Chem 161: General Chemistry 1 Lecture 1 Chapter E Part 1 PDF

CHEM 161: General Chemistry 1 Dr. S. Sahni [email protected] [email protected] Sections 31-43 Lecture: Mon, Wed 7:30-8:50 pm (Beck Aud) Office Hours: Wed 6:00-7:00 pm (Beck 006) Thurs 12:00-1:00 pm (CCB B204)  Textbook...

CHEM 161: General Chemistry 1 Dr. S. Sahni [email protected] [email protected] Sections 31-43 Lecture: Mon, Wed 7:30-8:50 pm (Beck Aud) Office Hours: Wed 6:00-7:00 pm (Beck 006) Thurs 12:00-1:00 pm (CCB B204)  Textbook “Chemistry: Structure and Properties”, Third Edition, by Nivaldo Tro. The e-book is available First Day Course Materials, found in the left-hand column. $39.00 cost is included in tuition bill. You can opt out if you want by Sept 17th Recitations ❖ Smaller problem-solving sessions 55 minutes long ❖ It’s your chance to ask questions! ❖ Recitation sections will either be in-person or online. ❖ Attendance and participation (by answering quiz or poll questions) in recitation is mandatory and will count towards the final grade.  Exams and Grading Percentage of total grade Three Midterm Exams 42 % (3 x 14) Final Exam 28% Online Homework Quizzes 20% (see note on syllabus) Recitation 5% Surveys 5% Total 100% A (≥ 90%); B (75-89%); C (55-74%); D (45-54%); F (< 45%). Exam 1 Tuesday evening, October 1 7:45 pm - 9:05 pm Exam 2 Wednesday evening, October 30 7:45 pm - 9:05 pm Exam 3 Wednesday evening, December 4 7:45 pm - 9:05 pm Final Exam Tuesday afternoon, December 18 4:00 pm to 7:00 pm Exam conflict: contact the course administrator at [email protected] A detailed syllabus is available on Canvas  Graded Homework: Online on elearning https://classroom.elearning.rutgers.edu There are two type of assignments: 1. A nongraded practice assignment - do BEFORE the quiz. 2. A graded and timed assignments/quiz divided into 2 parts Quiz 1: Released on Wednesday Quiz 2: Released on Friday Both are due every Monday 6:00 PM ONE ATTEMPT to complete each part of the quiz and once you start, and you have to complete it within 25 minutes. The sum of the scores of both quizzes will be used to calculate the weekly quiz score. 2 lowest quiz scores will be dropped. If a quiz is missed, this will count towards one of the lowest scored quizzes, so extensions and/or make-up will not be granted. Technical issues report to : https://techsupport.elearning.rutgers.edu.  Tips for Success 1. Attend Lectures, Recitations, Office hours…. Read material ahead of class. 2. Strive to have an in-depth understanding of the material 3. Work through the problems…Group work is great! This course moves very fast! Material is more difficult than high school. Exam are more challenging! 4. Time management is key: Set aside time in your schedule to dedicate to Chemistry. 5. Don’t procrastinate! DO NOT wait until exam week to start studying!! 6. Get help! Don’t be shy! You can attend any office hours and study sessions. Complete list is on canvas.  Active Learning Workshops What are they? ALWs aim to guide students to develop a deep understanding of important course content via collaborative, active problem solving. These sessions will replace your weekly recitation. How to sign up? https://rutgers.ca1.qualtrics.com/jfe/form/SV_5teWS pJ9ULyFlmCLinks to an external site.  Active Learning Sections (in place of your regular recitation) Instructors: Dr. Francesca Guerra, Dr. Christine Altinis-Kiraz, Dr. Marc Muñiz Meeting Times in person start 9/19/23 Tuesday: 10:20 AM - 11:40 AM in AB 4400 (College Ave. Academic Building East) Tuesday: 12:10-1:30 PM in AB 4400 (College Ave. Academic Building East Teaching Interns (TIs): undergraduates who have been successful in Gen. Chem. at Rutgers and are trained by the instructors to help guide students during the workshops toward building greater mastery of the concepts and skills necessary for success in Chem 161 and beyond. https://dcs.rutgers.edu/classrooms/active-learning-spaces  Additional Help from Teaching Interns Teaching Interns (TIs) are undergraduate students who successfully completed general chemistry courses and are eager to help you succeed as well. TIs will be holding the following help sessions for you this semester: – Online Office Hours: An opportunity to ask questions, discuss new concepts or get help on how to solve problems. – Problem-Solving Sessions: Focus on refining your understanding of concepts and enhancing your problem-solving techniques. – Exams Review Sections: Held for about two hours before each exam to practice exam-style questions. TIs will begin their sessions in Week 3. Look for the announcements on Canvas!  Chapter E Essentials: Units, Measurements, and Problem Solving  Macroscale, Microscale, and Nanoscale In science we need to make REALLY BIG and really small measurements…. © Pearson Education, Inc. Measured Quantity Standard Number Scientific Notation Diameter of Earth 12,800,000 m 1.28 x 107m Length of a pox virus 0.0000003 m 3 x 10-7 m -7 is the power of 10 Coefficient (number between © Dr S. Sahni 1-9) -7 is called: exponent  Units of Measurement English System of Units of Metric/International System (SI) of Units mile → yards → feet → inches kilometer (km) → meter (m) → centimeter (cm) Conversions: 1 mi = 1760 yd Conversions: 1 km = 103 m 1 yd = 3 ft 1 m = 102 cm 1 ft = 12 in 3.440 mile = 6060 yards = 18,176 feet 5.54 km = 5.54 x 103 m = 5.54 x 105 cm © Dr S. Sahni  SI Units of Measurement The 7 fundamental units of Measurement SI (Système International): Official system of measurement throughout the world Base Units of the SI System Property Measured Name of Unit Symbol of Unit Units for smaller or larger measurements length meter m involve prefixes which mass kilogram kg are powers of 10. time second s temperature kelvin K amount of substance mole mol electric current ampere A luminous intensity candela cd All other units are Derived from these seven units. © Dr S. Sahni Metric and SI system: Prefixes : memorize I will use these equalities in unit conversion problems 1 Gm = 109m 1 Gm = 109m 1 Mm = 106 m 1 Mm = 106 m 1 km = 103 m 1 km = 1000 m = 103 m base unit meter (m) or liter(L) or gram (g) base unit(m) base unit meter (m) 1 dm = 10-1 m 1m = 10 dm (decimeter) 1 cm = 10-2 m 1m = 100 cm (centimeter) 1 mm = 10-3 m 1m = 1000 mm (millimeter) 1 m = 10-6 m 1m = 106 m (micrometer) 1 nm = 10-9 m 1m = 109 nm (nanometer) 1 pm = 10-12 m 1m = 1012pm (picometer) © Dr S. Sahni Metric and SI system Prefixes to Memorize Two ways to write the equalities: 1 Gm = 109m 1 Gm = 109m 1 Mm = 106 m 1 Mm = 106 m 1 km = 103 m 1 km = 1000 m = 103 m base unit(m) base unit meter (m) 1 dm = 10-1 m 1m = 10 dm (decimeter) 1 cm = 10-2 m 1m = 100 cm (centimeter) 1 mm = 10-3 m 1m = 1000 mm (millimeter) 1 m = 10-6 m 1m = 106 m (micrometer) 1 nm = 10-9 m 1m = 109 nm (nanometer) 1 pm = 10-12 m 1m = 1012pm (picometer) © Dr S. Sahni  Length Mass  SI unit : meters (m). The mass of an object is a measure of the  1 meter is defined as the quantity of material it contains. distance light travels in a  SI unit : kilogram (kg) vacuum during a time interval  1 kg is defined based on Plank’s Constant of 1/299,792,458 of a second Weight (different from mass) is a measure of the gravitational pull on the object. A nickel weighs about -5 g on earth -0.833 g on the moon Mass is an Extensive physical property; it is dependent of the amount of substance being measured. © Dr S. Sahni  Temperature Scales: SI base unit = Kelvin The temperature of a sample of matter is a measure of the amount of average kinetic energy—the energy due to motion—of the atoms or molecules that compose the matter. Celsius to Fahrenheit Water Boils TF =1.8 (TC)+32 Fahrenheit to Celsius Normal Body Temperature TC =TF - 32 Water 1.8 Freezes Celsius to Kelvin KELVIN CELSIUS FAHRENHEIT TK = TC + 273.15 Absolute temperature = 0 K; It is theoretically the lowest possible temperature possible where all atomic motion ceases. © Dr S. Sahni  Boomerang Nebula Is Colder Than Space Itself Bill Saxton/NRAO/AUI/NSF/NASA/Hubble/Raghvendra Sahai https://www.sciencealert.com/ Some 5,000 light-years from Earth, there's a bizarre and mysterious nebula that clocks an average temperature of just 1 Kelvin (−272.15 °C or −457.87 °F), making it the coldest natural object in the known Universe. © Dr S. Sahni  Volume (derived unit) Volume is the space occupied by a substance. Its units are (unit of length)3 :  1) (cubic meter) m3 in the SI system. (it is a derived unit)  2) liters (L) and milliliters (mL) by chemists. (more commonly used) 10 cm=1 dm Volume of small cube= 1 cm x 1 cm x 1 cm = 1 cm3 = 1 mL 10 cm=1 dm Volume of big cube = 10 cm x 10 cm x 10 cm =1000 cm3 = 1L 1 L = 1000 mL Volume= 1 dm x 1 dm x 1 dm= 1 dm3 = 1L 1 L = 1.057 qt 1.0 mL =1.0 cm3 = 1 cc 1 L = 1000 mL 946.3 mL = 1 qt © Dr S. Sahni  Density Density is defined as mass per unit volume density = mass or d = m volume v SI Units: kg/m3 Common Units: g/mL for liquids, Objects that are more dense g/cm3 for solids than water will sink in water Density is an Intensive physical property; it is independent of the amount of substance being measured. Density can be used to identify a compound. Density can be used as a conversion factor to convert mass to volume or volume to mass ……(more detail later) © Dr S. Sahni  Energy Energy is defined as the capacity to do work. Work is defined as the action of force through a distance Energy = Force x Distance = mass (kg) x acceleration (m/s2) x distance (m) Units of density: SI unit : kg m2 /s2 defined as a Joule (J) Common unit: calorie (cal) or Calorie (Cal) 1 calorie = 4.184 joules Law of conservation of energy: Energy is neither created nor destroyed but converted from one form to another. Living organisms undergo cellular respiration to convert the potential energy in sugars into kinetic energy for their use. C6H12O6 + O2 → 6CO2 + 6H2O + energy https://www.sciencebuddies.org / © Dr S. Sahni  Some Common Units and Their Conversions Table E3 Common Equalities (these will be given) Metric prefixes/ conversions must be memorized  Exact Numbers Measured Numbers An exact number is obtained A measuring tool is used to determine a ❖when objects are counted quantity such as the length or the mass of an object For example 2 baseballs 4 pizzas ❖or from defined quantities 9.14 cm All measurements have For example: ❖ certain digits 1 foot = 12 inches ❖ uncertainty 1 meter = 100 cm (estimated or last digit) ❖ units © Dr S. Sahni  Uncertainty or Reliability of a Measurement Uncertainty of a measurement is ±1 in the last digit reported ❖ Cosmotologists report the age of the Universe as 13.7 billion years Uncertainty = ±0.1 billion years = ± 100 million years ❖ In the 2024 Olympics, Noah Lyles (USA) ran the 100 m race in 9.784 seconds Uncertainty = ±0.001 seconds He beat Jamaica’s Kishane Thompson (9.789 seconds) by five-thousandths of a second. © Dr S. Sahni https://abcnews.go.com/ Reporting Measured Numbers 1 cm smallest scale division= _______ 4 reading is between ___cm 5 and __cm 4.2 length is reported as __________cm 2 estimated digit is _________ error in the measurement is± 0.1 cm ________ smallest scale division = _______ reading is between ______cm and ___cm length is reported as ___________cm estimated digit is _______ error in the measurement is _________ © Dr S. Sahni  Volume Measurement ❖ Examine the scale of the measuring cylinder. ❖ Take the reading of the bottom of the meniscus a) 4 mL b) 4.5 mL c) 4.55 mL d) 4.555 mL © Dr S. Sahni  Significant Figures in Measurements ❖ A scientific measurement is made up of all the certain numbers in a measurement plus the one uncertain digit ❖ All these digits make up the significant figures of that measurement. ❖ The significant figures reflect the precision of the instruments used to make that measurement ❖ Greater the number of significant figures, more ‘certain’ or precise is the measurement. © Dr S. Sahni  Significant Figures (sig figs or sf) ❖ All non-zero digits are significant. 3.9 2 sig figs ❖ Interior zeroes between two non-zero 3.09 3 sig figs numbers are significant ❖ Leading zeroes before a number are 0.0000309 place holder and are NOT significant leading zeroes 3 sig figs not significant These trailing ❖ Trailing zeroes are 54.0 540350 zeroes are place -significant if there is a decimal 3 sig figs 5 sig figs holders and are -ambiguous if they are before an implied 6000 not significant decimal and are not significant 1 sf ❖ Numbers in scientific notation 5.8040 x 10-4 Powers of 10 are © Dr S. Sahni 5 significant figures not significant How many measurements below contain three significant figures? i) 0.4760 ii) 0.476 iii) 4.76 x 103 iv) 150,000 vi) 220.00 ii) 0.00150 a) 1 b) 2 c) 3 d) 4 e) 5  Rounding In calculations, calculated answers are usually rounded off to obtain the correct number of significant figures. Round only at the end of the problem !!! Identify the digits to keep, identify the digit to be dropped Rules of Rounding: If dropped digit < 5, round down; If dropped digit > 5 round up; If dropped digit = 5 round up Round the following to 3 significant figures: Round to 2 significant figures: dropped digit A. 5.3465 m 5.35 m ______ A. 5.3465 m ______ B. 12.999 L ______ B. 12.999 L ______ © Dr S. Sahni Significant Figures in Calculations The type of glassware used to measure a volume directly affects the precision of the measurement. The significant figures of your measurements depends on the instrument used. The measurements are then used in calculations When doing a calculation, the number of significant figures in the answer is determined by the number of significant figures in the measurements For multistep calculations round at the very end of the calculation. There are separate rules depending on whether we are multiplying /dividing or adding/ subtracting measurements. © Dr S. Sahni  Significant Figures in Calculations: Multiplication and Division When multiplying or dividing numbers, the answer is rounded off to have the same number of significant figures as the measurement with the least number of significant figures 3 sf 2 sf ruler A measures Area = length x width = 5.76 cm x 4.8 cm 5.76 cm Calculator answer = 27.648 cm2 ruler B measures Does not reflect Round calculator answer 4.8 cm the precision of to 2 sf the measurements Answer = 28 cm2 © Dr S. Sahni  Significant Figures in Calculations: Addition and Subtraction ❖ When adding or subtracting numbers, the answer is rounded to the number of decimal places as the measurement with the least decimal places. ❖ If a number does not have a decimal, the answer is rounded off to the least certain digit. 3.90cm + 345.1 cm + 5.678 cm 3.90cm + 340 cm + 5.678 cm Underline the least Line up the 3.9 0 certain digits in all the 3.90 numbers and draw 345.1 34 0 measurements. a line after the least certain digit. 5.6 78 Line up the numbers 5.678 354.6 78 and draw a line after 34 9.578 the least certain digit. keep drop keep drop Round to the least certain Round to ones place place. Add a place holder 354.7 cm ‘0’ (if necessary) 350 cm © Dr S. Sahni Perform each calculation to the correct number of significant figures. a. 1.10 × 0.5120 × 4.0015 ÷ 3.4555 b. 430 + 0.245 – 49.0 For problems involving all operations follow PEMDAS, keep track of sig figs by underlining, round at the end! c. 4.562 × 3.99870 ÷ (452.6755 – 452.33) 452.6755 452.33 = 4.562 x 3.99870 ÷ 0.3445 0.3445 4 sf 6 sf 2 sf 2 decimal places = 52.952306 Underline the least significant digit but do not round until the end = 53 (rounded to 2 sf) d. 14.84 × 0.55 – 5.01 Perform each calculation to the correct number of significant figures. e. (9.66×10–1) + (5.1×102) – 8.77 + 2.8 (8.333×10–2)(3.001) a) 2 x 103 b) 2.0 x 103 c) 2.00 x 103 d)2.000 x 103 e)2.0000 x 103  Problem Solving Dimensional Analysis Using Conversion Factors  Importance of Unit Conversion Mars Climate Orbiter: Robotic Space Probe launched in 1998 to study Martian climate and atmosphere. Orbiter approach to Mars was lower than anticipated altitude and it was destroyed by excess atmospheric stresses It disintegrated due to ground computer software error that produced output in non SI units! 125 million dollar loss © Dr S. Sahni  Unit Conversion using Dimensional Analysis Q Convert 1.76 yards to centimeter (cm) ( 1 m = 1.094 yd) 1. Given: 1.76 yards 2. Find: centimeter 3. Plan: yd → m → cm 4. What are the equalities? 1 m = 1.094 yd and 1 m = 100 cm 1𝑚 1.094 𝑦𝑑 1𝑚 100 𝑐𝑚 5. Conversion factors 1.094 𝑦𝑑 1𝑚 100 𝑐𝑚 1𝑚 1𝑚 100 𝑐𝑚 6. Set up the problem. 1.76 yd x x = 160.8775 cm 1.094 𝑦𝑑 1𝑚 7. Check significant figures with given quantity. 161 cm (3 sf) 8. Does the answer make sense? cm is a smaller unit. It makes sense that 161 cm = 1.76 yard © Dr S. Sahni Q67 Tro. A European automobile has a gas mileage of 17 km/L. is the gas mileage in miles per gallon. (1 km = 0.6124 mi)( 1 gal = 3.785 L)  Unit Conversions involving Units raised to a power Q Convert 3.75 cm → in (1 in = 2.54 cm) Q Convert 3.75 cm3 → in3 3 (1 in) 13 in3 3.75 cm3 = 3.75 cm3 x = 0.228839 in3 x 2.543cm3 (2.54 cm)3 3 sf = 0.229 in3 3 sf © Dr S. Sahni Q Indicate the unit that completes each of the following metric equalities. Use dimensional analysis 1 Gm 1 Mm = 109m = 106 m 1 km = 1000 m 1) 1,000,000 m = _____ base unit meter (m) 1m = 10 dm (a) 103 mm (b) 1000 km (c) 1000 dm (d) 103 Mm 1m = 100 cm 1m = 1000 mm 1m = 106 m 1m = 109 nm 1m = 1012pm 2) 0.01 m = _____ (a) 1 mm (b) 1 cm (c) 1 dm Q True of False. Use dimensional analysis. A) 39.5 nm = 3.95 x 10-10 m B) 0.00000498 m = 4.98 x 10-6 m C) 4.56 cm = 0.456 mm  Suggested HW Problems Tro 3rd Edition Chapter E: 19,21,23,25,27,29,33,35, 37,39,41,43,47,49,51, 65,67, 71, 73, 75,99,103