CHEM 1701 Week 8 Past Paper Fall 2024 PDF

CHEM 1701 – Week 8 Unit 7 – The Mole and Stoichiometry Resources: www.durhamcollege.ca/connect If you req...

CHEM 1701 – Week 8 Unit 7 – The Mole and Stoichiometry Resources: www.durhamcollege.ca/connect If you require this material in an alternative format, please email me anytime. A mole: more than just a cute furry creature… Videos and Resources Here is a list of videos and resources organized by learning objective. LO 7.1 (Mole Concept) Intro to Moles: https://youtu.be/wI56mHUDJgQ Mole vs. Molecule: https://youtu.be/2P--fRgdSF0 LO 7.2 (Molar Mass) Molar Mass (concept): https://youtu.be/hY7lzRBylSk Molar Mass (calculate): https://youtu.be/Qflq48Foh2w LO 7.3 (Mole Math) Grams to Moles (part 1): https://youtu.be/CMnkSb2YsXI?si=FmyEhLoAeq2jT3cU Grams to Moles (part 2): https://youtu.be/0RXB8xNmJNM?si=iUicShC4yTwbWYib Moles to Particles (part 1): https://youtu.be/HMAOrGpkTsQ?si=di4Tk7062v93vXqT Moles to Particles (part 2): https://youtu.be/kGNtnq0kGKk?si=RzNO-X5LunUgHnXw Warm-up In math class you learned how to write and interpret CONVERSION FACTORS. That work was important for the math we do in this unit. Let’s revisit how to turn equalities and equivalencies into conversion factors. LIFE EXAMPLES: In your mind, this reads 1.06 g = 1 mL 1.06 g/mL Equality: 1 case of beer = 24 bottles 1 dozen = 12 eggs the average density of blood Conversion factors: CHEMISTRY EXAMPLES: In your mind, this reads In your mind, this reads 18.02 g = 1 mole 44.01 g = 1 mole Equality: 1 mole = 6.02 × 10 23 particles 18.02 g/mole 44.01 g/mole Conversion factors: CHEM 1701 – Week 8  Counting Molecules LO 7.1 Define mole, state Avogadro's constant and write Avogadro's constant as a unit conversion factor HEALTH CONNECTION: When pharmacists and chemists are EXAMPLE: The recommended Tylenol dose is 500 mg which testing a new drug, they need to know how many molecules of has 2,000,000,000,000,000,000000 Tylenol molecules. the drug are required to cause a desired effect. This is how they in words, that’s “2 sextillion” determine the safe and effective dose of a drug. in scientific notation, that’s 2 × 10 21 molecules But there is a challenge. Drug molecules are tiny (smaller than cells) and even a small dose of a drug contains billions and billions and billions of molecules. Counting tiny molecules is tricky, but chemists and pharmacists need to count properly to Brand: Tylenol get the dose right. So how do we work with large amounts of Active ingredient: acetaminophen molecules in an easy way? Chemical formula: C8H9NO 2 How do you count large amounts? What words do you use? You use words to talk about amounts all the time. Here are some examples. Dr. Jessica Meir and Christina Koch, Indigenous musical artists the first all-female space walk “A Tribe Called Red” Word: a “pair” of astronauts Word: a “trio” of musicians Word: a “dozen” eggs Amount: 2 Amount: 3 Amount: 12 How do chemists count large amounts? What words do chemists use? Chemists use a special word to count huge amounts of molecules. The word is MOLE, it is a unit of measurement for counting huge amounts of atoms and molecules (i.e., the number of C 8H 9NO 2 molecules in 1 Tylenol pill). 1 MOLE has 602,000,000,000,000,000,000,000 things in it. In words, that’s 602 hexillion. Yikes. It’s not useful to write this number in expanded form. Instead, we write this number in scientific notation as 6.02 × 1023. This number is on your REFERENCE SHEET. MOLE is a UNIT OF MEASUREMENT Word: mole Amount: 602,000,000,000,000,000,000,000 or 6.02 × 1023 GOOD TO KNOW: 6.02 × 10 23 is called Avogadro’s Constant after Amedeo Avogadro who discovered it. It is represented as N A in mathematical formulas. If you see N A in a formula, use the number 6.02 × 1023. CHEM 1701 – Week 8  How Big Is a Mole? LO 7.1 Define mole, state Avogadro's constant and write Avogadro's constant as a unit conversion factor Think of it like this… Visualize it like this… But atoms and molecules are tiny… A mole of atoms or molecules sounds like a lot but remember that atoms and molecules are tiny and don’t take up that much space. a bowl of jellybeans Atoms and molecules are much, much smaller than jellybeans, so If you have a DOZEN jellybeans, you have 12 jellybeans 6.02 × 10 23 atoms or molecules isn’t 6.02 × 10 23 jellybeans is that much. So small that they didn’t If you have a MOLE of jellybeans, you have as big as planet earth! even make the cut in this infographic. o 602,000,000,000,000,000,000,000 jellybeans o or 6.02 × 1023 jellybeans Visualizing 1 Mole of a Chemical The image below shows what 1 mole of different atoms and molecules looks like. The samples look like different amounts because the size of the atoms or molecules is different. DEMO: size of an H 2O molecule vs. C 6H 12O 6 molecule. KEY IDEAS: each sample has 6.02 × 10 23 “particles” so each sample is 1 mole the word particle is generic and is replaced with the word “atoms” or “molecules” depending on the sample 1 mole of sulfur atoms = 6.02 × 10 23 S atoms 1 mole of water molecules = 6.02 × 10 23 H 2O molecules 1 mole of sugar molecules = 6.02 × 10 23 C 6H 12O 6 molecules 1 mole of copper atoms 1 mole of mercury atoms = 6.02 × 10 23 Cu atoms = 6.02 × 10 23 Hg atoms SUMMARY: A mole is kind of like a dozen. There are 12 things in 1 dozen, and 602 hexillion things in 1 m_o_le. 602 hexillion written out is 6_0_2_,_0_0_0_,_0_0_0_,_0_0_0_,_0_0_0_,_0_0_0_,_0_0_0_,_0_0_0_(_6_0_2_+ 2_1_z_e_r_o_e_s_!). It’s not useful to write so many digits so instead chemists write this number in scientific notation as 6_._0_2_× 1023. This number is named after the scientist that discovered it and is called Avo_g_a_d_r_o_’s constant. 602 hexillion is a giant number, but atoms and molecules are so tiny/s_ma_ll that a mole of them isn’t that big. CHEM 1701 – Week 8  Avogadro’s Constant a Conversion Factor LO 7.1 Define mole, state Avogadro's constant and write Avogadro's constant as a unit conversion factor 1 mole = 6.02 × 10 23 is an EQUALITY so it can be written as 2 CONVERSION FACTORS. Revisit the warm-up activity on the first page for a conversion factor refresher. 1 mole = 6.02 × 1023 Conversion factor 1 Conversion factor 2 1 mole 6.02 × 1023 6.02 × 1023 1 mole 7.1 PRACTICE – Mole, Avogadro’s Constant and Conversion Factors 1) Refer to your formula sheet. Write the equality for Avogadro’s constant. 2) Write 2 conversion factors that can be written from the equality 1 mole = 6.02 × 1023 3) The unit that chemists use to measure large amounts of atoms and molecules is called the. One mole of a substance contains particles of the substance. 4) Write Avogadro’s constant in standard form (i.e., show all the zeroes). For example, 2.2 × 103 written in standard form is 2,200. 3) The word “particles” is as general term, a sort of placeholder. The word would be used if you were measuring something in atoms (i.e., C, Ne, Mg) and the word would be used I you were measuring something in molecules (i.e., CO2, C6H12O6). 4) Identify the following as an atom or molecule. O2 CO Ar Cu CuSO4 CHEM 1701 – Week 8  Molar Mass LO 8.2 Define molar mass, calculate the molar mass of elements and compounds, and write molar mass as a unit conversion factor Knowing the mass of 1 mole (or 6.02 × 10 23 particles) of a chemical is useful information. The mass of 1 mole of chemical is called MOLAR MASS. Molar mass represents how much 6.02 × 10 23 particles of an element weighs. Molar mass is on the periodic table. TASK: Look at the average atomic mass information on your periodic table. This is the mass of individual atoms in atomic mass units (u). This number is also the MOLAR MASS (g/mole) of the element. The molar mass can be written as a CONVERSION FACTOR 1 S atom 6.02 × 10 23 S atoms Molar mass: 32.07 g/mole Conversion Factors: 16 s S 32.07 g 1 mole or 1 mole 32.07 g sulfur 32.07 32.07 u 32.07 g AVERAGE ATOMIC MASS: MOLAR MASS: The mass of 1 sulfur The mass of 1 mole of sulfur atom is 32.07 u. atoms is 32.07 g/mole. 1 C atom 6.02 × 10 23 C atoms Molar Mass: 12.01 g/mole Conversion Factors: 6 c C 12.01 g or 1 mole 1 mole 12.01 g carbon 12.01 12.01 u 12.01 g AVERAGE ATOMIC MASS: MOLAR MASS: The mass of 1 carbon The mass of 1 mole of carbon atom is 12.01 u. atoms is 12.01 g/mole. PRACTICE: Use the periodic table to determine the molar mass for each element. Then write the molar mass as 2 conversion factors. Element Molar Mass Conversion factor 1 Conversion factor 2 iron 55.85 g/mole 55.85 g 1 mole 1 mole 55.85 g oxygen Cu nitrogen magnesium F CHEM 1701 – Week 8  Molar Mass of Molecules LO 8.2 Define molar mass, calculate the molar mass of elements and compounds, and write molar mass as a unit conversion factor The MOLAR MASS of a MOLECULE is found by adding up the molar masses of the elements in the chemical formula. Molar mass is always calculated for 1 molecule of a chemical only. This means you ignore any coefficients when calculating molar mass. HOW TO CALCULATE THE MOLAR MASS OF MOLECULES STEP 1: “BREAK IT DOWN” Use the CHEMICAL FORMULA and SUBSCRIPTS to find the AMOUNT of each atom. Use the PERIODIC TABLE to find the MOLAR MASS for EACH ELEMENT. STEP 2: “ADD IT UP” MULTIPLY and ADD it all together. Ignore coefficients when calculating molar mass NaCl 4 Al2O3 Ignore coefficients when H2O calculating molar mass 5 CO2 C6H12O6 Al2(PO4)3 CHEM 1701 – Week 8 8.2 PRACTICE – Molar Mass 1) TRUE or FALSE: The molar mass of water is 18.02 u. 2) Calculate the molar mass for each element or molecule. Write each molar mass as 2 conversion factors. Be thorough including all units and chemical formulas. g mole Chemical Molar mass 1st conversion factor: 2nd conversion factor: mole g Ca Cl2 S2Cl2 Ca3(PO3)2 Na2SO4 CuCl2 3) The reaction below is the process that turns glucose (C6H12O6) into energy. Calculate the molar mass for every chemical in the reaction. [TIP: Ignore coefficients when calculating molar mass. Molar mass is always calculated for 1 molecule of a chemical.] C6H12O6 + 6 O2 → 6 CO2 + 6 H2O C6H12O6 O2 CO2 H2O CHEM 1701 – Week 8  Mole Math LO 7.3 Perform calculations that convert between mass, moles and particles of a substance VISUALIZE IT: Below is a sample of water, H 2O. There are 3 different measurements we can take for same sample. The sample has: mass of 19.00 g 1.05 moles 6.35 × 10 23 individual H 2O molecules There are 3 different measurements we can take for the same sample of water The arrows and fractions are from the “mole roadmap” and tell us how to convert from one measurement to another.. MASS MOLES “PARTICLES” mole × 6.02 × 10 23 particles g × 1 mole g 1 mole × × mole 6.02 × 10 23 particles MOLE MATH is a set of calculations that allow us to covert between the mass, moles and “particles” of a chemical. To do “mole math” we use “mole tools” including: Avogadro’s constant (6.02 × 1023) molar mass (g/mole) the mole roadmap which tells us which conversion factor to use and when The “Mole Roadmap” molar mass as a conversion factor Avogadro’s constant as a conversion factor measurements CHEM 1701 – Week 8  Mole Math LO 7.3 Perform calculations that convert between mass, moles and particles of a substance HOW TO USE THE MOLE ROADMAP STEP 1: Determine the START and STOP units from the question. Find these units on the MOLE ROADMAP. STEP 2: Follow the ARROW between the units and note the CONVERSION FACTOR. Calculate MOLAR MASS if needed. STEP 3: ENTER DATA in the conversion factor and perform DIMENSIONAL ANALYSIS. Include the CHEMICAL FORMULA. STEP 4: SIMPLIFY, SOLVE and ROUND. EXAMPLE 1 (1-step calculation): 1 teaspoon of sugar has approximately 7.39 × 10 23 molecules C6H12O 6. What is this amount in moles? Round the answer to 2 decimal places. ANSWER ANALYSIS/SIDE WORK start: particles are given 1 mole (roadmap) particles × 7.39 × 10 23 molecules C6H12O 6 6.02 × 10 2 3 particles record the number stop: moles of particles from record Avogadro’s number as a fraction in this the question, orientation, include the include the chemical formula chemical formula unit remaining (enter data, 1 mole C6H12O6 dimensional analysis) 7.39 × 10 2 3 molecules C6H12O6 × 6.02 × 10 2 3 molecules C 6H 1 2 O6 unit cancels 7.39 × 1 0 23 × 1 (simplify) = 6.02 × 10 23 moles C6H12O6 unit (calculator) = 7.39E23 × 1 ÷ 6.02E23 moles C6H12O6 (solve) = 1.227574751 moles C6H12O6 (round) = 1.23 moles C6H12O6 (tie it together) 7.39 × 1023 molecules C6H12O6 is equal to 1.23 moles of C6H12O6. This amount of molecules and this amount of moles are the same amount of C6H12O6. CHEM 1701 – Week 8  Mole Math (1 conversion factor calculations) LO 7.3 Perform calculations that convert between mass, moles and particles of a substance EXAMPLE 2 (1-step calculation): What is the mass of 2.34 moles C 6H 12O 6? Round to 1 decimal place. ANSWER ANALYSIS/SIDE WORK start: moles (2.34 moles C6H12O 6) g (roadmap) moles × stop: mass mole record molar mass as a fraction in this calculate molar mass C6H12O 6: record the number of orientation, include the chemical formula = 6(12.01 g/mole) + 12(1.01 g/mole) moles from the + 6(16.00 g/mole) question, include the chemical formula = 180.18 g/mole unit remaining 180.18 g C6H12O6 (enter data, 2.34 moles C 6H 1 2 O6 × dimensional analysis) 1 mole C6H12O6 unit cancels 2.34 × 180.18 (simplify) = g C6H12O6 unit 1 (solve) = 421.6212 g C6H12O6 (round) = 421.6 g C6H12O6 2.34 moles C6H12O6 is equal to 421.6 g of C6H12O6. (tie it together) This mass and this number of moles are the same amount of C6H12O6. EXAMPLE 3 (1-step calculation): How many moles is 250 g C 6H 12O 6? Round to 1 decimal place. ANSWER ANALYSIS/SIDE WORK start: mass (250 g C6H12O 6) mole (roadmap) stop: moles mass × g record molar mass as a fraction in this calculate molar mass C6H12O 6: record the mass from orientation, include the = 6(12.01 g/mole) + 12(1.01 g/mole) the question, include chemical formula the chemical formula + 6(16.00 g/mole) = 180.18 g/mole (enter data, 1 mole C6H12O6 dimensional analysis) 250 g C6H12O6 × 180.18 g C6H12O6 (simplify) (solve) (round) (tie it together) CHEM 1701 – Week 8  Mole Math (1 conversion factor calculations) LO 7.3 Perform calculations that convert between mass, moles and particles of a substance PRACTICE (1-step calculation): Use the mole roadmap to perform each conversion. Round all answers to 2 decimal places. Include the chemical formula in your work. MOLECULES → MOLES MOLES → MOLECULES How many moles are in 4.35 × 1023 molecules H2O? How many molecules is equivalent to 0.87 moles H2O? MOLES → MASS MASS → MOLES What is the mass of 2.3 moles H2O? How many moles are in 22.04 g H2O? CHEM 1701 – Week 8 7.3 PRACTICE – Mole Math (1 conversion factor) 1-STEP CALCULATIONS (use 1 conversion factor): Perform each mole math calculation. Round all answers to 2 decimal places. How many atoms are in 5.5 moles of carbon? What is the mass of 4.30 moles of aluminum? How many moles are in 3.71 × 10 23 C 2H 2 molecules? How many moles are in 427 g CuSO4? One of the roles of magnesium in the body is to support a A saline solution is a solution made from water and sodium chloride healthy nervous system. If you have 3.9 × 10 23 magnesium (NaCl). Saline solutions are used as IV solutions to balance electrolytes in atoms, how many moles is this? the body. If you have 127.5 g NaCl, how many moles is this? Sulfur dioxide (SO 2) is a gaseous air pollutant formed when sulfur The word “alcohol” is a broad term that includes many different types containing compounds such as coal, oil and diesel are burned. Sulfur of alcohols. Some alcohols are safe in small amounts, others can be dioxide is an irritant to the skin, eyes, lungs and more. What is the deadly. The form of consumable alcohol found in alcoholic beverages mass of 0.850 moles of sulfur dioxide? is ethanol, C 2H 6O. How many moles are in 32.7 g of ethanol, C 2H6O? CHEM 1701 – Week 8  Mole Math (2 conversion factor calculations) LO 7.3 Perform calculations that convert between mass, moles and particles of a substance Other calculations may require you to use 2 conversion factors from the mole roadmap. Easy breezy. Follow the pattern and use your dimensional analysis skills. PRACTICE 1 (2-step calculation): How many molecules are in 25.0 g H 2O? Round to 2 d.p. ANSWER ANALYSIS/SIDE WORK start: mass (25.0 g H2O) (roadmap) mole 6.02 × 10 23 particles stop: molecules mass × × g 1 mole record Avogadro’s calculate molar mass H2O: record the mass from constant as a fraction in record molar mass as this orientation, include = 2(1.01 g/mole) + 16.00 g/mole the question, include a fraction in this the chemical formula = 18.02 g/mole the chemical formula orientation, include the chemical formula unit remaining (enter data, dimensional analysis) 1 mole H 2 O 6.02 × 10 23 molecules H 2O = 25.0 g H 2O × × 18.02 g H2O 1 mole H2O unit cancels unit cancels (simplify) 25.0 × 1 × 6.02 × 1023 = molecules H2O unit 18.02 × 1 (solve) = 8.35183… × 1023 molecules H2O (round) = 8.35 × 1023 molecules H2O (tie it together) 25 g H 2O is equal to 8.35 × 10 23 molecules H2O. This mass and this number of molecules are the same amount of H2O. PRACTICE 2 (2-step calculation): What is the mass of 2.3 × 10 23 molecules H 2O? Round to 2 d.p. ANSWER ANALYSIS/SIDE WORK start: molecules (2.3 × 10 23 molecules H2O) 1 mole g (roadmap) stop: mass particles × 6.02 × 10 23 particles × mole record molar mass as calculate molar mass H2O: record Avogadro’s a fraction in this record the molecules from orientation, include the = 2(1.01 g/mole) + 16.00 g/mole constant as a fraction in the question, include the this orientation, include chemical formula = 18.02 g/mole chemical formula the chemical formula unit remaining 1 mole H2O 18.02 g H2O (enter data, = 2.3 × 10 23 molecules H 2O × × dimensional analysis) 6.02 × 10 23 molecules H2O 1 mole H2O unit cancels unit cancels (simplify) 2.2 × 10 23 × 18.02 unit = g H2O 6.02 × 10 23 × 1 (solve) = 6.58538… g H2O (round) = 6.59 g H2O (tie it together) 2.3 × 10 23 molecules H 2O is equal to 6.59 g H2O. This number of molecules and this mass are the same amount of H2O. CHEM 1701 – Week 8  Mole Math (2 conversion factor calculations) LO 7.3 Perform calculations that convert between mass, moles and particles of a substance Practice makes perfect! PRACTICE 3 (2-step calculation): What is the mass of 6.75 × 10 24 molecules H 2O? Round to 1 decimal place. ANSWER ANALYSIS/SIDE WORK start: stop: 1 mole g molar mass: (roadmap) particles × × 6.02 × 10 23 particles mole (enter data, dimensional analysis) (simplify) (solve) (round) (tie it together) PRACTICE 4 (2-step calculation): How many molecules are in 150 g H 2O? Round to 2 decimal places. ANSWER ANALYSIS/SIDE WORK start: (roadmap) mole 6.02 × 10 23 particles stop: mass × × g 1 mole molar mass: (enter data, dimensional analysis) (simplify) (solve) (round) (tie it together) CHEM 1701 – Week 8 7.3 PRACTICE – Mole Math (2 conversion factors) 2-STEP CALCULATIONS (use 2 conversion factors): Perform each mole math calculation. Round all answers to 2 decimal places. 1) Calculate the number of atoms in 55.4 g of magnesium. 2) Copper is needed in the body in small amounts to support production of select enzymes. An adult body contains anywhere from 0.0014 g to 0.0021 g of copper per kilogram of body weight. Is 1.5 × 1019 copper atoms within this range? 4) Ethane (C2H6) is an abundant natural gas used in manufacturing of plastics, antifreeze, and detergents. Calculate the mass of 6.7 × 1022 molecules of ethane. CHEM 1701 – Week 8  Credit Laura Labine, PHS Chemistry