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 Ionic Compounds - Fill in Molecular Compounds - Fill in 3 NaCl H 2 O 6 3 __ Cl - ions 3 __ Na + ions __hydrogen __oxygen K 2 CrO 4 atoms atom 2 __K + ions __CrO 42- ions C 6 H 6 Sn(OH) 2 4 __carbon __hydrogen atoms atoms __OH - ions __Sn 2 + ions
Slide 40 / 157 Converting Moles to Number of Particles molecule of H 2 O laboratory sample size H O H Avagadro's number of 18.0 amu molecules 23 ) (6.02 x10 1 mol H 2 O (18.0 g) In one mole of water molecules there are: H 2 O 2 moles of 1 mole of hydrogen atoms oxygen atoms 1 x 6.02x10 23 atoms 2 x 6.02x10 23 atoms of oxygen of hydrogen
Slide 41 / 157 Converting Moles to Number of Particles In 3 moles of sodium chloride formula units there are: 3NaCl 3 moles of 3 moles of Cl - ions Na + ions
Slide 42 / 157 21 How many hydrogen atoms are in six molecules of ethylene glycol, the major component in antifreeze? The formula for ethylene glycol is: HOCH 2 CH 2 OH. A 6 atoms of H N n = N A B 36 atoms of H C 6 x 6.02 x 10 23 atoms of H Answer N A = 6.02 x 10 23 D 36 x 6.02 x 10 23 atoms of H E 6.02 x 10 23 atoms of H
Slide 43 / 157 22 How many CO 32- ions are in one formula unit of CaCO 3 ? N n = A 1 ion N A B 3 ions N A = 6.02 x 10 23 C 6 x 6.02 x 10 23 ions Answer D 36 x 6.02 x 10 23 ions E 6.02 x 10 23 ions
Slide 44 / 157 23 How many K + ions are there in two formula units of potassium hydroxide, 2KOH? N n = A 1 K + ion N A B 2 K + ions N A = 6.02 x 10 23 C 1 x 6.02 x10 23 ions of K + D 2 x 6.02 x 10 23 ions of K + Answer E 3.12 x 10 23 ions of K +
Slide 45 / 157 24 How many sulfide ions (S 2- ) are there in 2.0 moles of ammonium sulfide,(NH 4 ) 2 S? A 2.0 ions N n = N A = 6.02 x 10 23 B 1.2 x 10 24 ions N A C 2.4 x 10 24 ions Answer 6.02 x 10 23 ions D E none
Slide 46 / 157 25 How many ammonium ions (NH 4 + ) are there in 2.0 moles of ammonium sulfide, (NH 4 ) 2 S? A 2.0 ions N 1.2 x 10 24 ions B n = N A C 2.4 x 10 24 ions N A = 6.02 x 10 23 D 6.02 x 10 23 ions Answer E 8.0 ions
Slide 47 / 157 Real World Application Hemoglobin is a protein that carries O 2 around your body. The formula for it is approximately C 2800 H 4800 N 3200 O 800 S 8 Fe 4 . If a patient has 2 x 10 16 atoms of Fe, how many moles of Hb would be present? moles of Fe: n = N/Na --> (2 x 10 16 atoms)/(6.02 x 10 23 atoms/n)= 3.3 x 10 -7 moles Fe moles of Hb: There are 1 Hb/4 Fe --> (3.3 x 10 -7 moles Fe)/(4 moles of Fe/Hb) slide for answer = 8.2 x 10 -8 moles Hb
Slide 48 / 157 Molar Mass Return to Table of Contents
Slide 49 / 157 Mass of Compounds The total mass of a chemical compound can be calculated by using the masses on the Periodic Table. Example: Calculate the mass of the compound Magnesium Chloride (MgCl 2 ) Mg = 24.305 amu 2Cl = (2)35.453 amu + Mass of MgCl 2 95.211 amu
Slide 50 / 157 Masses of Elements/Compounds Units used for elements Atomic mass amu (like F, V, etc..) only used for ionic Formula mass or compounds (like amu Formula weight (FW) NaCl, MgO, etc..) only used for molecular Molecular mass or amu compounds (like Molecular weight CO 2 , H 2 O, etc..) only
Slide 51 / 157 26 What is the formula weight of sodium bromide? A 79.904 amu 102.894 amu B C 205.780 amu Answer D 300.120 amu E 605.102 amu
Slide 52 / 157 27 What is the formula weight of Pb(NO 3 ) 2 ? A 79.90 amu 102.89 amu B C 205.78 amu Answer D 331.34 amu E 605.10 amu
Slide 53 / 157 28 What is the molecular mass of 3H 2 O 2 ? A 17 amu 34 amu B C 68 amu Answer D 102 amu E 204 amu
Slide 54 / 157 Molar Mass (M) A mole represents the number of atoms it takes to convert from a single atomic mass in amu to the same mass in grams. The mass in grams of one mole of any substance is its molar mass (M) . Each of the bars shown below equals one mole of a pure element. 1 mole of Copper = 63.546 g 1 mole of Aluminum = 26.982 g
Slide 55 / 157 Molar Mass (M) One mole of carbon, sulfur and silver are shown . 1 mol of sulfur 1 mol of Carbon atoms 32.0 g of S atoms = 12.0 g 1 mol of silver = 107.9 g of Ag
Slide 56 / 157 How is the atomic mass of an element related to the molar mass? Average atomic mass of 1 atom of Kr = 83.8 amu. 1 mole (6.02 x 10 23 atoms) of Kr = 83.8 grams. The atomic mass of an element expressed in grams is the mass of one mole or molar mass (M) of the element. 1 mole of Kr = 83.8 grams Molar mass of Kr = 83.8 grams or 83.8 g/mol 1 mol
Slide 57 / 157 Molar Mass The molar mass of an element or compound can be used to convert directly from masses in amu to masses in grams. Units used for elements Gram atomic mass grams (like F, V, etc..) only used for ionic Gram formula mass or compounds (like grams Formula weight (FW) NaCl, MgO, etc..) only used for molecular Gram molecular mass or grams compounds (like Molecular weight CO 2 , H 2 O, etc..) only
Slide 58 / 157 Molar Mass To convert from moles to mass, or vice versa, use the following formula. m Where: n = M n is the number of moles m is the mass of the sample M is the molar mass of the substance.
Slide 59 / 157 29 How many moles are in a 64-gram sample of pure sulfur? Answer m n = M
Slide 60 / 157 30 How many moles are in a 72-gram sample of pure magnesium? Answer m n = M
Slide 61 / 157 31 What is the mass, in grams, of 2 moles of carbon? Answer m n = M
Slide 62 / 157 32 What is the mass, in grams, of 5 moles of iron? Answer m n = M
Slide 63 / 157 33 How many grams is 2.0 mol neon atoms? Answer m n = M
Slide 64 / 157 Diatomic Molecules (Recall the seven diatomic molecules: HONClBrIF) The molar mass of these molecules will be twice their atomic mass. Examples: M of hydrogen gas: H 2 = (2 x 1) = 2 g/mol M of bromine liquid: Br 2 = (2 x 79.9) = 159.8 g/mol M of fluorine molecules: F 2 = (2 x 19) = 38 g/mol
Slide 65 / 157 34 How many grams is 1.0 mole of hydrogen molecules? Answer m n = M
Slide 66 / 157 35 How many grams is 0.50 mol of oxygen molecules? Answer m n = M
Slide 67 / 157 Molar Mass of a Compound The molar mass of a compound is the sum of the molar masses of all the elements in the compound. To calculate the molar mass of a compound, find the number of grams of each element in one mole of the compound. Then add the masses of the elements in the compound. 3(16.000) g/mol = 80.650 g/mol 32.065 g/mol + Molar mass of SO 3 = 80.650 g/mol
Slide 68 / 157 Molar Mass of a Compound Note the different molar masses of these two compounds. 18 g of H 2 O = 180 g of glucose (C 6 H 12 O 6 ) 1 mole H 2 O = 1 mole glucose
Slide 69 / 157 [*] 36 What is the molar mass of K 2 O, potassium oxide? Answer
Slide 70 / 157 37 What is the molar mass of CaCO 3 , calcium carbonate found in eggshells? A 50 amu B 50 grams/mol C 100 amu D 100 grams/mol Answer
Slide 71 / 157 38 What is the molar mass of carbon dioxide? A 28 amu B 28 grams/mol C 44 amu D Answer 44 grams/mol
Slide 72 / 157 39 What is the molar mass of ammonia, NH 3 ? A 17 amu B 17 grams/mol C 45 amu D 45 grams/mol Answer
Slide 73 / 157 Summary of Molar Mass Molar mass is the mass of 1 mole of a substance (measured in g/mol). The atomic mass will be the same number as the molar mass (measured in amu). The difference is that the atomic mass refers to only one representative particle and molar mass refers to one mole (6.02 x 10 23 ) of representative particles.
Slide 74 / 157 40 What is the mass of one formula unit of NaCl? A 17 amu B 17 grams/mol C 58.5 amu Answer D 58.5 grams/mol
Slide 75 / 157 41 What is the mass of one molecule of water? A 18 amu B 18 grams/mol C 8 amu Answer D 8 grams/mol
Slide 76 / 157 42 The chemical formula of aspirin is C 9 H 8 O 4 . What is the mass of 0.200 moles of aspirin? Answer m n = M
Slide 77 / 157 43 How many moles of O are in 2.4 X 10 24 molecules of SO 3 ? Answer
Slide 78 / 157 How many grams of iron are in a 68 gram sample of Fe 2 O 3 ? n = m/M 68 g Fe 2 O 3 = 0.43 mol Fe 2 O 3 x (2 mol of Fe) = 0.86 mol Fe 160 g Fe 2 O 3 then... n = m/M --> m = n*M = (0.86 n Fe)(56 g/n) = 48 grams Fe Move to see answer OR use dimensional analysis M of Fe2O3 = 160 g/mol M of Fe = 56g/mol 69 g Fe 2 O 3 x 1 mol Fe 2 O 3 x 2 mol Fe x 56g Fe = 48 g Fe 160g Fe 2 O 3 1 mol Fe 2 O 3 1 mol Fe
Slide 79 / 157 44 The molar mass of oxygen (O 2 ) is: equal to the mass of one mole of oxygen atoms. A B 16.0 g/ mol C Answer 32.0 g/ mol none of the above D equal to the mass of one oxygen atom. E m n = M
Slide 80 / 157 45 There are more moles of CO 2 in a 44 g sample of carbon dioxide gas than there are moles of helium atoms in a box containing 2 x 10 23 atoms of He. True False Answer
Slide 81 / 157 Molar Volume Return to Table of Contents
Slide 82 / 157 The Mole and the Volume of a Gas The volume of a gas varies with temperature and pressure. But comparisons between gases can be made by designating a standard temperature and pressure (STP).
Slide 83 / 157 STP (Standard Temperature and Pressure) Standard Temperature (T) is considered 0°C (273 K), the temperature at which water freezes. Standard Pressure (P) is considered 1 atmosphere (101.3 kPa), or the pressure of the atmosphere at sea level. At STP, 1 mole of gas occupies a volume of 22.4 liters (L) V m = 22.4 L For the time being, we will treat all gases as if they are at STP.
Slide 84 / 157 The Mole and the Volume of a Gas The volume occupied by one mole of gas is called the molar volume and has the symbol, V m . It is the same for all gases. At STP; V m = 22.4 liters (L). 1 mole of gas = 6.02 x 10 23 particles = 22.4 L Notice that this statement does not depend on the type of gas. It's true of all gases.
Slide 85 / 157 The Mole and the Volume of a Gas At STP; V m = 22.4 liters (L). This is true because in a gas the molecules are so far apart that they take up almost no space...the volume of a gas is mostly empty space, regardless of the type of gas. So when it comes to volume (at STP) all gases are created equal. 1 mole of He gas occupies 22.4 L @STP 1 mole of HCl gas occupies 22.4 L @STP
Slide 86 / 157 46 Which of the following must be true about 2 moles of H 2 gas vs. 2 moles of CO 2 gas at the same temperature and pressure? A Each sample will have the same density B The same # of atoms will be present in each sample C Each sample will have the same mass Answer D Each sample will occupy the same volume E None of these are true
Slide 87 / 157 The Mole and the Volume of a Gas x 10 23 representative particles, of any At STP, 1 mole or, 6.02 gas occupies a volume of 22.4 L. The quantity 22.4 L is called the molar volume of a gas. V n = V m Where: n is the number of moles of gas V is the volume of the gas V m is 22.4 L, at STP
Slide 88 / 157 47 How many moles are there in 44.8 liters (at STP) of fluorine gas? Answer V n = V m V m = 22.4 L
Slide 89 / 157 48 How many moles of atoms are there in 22.4 liters (at STP) of Xenon? Answer V n = V m V m = 22.4 L
Slide 90 / 157 49 What is the volume (in liters at STP) of 1.00 mole of sulfur dioxide? Answer V n = V m V m = 22.4 L
Slide 91 / 157 50 What is the volume (in liters at STP) of 2.50 moles of carbon monoxide? Answer V n = V m V m = 22.4 L
Slide 92 / 157 51 What is the volume (in liters at STP) of 4.00 moles of Nitrogen? Answer V n = V m V m = 22.4 L
Slide 93 / 157 Real World Application An inflated airbag requires 60 L of nitrogen gas (N 2 ) at STP in order to protect the occupant of the vehicle. How many moles of nitrogen gas would need to be created in 40 milliseconds to inflate the airbag?
Slide 94 / 157 Combining the three mole formulas We now have three formulas for finding the number of moles of a substance. Which one should be used depends on whether you are given (or trying to find): N the number of particles n = N A = 6.02 x 10 23 N A m the mass of a substance n = M V the volume of a gas n = V m V m = 22.4 L at STP
Slide 95 / 157 Combining the three mole formulas Sometimes two of these formulas must be used together to solve a problem. Here's an example: How many atoms of carbon are present in a 24 g sample of pure carbon? N n = N A = 6.02 x 10 23 N A m n = M V n = V m V m = 22.4 L at STP
Slide 96 / 157 Combining the three mole formulas How many atoms of carbon are present in a 24 g sample? Step 1: find the number of moles of C present: n = m = 24g = 2.0 mol 12g/mol M Step 2: find the number of atoms in 2.0 moles. n = N N = n(N A ) rearrange substitute: N A 2.0mol x 6.02x10 23 atoms/mol = 1.2x10 24 atoms
Slide 97 / 157 Mole Road Map N (Particles: atoms, ions, molecules, etc.) N N A =6.03*10 23 particles/mole n= M: molar mass N A found using the n periodic table n= V n= m V m =22.4 Liters/mole V m M V m (Volume) (mass)
Slide 98 / 157 52 How many molecules are there in 44.8 liters (at STP) of oxygen gas? Answer V n = V m V m = 22.4 L
Slide 99 / 157 53 How many atoms are there in 11.2 liters (at STP) of molecular oxygen ( oxygen gas)? Answer N n = N A = 6.02 x 10 23 N A m n = M V n = V m V m = 22.4 L at STP
Slide 100 / 157 54 What is the mass of 44.8 liters (at STP) of molecular oxygen? Answer N n = N A = 6.02 x 10 23 N A m n = M V n = V m V m = 22.4 L at STP
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