Introduction to Chemistry Laboratory_2023

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University of British Columbia *

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154

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Chemistry

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Dec 6, 2023

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1 Topics Discussed: 1. Introduction 2. Chem 154 Lab Website 3. Chem 154 at a Glance 4. Lab Schedules 5. Structure of an Experiment: Pre- & In- Labs 6. Experimental Design Form 7. Assignments and On-Line Introductory Material 8. Concept Mapping 9. Writing a Lab Report 10. Lab Instruction 11. Other Information for Chem 154 Labs 12. Procedure for Making Up a Missed Lab 13. Safety in the Lab 14. Significant Figures 15. Precision and Accuracy 16. Errors 17. The International System of Units There are over 800 students in CHEM 154. This vast student body possesses a very diverse range of chemical knowledge and experience. The lab program has been designed with the “average” student in mind. While certain components of the On-line Introductory material and some of the discussions in this lab manual have been designed primarily for students with little experience in chemistry, it is recommended that all students review this information. Introduction to the CHEM 154 Laboratory 1. Introduction 2. Chem 154 Lab Course Website Check the Chemistry 154 Laboratory Canvas for important announcements. Go to your “Course List” in Canvas and choose Chemistry 154 Online Labs.

2 3. Chemistry 154 at a Glance All Chem 154 students will follow the same schedule for attempting the experiments. Lab program consists of 5 in-lab sessions (3 hours each) alternating with 5 pre-lab weeks . Your designated lab schedule will tell you which experiments to do each week. Laboratory Reports or Post lab assessment (PLAs) will be done in two parts 1. Online Canvas quiz about the experiment. 2. Online submission with answers to be written or typed out and uploaded on Canvas. These are due two days after you complete your in-lab session. For example, if you complete an in-lab session on Monday from 2-5pm, your PLAs (both parts) will be due by 6pm on Wednesday that week. Within the PLAs, you may be assigned to groups for varying your assessment questions/ data. 4. Lab Schedules Each student will be given a lab schedule to follow. Please make sure you check your schedule carefully as each schedule follows a different combination of experiments on different dates. ***There is a mark penalty for preparing for the wrong lab and a make-up lab is not guaranteed*** 5. Structure of an Experiment The laboratory experiments that you will be performing in the course are divided into two sessions, pre- labs and in-labs . All pre-lab sessions are done in one week while all in-lab sessions are done live/ synchronously on Zoom during your lab session in the week following the pre-lab week. You are expected to spend an equal amount of time on both parts. During the pre-lab sessions, you will prepare for the activities in the in-lab sessions by reading the experiment in this lab manual and reading various On-Line Introductory Materials . You will complete an online Canvas pre-lab quiz. You will then use the knowledge gained to answer questions about the experiment and the procedure for the experiment. You will answer the questions in canvas quiz with multiple choice questions or write free-form in the canvas site. Details of the submissions will be provided online. Pre-Lab Week Sessions Most of the experiments are designed with just enough guidance to allow you to make your own discoveries. Laboratory your lab report Assessment form (this is equivalent). During the in-lab session, you will perform the experiment using techniques you read about and following the procedure that you designed during the preceding pre-lab session. You will complete this by attending the in-lab Zoom session and answering questions with iclicker, H5P assessments and poll questions. Once completed, you will submit the In-Lab Week Sessions

3 The laboratory grades are based on your pre-laboratory submissions, data analysis, Lab Reports discussion answers, and online assignments/ quizzes. Detailed marking schemes are included with each experiment. Overall distribution of marks will be provided towards the end of the term. 6. Experimental Design Form This lab manual does not provide easy-to-follow step-by-step procedures for each experiment. Such an approach is known as the “cookbook” method of teaching chemistry and in the Chemistry 154 laboratory program this has been replaced by an “inquiry-based” approach to lab teaching. Using this method, students are provided with the necessary background information on concepts and techniques, and then are required to piece this information together to devise a procedure that can be followed to achieve the goal of the experiment. Accordingly, in Chem 154, you must design your own procedure for each experiment. To assist you in this task, there is a considerable amount of On-Line Introductory Material available for you to review. 7. Assignments and On-Line Introductory Materials Each experiment has a lab manual with relevant material that should be reviewed. The on-line introductory materials are accessed through Chemistry 154 Laboratory Canvas . You will be directed to all of the various techniques associated with each experiment. On-Line Introductory Materials: Technique Tutorials These are tutorials that teach you about various lab techniques, chemical concepts, and calculation methods that you will be using in a particular experiment. Most of these modules contain color slide- shows that demonstrate how to use the same equipment found in the Chem 154 labs. 8. Concept Mapping A concept map consists of at least two concepts linked by their relationship: Concept rel ationship The most important part of the concept map is found in the relationship, expressed using single words or phrases that generally contain a verb. The link can be established in any direction, but often there is a hierarchical or tree-like structure to their form. For each experiment, and prior to coming to the online lab session, complete the pre-lab assessments which might involve answering online canvas quizzes and filling out the Experimental Design Form (EDF) found under the online module for each experiment. F o r t h e E D F , use a point-form style that you can easily follow while in the lab during the In- Lab Week. Your EDF submissions are checked by your teaching assistant (TA) before the beginning of the In- lab session. This form is worth marks. If your TA finds many inconsistencies in your pre-lab work and others in the course, these will be discussed with all the students during the lab session. Late submissions for pre-lab work are only accepted for a short time period.

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4 Why Concept Mapping? Concept mapping helps you integrate and remember course material. In university you need to understand bits of information (facts, chemical symbols, etc.) as well as how these bits of information fit together to form concepts. Concept maps help you establish connections between concepts. Naming the type of relationship you have created tests whether you understand how the concepts fit together. The concept map on the right summarizes the analytical methods that will be introduced throughout the Chem 154 laboratory.

5 9. Writing a Lab Report: Each experiment in Chem 154 (except the WebMO exercise) consist of many assessments – pre-lab work, in-lab questions and post lab analysis/ assessment that need to be uploaded/ answered on the Canvas page – these could be canvas quizzes, online written assessments, iclicker questions, H5P assessments and poll questions from zoom and the Post-Lab Analysis (PLA) Sheet for each experiment. A Cover Page is included in each experiment which provides a marking scheme that your TA uses to grade your Lab Report and a Concept Map overleaf. All students need to complete the pre-lab work prior to the in-lab session. The relevant part of the submission will be discussed by the instructor/ teaching assistant during the in-lab session. Feedback is provided on marked pre-lab work and PLAs within a week of you completing an experiment. You should use the feedback to improve your performance on the next lab/ experiment. 10. Laboratory Instruction The laboratory manual describes background theory, as well as the equipment and procedures used in each of the experiments of the course. Please go over the contents and layout of the manual before reading the experiments. In particular, it is very important to read the first few introductory pages (as you are doing right now), which include policies and general information. You'll get further details about the experiments in an introductory talk given by your lab director, Dr. Monga, before the lab commences. These talks include important information about procedures and safety; therefore, it is important that you be on time for your laboratory periods. All TAs are graduate students in the Chemistry Department and are actively involved with their own research and/or course work. TAs will not be available outside of laboratory times to answer questions. For out-of-lab help go to the Discussion tool on Canvas or email Dr. Monga. 11. Other Information for Chem 154 Labs • You need a CWL account to access Canvas for some of the laboratory's online course requirements. Proper internet connection and access to use online tools such as H5P assessments and videos should be permitted by your browser. It is your responsibility to check compatibility issues before the first in-lab session. • Wearing eye protection and a lab coat is mandatory in the lab . But for Chem 154, you will be doing all the work online. Therefore you do NOT need to purchase any lab related protective gear (e.g. lab coats and safety glasses). • Laboratory notebooks are not required. • Requirements for each week are specified in your schedule. • The lab mark constitutes 15% of the overall course mark. A mark distribution summary is printed inside the front cover of this manual. Details are included with each experiment. • Please email freshman154@chem.ubc.ca if you have any laboratory related problems, for a missed session or for arranging make-up labs. Do not send messages using the canvas mailing system. That inbox is unmonitored. • In-lab sessions: Attendance for students will be checked within the first few minutes of the session through the use of iclicker questions. It is your responsibility to make sure that iclicker, zoom and canvas quizzes are operational on your device. If you get disconnected or are unable to join the session for some reason, inform the instructor immediately. • iClickers during the lab sessions will be posted randomly during the lab session. You will be awarded grades for attempting these questions, not for getting the correct answer. So please answer all iclickers. If you were unable to answer one of the questions due to connectivity issues, email the instructor to inform them.

6 • Online assessments – All online assessments (.pdf submissions, quizzes or discussion questions) are posted with an availability date and due date. There will be a 10% penalty for each day for each assessment that is submitted late. It is YOUR responsibility to ensure that you are uploading the correct file and you check your grades for the assessments periodically as well. For example, if you reach out to the instructor in November about an incorrect file uploaded in September, the submission will not be accepted. • Uninformed missed attendance will be considered as a missed lab and in-lab session grades will not be awarded. • GRADES on Canvas – online quizzes, pdf submissions and attempting H5P assessments. These will be available in the gradesbook on canvas. However, grades for attempting the iclicker questions will not be processed in the canvas gradebook. You will need to look at your grades in the iclicker account to see the missed assessments. 12. Procedure for Making up a Missed Lab Students are required to complete all of the experiments in their schedule. If a student misses an experiment, he/she is responsible for arranging a make-up session. If a missed experiment is not made up, a mark of zero is assigned for that experiment. • Missed labs are made-up during the regular lab sessions. ***** Make sure you check your schedule. A make-up lab for preparing for the wrong experiment or submitting the wrong file carries a marks penalty ***** To arrange the make–up: As soon as you know you are going to be absent, contact freshman154@chem.ubc.ca to arrange your make-up session. Your TA is unable, and not permitted, to schedule make-ups for students. • A make-up session is only permitted under special circumstances (i.e. things outside of your control, such as medical emergencies); writing a midterm on a lab day, social obligations or poor scheduling are not considered special circumstances. You may be asked to provide supporting documentation for the absence (e.g. a doctor’s note). If a missed experiment is not made up, a mark of zero is assigned for that experiment. • Only one make-up session is permitted unless there are extenuating circumstances. During the make-up session: Complete your experiment and ensure that your post-lab assessment is completed before the new due date set by your instructor for you.

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7 13. Safety in the Lab P ERSONAL P ROTECTIVE E QUIPMENT (PPE) IN THE C HEMISTRY L ABORATORIES AT UBC Eye Protection in the Lab We do not have the privilege of deciding when eye protection is or is not necessary - this question has already been decided by the senior administration at this university. Students who do not wear eye protection at ALL times in the chemistry laboratory will be asked to leave the laboratory and a mark of zero will be given for the experiment they were performing. Students should provide their own eye protection. The Chemistry Department sells both regular and over the glass’s safety glasses. If you forget your safety glasses, they can be rented in the lab for $1 per lab. Contact lenses are not recommended in the laboratory. If you do have to wear contact lenses then follow point (i) below. Clothing Protection in the Lab Students must wear a long, 100% cotton lab coat at all times when in the chemistry laboratory. Students who do not wear a lab coat will be asked to leave the laboratory and a mark of zero will be given for the experiment they are performing . Suitable lab coats can be purchased from the Chemistry Department. A very limited number of lab coats are available for rental in the lab for $2 per lab. In addition to wearing a lab coats, students must wear: • long pants – no shorts, skirts, capris, three quarter length pants or nylons. • socks and closed toed shoes There should be no exposed skin on your legs and feet at all. The following is the Standard Policy for all Chemistry Laboratory Courses at UBC: Adequate eye protection is required for all individuals working in the laboratory. Do not remove your eye protection until you have physically left the laboratory . The following types of eye protection are acceptable. (i) If you DO NOT wear prescription glasses, safety glasses must be: • Shatterproof • Have side shields • Be close fitting to your face (ii) If you DO wear prescription glasses, safety glasses must be: • Shatterproof • Have side shields • Fit over your prescription glasses Note: students may wear safety goggles but they are uncomfortable and steam up in the lab

8 Accidents: Accident procedures are posted in every laboratory for the specific guidance of responsible persons. All injuries, trivial or not, must be reported immediately to your teaching assistant and lab supervisor. Equipment: Every student is expected to clean his/her own equipment, replace broken items from the storeroom, and dispose of waste materials in the designated places. In particular, waste paper, waste glass and waste chemicals are collected in separate containers. Good housekeeping in the laboratory is the key step toward acceptable safety practices. Neither students nor staff are expected to work in a hazardous setting; consequently, any student who behaves irresponsibly will be expelled from the laboratory to ensure the minimum risk to all persons. STUDENTS MUST WEAR EYE PROTECTION and LAB COATS AT ALL TIMES IN THE LABORATORY.

9 Hazard Symbols: The following three hazard symbols or phrases are the most common ones that you may find on chemicals used in this laboratory. It is very important that you understand what these terms mean and how you should handle a chemical with this particular hazard. SYMBOL EXPLANATION PRECAUTIONS Combustible & Flammable -is one that will burn and therefore a potential fire hazard - may burn at relatively low temperatures; flammable materials catch fire at lower temperatures than combustible materials -may burst into flames spontaneously in air or release a flammable gas on contact with warm water - may cause a fire when exposed to heat, sparks, or flames or as a result of friction - keep the material away from heat sources and other combustible materials -never smoke when working with or near the material Corrosive Material -causes severe eye and skin irritation upon contact -causes severe tissue damage with prolonged contact -may be harmful if inhaled -keep containers tightly closed -avoid skin and eye contact by wearing all necessary protective equipment including eye, face and hand protection and protective clothing -avoid inhaling by using in well ventilated area only and/or wearing the proper respiratory equipment Poisonous & infectious Material: Carcinogenic or Cancer Suspect -is a poisonous substance that is not immediately dangerous to health -may cause death or permanent damage as a result of repeated exposures over a long period of time -may be a skin or eye irritant -may be a sensitizer, which produces a chemical allergy -may cause cancer -may cause birth defects -avoid skin and eye contact by wearing all protective equipment and hand protection and protective clothing -avoid inhaling by working in well-ventilated areas and/or wearing respiratory equipment as designated by your supervisor -store the material in designated place only

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10 In chemistry, as in experimental sciences in general, numbers fall into 2 categories: measured and exact. In the chemistry laboratory measured numbers include those obtained when determining the mass of a compound or the volume of a solution. Characteristic of all measured values is the fact that there is some degree of uncertainty, or unreliability, associated with them. Exact numbers, on the other hand, are known with certainty. The following discussion is intended to serve as a guide for understanding, reporting and calculating numerical results. Measured numbers and significant figures Every observed measurement made is really an approximation. For example, the length of the object in Figure 1 is between 1.5 and 1.6 units. Its length is reported to be approximately 1.54 units. There is uncertainty in the last digit 4; it is estimated. Figure 1 In general, on a linear scale, the human eye is capable of estimating the position of a mark situated between two of the smallest divisions to the nearest one-fifth (1/5 th = 0.2) of the smallest division. Thus in the diagram above, the smallest division is imagined to be divided into five equal sections and, as a result, the edge of the grey object is estimated to be at the second of these sections. Since each section is 0.2 of the smallest division it is equal to 0.04 units and the length of the object is reported to be 1.54 units. When a measured quantity is given as a digital readout which does not fluctuate, uncertainty still exists in the measurement. For example, when a digital balance indicates the mass of an object as 2.6 grams, there is uncertainty in the 6. When recording a measurement, it is the last digit that represents some degree of uncertainty and, in the case of our example, this means that the object was weighed to the nearest tenth (0.1) of a gram and that its exact mass is between 2.5 g and 2.7 g. We say the number 2.6 g contains two significant figures, the numbers 2 and 6 being the significant figures. If the recorded mass of the object were 2.633 g, there are four significant figures (2, 6, 3, and 3) and it means that the object was weighed to the nearest thousandth (0.001 g) of a gram. Thus, it is the last (underscored) 3 that has been estimated. Significant figures refer to those digits we know with certainty plus the first doubtful or estimated digit. Leading zeros in a number are not significant and trailing zeros are significant only if the number contains a decimal point. The volume 0.0178 L exhibits three significant figures, and the volume 250.0 mL exhibits four significant figures. In both cases the volume was measured to the nearest 0.1 mL. The volume 250 mL has two significant figures and implies an error of ± 10 mL. If one measured 250 mL to the nearest millilitre, the volume should be reported as 0.250 L. All fractional numbers are written with a zero before the decimal point (0.50 g and not .50 g) as a safety precaution against the possible misprint of the decimal point. Thus, if the decimal point fails to print, 0.50 g would read 0 50 g, clearly indicating a missing decimal point, while .50 g would read 50 g. 14. Significant Figures

11 Your data record must always include the correct number of significant figures required to indicate the precision of the apparatus used in the experiment. As well, subsequent calculations must be completed using the correct number of significant figures. Significant figures and calculations In any calculation in which experimental results are used, the final result should contain only as many significant figures as are justified by the experiment. Thus, the least precise measurement dictates the number of significant figures that should be present in the final answer. To reduce round-off errors in a sequence of calculations, the individual steps of the complete calculation are performed with one more figure than is significant. Thus, if the least significant data are observed to four significant figures, the calculations have to be carried out using at least five figures. The resultant final value, however, is precise to only four figures and must be recorded with four significant figures. 1. Addition and Subtraction . In addition and subtraction, retain only as many decimal places in the results as there are in that component with the least number of decimal places. i.e. 121.1 + 2.035 + 6.12 = 129.255 Becomes 129.3 2. Multiplication and Division . In multiplication and division the answer should contain only as many significant figures as are contained in the factor with the least number of significant figures. i.e. 21.71 x 0.029 x 89.2 = 56.159428 Becomes 56 The number 0.029 contains only two significant figures; therefore, according to the rule above, the answer should be rounded off to contain two significant figures: 56. 3. Logarithms and antilogarithms . The number of significant figures usually, but not always, changes when the logarithm or antilogarithm of a number is taken. This is due to the nature of the function and is best illustrated by example. In general log 10 (x) = y where x has n significant figures, ln(x) = y y has n + 1 significant figures e.g. log 10 2620 = 3.418 log 10 2.62 x10 3 = log 10 2.62 + log 10 10 3 = 0.418 + 3 (integer) and in general e x or 10 x = y x has m significant figures y has m-1 significant figures e.g. 10 3.418 = 2.62 × 10 3 or 10 0.418 × 10 3 = 2.62 × 10 3 Example Consider the following laboratory problem as a typical example and review of the usage of significant figures. Please note that we retain one extra digit until the last calculation. This digit should be retained in the calculator and does not need to be recorded.

12 5.1144 g of potassium hydrogen phthalate, a primary standard monoprotic acid with the formula KH 5 C 8 O 4 was dissolved in sufficient water to make 250.0 mL of solution. 25.00 mL of this acid required 25.06 mL of sodium hydroxide solution for neutralization. What is the molarity of the acid and the base? • Calculate and record the formula weight to five significant figures. 39.0983 + 5x1.0079 + 8×12.011 + 4×15.9994 = 204.22 g/mol It is important to realize that a slightly incorrect value for the formula weight will be obtained if the atomic weights are rounded to the first decimal place before summing them. i.e. 39.1 + 5 × 1.0 + 8 × 12.0 + 4 × 16.0 = 204.1 • Calculate and record the moles of acid to five significant figures to reflect the precision of the mass. millimoles of acid = 5114.4 mg/204.22 (g/mol) = 25.044 mmol • Calculate the molarity of the acid using five figures but only record the four significant figures. molarity of the acid = 25.044 mmol/250.0 mL = 0.1002 mol/L The five figure result 0.10018 should be retained in your calculator for subsequent calculations. • Calculate the molarity of the base using five figures, but again record only the four significant ones. molarity of the base = 0.10018 × 25.00/25.06 = 0.09994 mol/L The molarities are recorded to four significant figures because the least precise number used in the calculations (volumetric data) exhibits only four significant figures. Exact numbers As noted above, exact numbers are known with certainty. Exact numbers are numbers that are not measured experimentally and include defined conversion factors such as 1 mL = 1/1000 L (there are exactly 1000 mL in 1 Litre, by definition), 1 kg = 1000 g or 1 minute = 60 seconds. Counting numbers, such as the number of samples tested in an experiment, are also exact numbers. Exact numbers are exact, not estimated, and therefore have no uncertainty associated with them. They are said to contain an infinite number of significant figures and thus in a calculation have no effect on the final result. 15. Precision and Accuracy Essential to quantitative scientific measurement is an understanding of how reliable a measurement is. Precision and accuracy are two terms related to a measurement’s reliability. Only a brief consideration of their meaning will be given here. Precision refers to the consistency of measurements with each other; in other words precision describes the reproducibility of a result. If a quantity is measured several times and the values agree closely with each other, the measurement is precise. If the values differ widely, the measurement is not very precise. Poor precision is often a result of poor technical skills. Accuracy describes how close a measurement is to the true, or known, value. It is possible to have a series of reproducible measurements which are incorrect – precision is good and accuracy is poor. It is also possible to have a series of very poorly reproduced measurements which average around the correct value – precision is poor and accuracy is good. Ideally a procedure is both precise and accurate. In terms of the equipment used in the laboratory, more precise equipment provides measurements containing a greater number of significant figures. If this laboratory equipment is both properly calibrated and correctly used, the result will also be more accurate.

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13 16. Errors Types of errors Two types of errors, random and systematic, contribute to a measurement’s uncertainty. Systematic errors stem from flaws in the equipment or design of the experiment. If this is the case and an experiment is conducted with the same equipment in the same way, the error is reproducible and the results are precise but inaccurate. Theoretically, systematic errors can be determined and corrected. Poor accuracy is associated with systematic errors. Random errors are those errors over which the experimenter has little or no control. Random errors are always present and they have an equal chance of being either positive or negative. Measuring the mass of the same object on the same analytical balance three times and obtaining 3 different masses that differ by 0.0002 g is due to the internal balance mechanism and is an example of a random error. Random errors can never be completely eliminated. Random errors are associated with poor precision. Please note that in your lab reports error discussions should only refer to systematic and random errors. Mistakes, or human errors, such as spilling solutions, using the wrong solution, forgetting to take a reading, using dirty glassware, incorrectly using the balance, or making calculation errors, all of which can be corrected by doing the step over, are not valid experimental errors. These mistakes should be included in the observations portion of your Design Form and every attempt should be made to correct the mistake; time permitting, you may be required to start over. 17. The International System of Units The International System of Units (SI) is a rationalized and coherent system of units based on the metre, kilogram, second, kelvin, ampere, mole, and candela. It was proclaimed for use in Canada on August 1, 1974. Quantity Name of Unit Symbol Definition length Metre m (lower case) * weight Kilogram kg (lower case) * time Second s (lower case) * temperature Kelvin K (upper case) * volume Litre L (upper case) 10 - 3 m 3 kg . m/s 2 kg/m . s 2 kg . m 2 /s 2 amount mole mol (lower case) * concentration molarity M (upper case) mol/L * Fundamental basis of International System of Units force newton N (upper case) pressure pascal Pa energy joule J (upper case)