investigation, students will extract pigments from spinach, then perform thin-layer chromatography to identify the pigments using two solvent solutions and the Rf value of the pigment.

Outcomes
• Perform a separation of plant pigments using thin-layer chromatography.
• Determine the relative polarity of plant pigments based on the Rf value of the TLC plate.
• Calculate Rf values of plant pigments.
• Explain how thin-layer chromatography works.

0.641 g of a semi-synthetic alkaloid was dissolved in 25 ml of 1% w/v acetic acid and was analysed directly by HPLC. The solution was found to contain 1.42 mg/100 ml of an impurity. What is the level of impurity in % w/w and ppm? Calculate the pH of a buffer system made by dissolving 1.2 g of acetic acid and 0.82 g of sodium acetate in 500 ml of distilled water (pKa of acetic acid = 4.7). Explain how to prepare standard solutions (5 ml each) of NaCl with the following concentrations: 10, 20, 30, 50, 70 ppm. The stock solution has a concentration of 0.05% w/v.

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Assay of paracetamol

Scientific Communication and Professional Skills

Assessed lab report

You are required to write a lab report based on results obtained from this experiment. The lab report will describe and discuss the spectrophotometric assay of paracetamol. The collected data must be presented, analysed, and interpreted. The lab report is followed by a few calculation questions which you need to answer and provide an explanation for your solution. .

Practical details:
The maximum absorbance wavelength (λmax) of paracetamol is 243 nm. In order to assess the content of paracetamol in an unknown sample, we need first to prepare a calibration curve which displays the relationship between absorbance and concentration
You will have the following:

  • Paracetamol stock solution (10 mg/litre) in 5% ethanol/water.
  • Dilution solution 5% ethanol/water
  • Samples containing paracetamol
  • Glassware, volumetric flasks, tubes to prepare your solutions, micropipettes, and UV cuvettes.
  • Preparation of standard solutions

Prepare standard solutions of paracetamol starting from the stock solutions with the following concentrations. The final volume of each solution should be 5 ml.
Calculate the needed volumes of both the stock solution and the dilution solution to prepare your standards 1–5.

Measuring absorbance of standard solutions
Use UV cuvettes for this experiment.
Prepare the spectrophotometer by using the blank solution to give zero absorbance at 243 nm.
You can use the same cuvette to measure the absorbance of standard solutions, starting from the lowest to the highest concentration. Return the solution to its tube after each measurement and tap the cuvette on a clean tissue paper to remove the remaining droplets. Record the absorption values in the following table:

Use the absorbance readings to draw the calibration curve of absorbance vs concentration and find out the regression equation using Excel. Preparation of sample solution
You will be provided with a sample containing unknown amount of paracetamol. Make note of your sample code.
– Preparation of solution A: Weigh out 125 mg of your unknown sample and transfer it carefully into 100ml volumetric flask. Add around 50 ml of the dilution solution (5% ethanol in water) and swirl gently until the powder is completely dissolved. Make the volume up to 100 ml and mix well.
– Preparation of solution B: take 5 ml of solution A using a micropipette and transfer it into a 50 ml volumetric flask. Make the volume up to 50 ml using the dilution solution.
– Preparation of reading solutions C: using the micropipette, measure 500 μl of solution B and make it up to 10 ml with dilution solution. Prepare 3 repeats.
– Use a clean cuvette to measure the absorbance of solution C at 243 nm.
– Record the absorbance values in the following table:

– Use the calibration curve and the regression equation to calculate the percentage of paracetamol in your sample.
– Discuss the reliability and precision of your measurements. Comment on the r– squared value of your calibration curve.
– Discuss the sources of errors in the experiment.

Additional calculation questions:
1– A sample of an infusion was diluted 10 ml to 250 ml and then 10 ml to 200 ml. It was then analysed and was found to contain sodium at 0.789 mg/100 ml. Calculate the concentration of sodium in the original sample in %w/v. The sample was composed of a mixture of sodium lactate and sodium carbonate in equimolar amounts. Calculate the amount of sodium lactate and sodium carbonate in mg/10 ml of the sample (Na = 23, lactate = 89, carbonate = 60) (10 marks)

2– Convert the following concentrations into the required expression (5 marks)

Concentration given Expression required

  • 0.5% NaCl molarity
  • 1 mM of KBr mg/ml
  • 5 mg/100 ml paracetamol molarity
  • 0.15 N H2SO4 g/litre
  • 0.5% ethanol/water (w/v) ppm

3– 0.641 g of a semi–synthetic alkaloid was dissolved in 25 ml of 1% w/v acetic acid and was analysed directly by HPLC. The solution was found to contain 1.42 mg/100 ml of an impurity. What is the level of impurity in % w/w and ppm? (5 marks)

4– Calculate the pH of a buffer system made by dissolving 1.2 g of acetic acid and 0.82 g of sodium acetate in 500 ml of distilled water (pKa of acetic acid = 4.7) (5 marks)

5– Explain how to prepare standard solutions (5 ml each) of NaCl with the following concentrations: 10, 20, 30, 50, 70 ppm. The stock solution has a concentration of 0.05% w/v. (5 marks)

6– The following tables shows the results of an IQ test for two groups of students
Group A 1 2 3 4 5 6 7 8 9 10 11 12 13
IQ 105 108 103 106 106 114 107 104 114 110 111 112 112
Group B 1 2 3 4 5 6 7 8 9 10 11 12 13
IQ 118 118 109 120 109 112 127 106 110 116 115 106 116

Use T–test to examine if there is a significant difference between the average IQs of the two groups at a:
a– 0.05 level of significance
b– 0.001 level of significance
Show your calculations and explain the meaning of results (10 marks)

Draw a diagram depicting what happens to the atoms of elements or molecules of compounds when a chemical change occurs and when a physical change occurs. Explain how the changes differ. Whereas there are some outward signs of a chemical change, many of these can be mimicked by physical changes. What are some more reliable ways by which a chemical change can be distinguished from a physical change?

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Exploring physical and chemical changes

Pre-Laboratory Questions

  1. Explain the difference between a chemical change and a physical change.
  1. List three examples of physical changes and three examples of chemical changes. Explain why these are chemical or physical changes.

 Laboratory Questions

In the following scenarios, tell whether the change being described is a physical or a chemical change, and explain the reasoning behind your answer.

  1. A carbonated beverage container is opened, producing a fizzing sound and carbon dioxide (CO2) bubbles.
  2. Dry ice (solid CO2) is taken from a freezer and placed in an ice bucket at room temperature. With time, the block decreases in size and is surrounded by a visible cloud.
  3. A pastry chef adds a mixture of white vinegar (~5% acetic acid in water) and baking soda (sodium bicarbonate, NaHCO3) to the batter for a red velvet cake to create bubbles that make the cake rise.
  4. A shiny, silvery iron nail turns reddish-brown when left exposed to the weather.
  5. A chemical heat pack is manufactured by sealing water (H2O) and calcium chloride (CaCl2) in separate compartments of a container. When the two components are mixed, the CaCl2 dissolves in the water, producing a large amount of heat.

 General Lab Questions

  1. Draw a diagram depicting what happens to the atoms of elements or molecules of compounds when a chemical change occurs and when a physical change occurs. Explain how the changes differ.

 

  1. Whereas there are some outward signs of a chemical change, many of these can be mimicked by physical changes (e.g., a change in color). What are some more reliable ways by which a chemical change can be distinguished from a physical change?

Demonstrate an understanding of safe working practice through experimental work, including the selection of appropriate methods. Record, interpret and analyse experimental investigations in relation to an original hypothesis and make suitable recommendations for enhancing future work

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Calculating the concentration of an acid

Module learning outcomes
On successful completion of this assessment, you will have met the following module learning outcomes:

 

Knowledge Based Outcomes

 

LO3.  Demonstrate an understanding of safe working practice through experimental work, including the selection of appropriate methods

LO4.     Record, interpret and analyse experimental investigations in relation to an original hypothesis and make suitable recommendations for enhancing future work

 

Skilled Based Outcomes

●       Analytical and problem solving

●       Carrying out experimental work in a safe, reliable and efficient manner

●       Expanding the range of scientific skills and techniques, both quantitative and qualitative

●       Time management, planning and organisational skills

●       Ability to work competently and independently

●       Being aware of own strengths and weaknesses and to recognise when support is needed

 

Assessment criteria:
In order to successfully complete this assessment and meet the above learning outcomes, you must satisfy the following criteria:

 

 

AC3.1       Outline the procedure of an experiment, including an accurate method and list of materials

AC3.2       Identify and explain the independent, dependent and controlled variables in relation to a given experiment

 

AC4.1       Present data clearly and accurately with the use of appropriate tables and graphs

AC4.2       Interpret scientific results and identify potential sources of error, uncertainties, and anomalies

AC4.3       Critique experimental design and processes within a given experiment

AC4.4       Offer suitable recommendations and improvements that can be implemented in future experimental work

 

Describe the role of intermolecular forces in electronic and molecular shapes. How does the presence of lone (unshared) electrons change the electronic shape in the formation of the molecular shape?

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Role of intermolecular forces in electronic and molecular shapes

In Discussion 3, describe the role of intermolecular forces in electronic and molecular shapes. How does the presence of lone (unshared) electrons change the electronic shape in the formation of the molecular shape? Be sure to cite specific examples of this phenomenon on molecules from the VSEPR section of the text, Bb Lab and/or Worksheet. (Insert diagrams or images)

You may comment on one or more of these questions and personal experiences are also welcome. Just start posting and we will see where the conversation takes us! You do not use citations in the body of your posts. These must be in your own words. DO NOT CUT AND PASTE! Keep in mind that your discussion should show me how knowledgeable you are on this topic. Responses should show thought and interest in the post you are responding to. Make sure you engage the original author so they will want to respond. “Great post” or ” agree” are not complete responses.
This is a 20 point assignment. This is an opportunity to earn points by looking at a specific topic and use data to support your opinion. Fair warning: If you give me a half-hearted response, I will give you a half-hearted grade!

Describe the role of intermolecular forces in electronic and molecular shapes. How does the presence of lone (unshared) electrons change the electronic shape in the formation of the molecular shape?

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Role of intermolecular forces in electronic and molecular shapes

In Discussion 3, describe the role of intermolecular forces in electronic and molecular shapes. How does the presence of lone (unshared) electrons change the electronic shape in the formation of the molecular shape? Be sure to cite specific examples of this phenomenon on molecules from the VSEPR section of the text, Bb Lab and/or Worksheet. (Insert diagrams or images)

You may comment on one or more of these questions and personal experiences are also welcome. Just start posting and we will see where the conversation takes us! You do not use citations in the body of your posts. These must be in your own words. DO NOT CUT AND PASTE! Keep in mind that your discussion should show me how knowledgeable you are on this topic. Responses should show thought and interest in the post you are responding to. Make sure you engage the original author so they will want to respond. “Great post” or ” agree” are not complete responses.
This is a 20 point assignment. This is an opportunity to earn points by looking at a specific topic and use data to support your opinion. Fair warning: If you give me a half-hearted response, I will give you a half-hearted grade!
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