Mole / Stoichiometry Calculations www.njctl.org Slide 3 / 157 - PDF document

Slide 1 / 157 New Jersey Center for Teaching and Learning Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Click to go to website: www.njctl.org Slide 2 / 157 Mole / Stoichiometry Calculations www.njctl.org Slide 3 / 157 Table of Contents Click on the topic to go to that section · Avagadro's Number · Molar Mass · Molar Volume · Percent Composition · Emperical Formula

Slide 4 / 157 Avogadro's Number Return to Table of Contents Slide 5 / 157 Moles Recall an atom's atomic mass is equal to the number of protons plus the number of neutrons in the atom. Atomic Number 6 or number of protons (Z) C 12.01 Atomic Mass in amu The unit for atomic mass is amu. Carbon-12 has 6 protons and 6 neutrons. One amu is equal to 1/12 the mass of carbon-12 or approximately the mass of one proton or neutron mass of 1 proton = 1 amu Slide 6 / 157 Moles What if you wanted to measure the mass of one atom in the laboratory? Would it be possible? A single atom has a very small mass. One carbon atom has a mass of about 2.0 x 10 -23 grams .

Slide 7 / 157 The Mole It takes a lot of atoms to give us enough material to directly measure in a lab. Hydrogen has a mass of 1 amu. How many atoms of hydrogen would be needed to make a 1 gram sample of hydrogen? 602,200,000,000,000,000,000,000 The amount 6.02x10 23 is called Avogadro's number or a mole . How big is a mole? Slide 8 / 157 Calculating Avogadro's Number The atomic mass of one carbon atom is 12.01 amu or 2x10 -23 g. How many carbon atoms would it take to get 12.01 grams of carbon? Givens: mass of 1 carbon atom = 2x10 -23 g total mass of carbon atoms = 12.01 g 2x10 -23 g x ? of atoms = 12.01 g 12.01 g ? of atoms = 2x10 -23 g ? of atoms = 6.02 x 10 23 atoms Slide 9 / 157 Holy Mole-y! 1 mole of pennies could One mole of marbles would cover the entire Earth (oceans included) for a be distributed to all the depth of two miles! currently-living people of the world so that they could spend a million dollars per hour every hour (day and night) for the rest of their lives! If you were able to count at the rate of 1 million numbers a second, it would take about 20 billion years to count out one mole!

Slide 10 / 157 The Mole A mole is just a grouping of numbers...like dozen, ream, etc. A dozen means 12 of something. A mole means 6.02 x 10 23 of something. Common Grouping Quantities 1 dozen = 12 1 gross =144 1 ream = 500 1 mole = 6.02 x 10 23 Slide 11 / 157 1 How many eggs are in two dozen eggs? A 12 B 24 C 0.0833 D 2 E 6.02 x 10 23 Slide 12 / 157 2 How many eggs are in half a dozen eggs? A 12 B 24 C 6 D 0.5 6.02 x 10 23 E

Slide 13 / 157 3 How many particles of sand are in 0.5 moles of sand? 1.5 x 10 23 A B 3.01 x 10 23 C 6.02 x 10 23 D 1.2 x 10 24 E 6.02 x 10 24 1 mole = 6.02 x 10 23 Slide 14 / 157 4 How many pieces of gold dust are in 2 moles of gold dust? A 1.5 x 10 23 B 3.01 x 10 23 C 6.02 x 10 23 D 1.2 x 10 24 E 6.02 x 10 24 1 mole = 6.02 x 10 23 Slide 15 / 157 5 How many dozen eggs are in a container of 6 eggs? A 4 B 0.5 C 1 D 2 6.02 x 10 23 E

Slide 16 / 157 6 How many dozen eggs are in a container of 18 eggs? 1.5 A B 3 C 0.67 D 2 6.02 x 10 23 E Slide 17 / 157 7 The Milky Way Galaxy may have up to 400 billion (4 x 10 14 stars). How many moles of stars does it have? A 1.5 x 10 9 B 6.7 x 10 -10 C 10 D 0.5 6.02 x 10 23 E 1 mole = 6.02 x 10 23 Slide 18 / 157 8 Mathematicians estimate Earth's beaches contain nearly 5.6 x 10 21 grains of sand. How many moles of sand are on Earth's beaches? A 1.5 B 9.3 x 10 -3 C 10 D 107.5 6.02 x 10 23 E 1 mole = 6.02 x 10 23

Slide 19 / 157 Measuring Matter with Moles The mole is the SI unit for measuring the amount of particles in a chemical substance. 1 mole of Carbon Slide 20 / 157 Measuring Matter with Moles One mole (mol) of a substance is 6.02 x 10 23 representative particles of that substance. N Where: n = N A n is the number of moles N is the total number of particles N A is Avogadro's Number 6.02 x 10 23 Slide 21 / 157 Measuring Matter with Moles N A = 6.02 x10 23 atoms How many moles of Gold are there in a sample containing 3.01 x 10 23 atoms of Gold?

Slide 22 / 157 9 How many atoms of titanium are in a sample containing 0.5 mole of titanium? A 1.5 x 10 23 N n = B 3.01 x 10 23 N A N A = 6.02 x 10 23 C 6.02 x 10 23 D 1.2 x 10 24 E 6.02 x 10 24 Slide 23 / 157 10 How many atoms of sodium are in a sample containing 2.0 moles of sodium? A 1.5 x 10 23 N n = B 3.01 x 10 23 N A N A = 6.02 x 10 23 C 6.02 x 10 23 D 1.2 x 10 24 6.02 x 10 22 E Slide 24 / 157 11 How many moles of potassium are in a sample containing 3.01 x 10 23 atoms of potassium? 1.0 A N n = N A 2.0 B N A = 6.02 x 10 23 C 0.5 D 0.75 6.02 x 10 24 E

Slide 25 / 157 12 How many moles of potassium are in a sample containing 1.2 x 10 24 atoms of potassium? A 0.25 mol N B 0.50 mol n = N A C 1.0 mol N A = 6.02 x 10 23 D 2.0 mol 3.0 mol E Slide 26 / 157 13 How many moles of tungsten atoms are there in a sample containing 1.8 x 10 24 atoms of tungsten? A 0.33 mol N n = 0.50 mol B N A C 1.0 mol N A = 6.02 x 10 23 1.5 mol D E 3.0 mol Slide 27 / 157 14 How many moles of silver are there in a pure sample containing 1.5 x 10 23 atoms of silver? A 0.10 mol N n = B 0.25 mol N A C 0.50 mol N A = 6.02 x 10 23 D 1.0 mol E 1.5 mol

Slide 28 / 157 15 How many atoms are there in 5.00 mol of hafnium? A 6.02 x10 23 atoms N B 1.20 x 10 23 atoms n = N A C 1.20 x 10 22 atoms N A = 6.02 x 10 23 D 3.43 x 10 23 atoms E 3.01 x 10 24 atoms Slide 29 / 157 Measuring Matter with Moles A mole of ANY substance contains Avogadro’s number of representative particles, or 6.02 x 10 23 representative particles. 1 mole of C atoms = 6.02 X 10 23 atoms of C 1 mole of pick-up trucks = 6.02 x 10 23 pick-up trucks The term representative particle refers to the species or types of particles in the substance For Example: atoms, molecules, formula units, ions Slide 30 / 157 Measuring Matter with Moles laboratory sample size molecule of H 2 O H Avagadro's O number of H molecules 18.0 amu (6.02 x10 23 ) 1 mol H 2 O (18.0 g) In 1 mole of carbon there are 6.02 x 10 23 carbon atoms. In 1 mole of water there are 6.02 x 10 23 water molecules. In 1 mole of NaCl there are 6.02 x 10 23 formula units.

Slide 31 / 157 16 Formula units refer to particles of __________ compounds and molecules refer to particles of __________ compounds. A molecular/covalent, ionic B ionic, molecular/covalent C atoms, molecular D atoms, ionic E ionic, atomic Slide 32 / 157 17 How many molecules are there in 2.10 mol CO 2 ? A 3.79 x 10 24 N n = B 3.49 x 10 -24 N A C 1.05 x 10 -23 N A = 6.02 x 10 23 D 2.53 x 10 24 E 1.26 x 10 24 Slide 33 / 157 18 How many moles of helium atoms are there in a pure sample containing 6.02 x 10 24 atoms of helium? A 2.0 mol N n = N A B 4.0 mol N A = 6.02 x 10 23 C 6.0 mol D 10.0 mol E 2.4 x 10 24 mol

Slide 34 / 157 19 How many moles of NaCl are there in a pure sample containing 6.02 x 10 23 formula units of sodium chloride, NaCl? A N 1.0 mol n = N A B 2.0 mol N A = 6.02 x 10 23 C 4.0 mol D 6.0 mol E 6.02 x 10 23 mol Slide 35 / 157 20 How many formula units of Pb(NO 3 ) 2 are there in 0.5 mole of Pb(NO 3 ) 2 ? N n = N A A 0.5 formula units N A = 6.02 x 10 23 B 2.0 formula units C 3.01 x 10 23 formula units D 1.2 x 10 24 formula units E 6.02 x 10 23 formula units Slide 36 / 157 Real World Application Calcium deficiency can cause osteoporosis (weakening of the bones). The minimum amount of calcium in 1 mL of blood should be around 1.3 x 10 18 atoms. A patient has her blood tested and the lab finds there are 3 x 10 -5 moles of calcium in the blood. Is this patient at risk for osteoporosis? (6.02 x 10 23 atoms/mole) x (3 x 10 -5 moles) = 1.8 x 10 23 atoms Ca slide for answer This exceeds the normal range so they are OK!

Slide 37 / 157 Review: Ionic and Molecular Compounds The total number of atoms or ions in a compound depends on electronegativity and bonding. Ionic Compounds Molecular Compounds NaCl H 2 O 1 Na + ion 1 Cl - ion 2 hydrogen 1 oxygen atoms atom K 2 CrO 4 2 K + ions 1 CrO 42- ion C 6 H 6 6 hydrogen 6 carbon Sn(OH) 2 atoms atoms 1 Sn 2 + ion 2 OH - ions Slide 38 / 157 Review: Ionic and Molecular Compounds Chemicals are composed of more than one molecule or formula unit. To indicate more than one molecule or formulat unit, add a coefficient in front of the compound. Example: six molecules of carbon dioxide = 6CO 2 . How many atoms of carbon and oxygen are in 6CO 2 ? 6 atoms of carbon and 12 atoms of oxygen Move to reveal answer Slide 39 / 157 Review: Ionic and Molecular Compounds Molecular Compounds - Fill in Ionic Compounds - Fill in 3 NaCl 6 H 2 O 3 __ Na + ions __ Cl - ions 3 __hydrogen __oxygen 2 K 2 CrO 4 atoms atom __K + ions __CrO 42- ions C 6 H 6 Sn(OH) 2 4 __carbon __hydrogen atoms atoms __Sn 2 + ions __OH - ions