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## Chapter 10

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**Chapter 10**Chemical Quantities**Measuring Matter**• Matter can be measured by 3 methods • By count • the number of CDs you have • The number of atoms or molecules you have • By mass or weight • You buy vegetables by the pound • The mass(g) of a compound or element you have • By volume • You buy soda in two liter bottles • The number of milliliters of a substance you have**Measuring Matter**• Every measurement has a MAGNITUDE and DIMENSION • Magnitude is the numerical value • Dimension is the unit of measurement (gram, pound, etc)**Conversion factors**• Relationships between two numbers • 1 Dozen = 12 things • 1 Pair = 2 things • 1 Minute = 60 seconds • 1000 Meter= 1 kilometer**Conversion Factors continued**• Can also be written as fractions… • 1 dozen 12 things**Dimensional Analysis**• Using conversion factors (T boxes ) to solve problems is called dimensional analysis**Finding Mass from a Count**• What is the mass of 90 average-sized apples if a dozen apples has a mass of 2.0kg? Hint: use “T” box 1 dozen 2.0kg 90 apples 12 apples 1 dozen apples = 15 kg or 15,000g**Practice Problems**• If 0.20 bushel is 1 dozen apples and a dozen apples has a mass of 3.0 kg, what is the mass of 0.50 bushel of apples? 7.5 kg or 7500g**Assume 3.0 kg of apples is 1 dozen and that each apple has 8**seeds. How many apple seeds are in 14kg of apples? 448 seeds**When determining quantities in chemistry the method is the**same….. You just use different units !!!!!!!!**Comparing mass of molecules**-mass is measured in a.m.u. (atomic mass units) -Formula mass: the mass of the atoms in the compound in amu - round to the nearest hundredth. Formula Mass= H H Ex. Water 1.01 1.01 1.01 O 1.01 +16.00 16.00 18.02 a.m.u.**Finding formula mass:**1. Multiply # of atoms of each element by its mass (amu) 2. Add them together Ex. Fe2O3 Fe = 55.85 x 2 = 111.70 O = 16.00 x 3 = +48.00 = 159.70 amu**Calculate the formula mass for each of the following:**AgNO3 = KC2H3O2 =**Formula Mass of Hydrates*** Remember f.m. of hydrate includes the mass of the water • Calculate the f.m. of compound 2. Calculate the f.m. of H2O x # of molecules 3. Add together**Ex. BaCl2 2H2O**Step 1: Ba= 1 x 137.33 = 137.33 Cl = 2 x 35.45 = + 70.90 208.23 Step 2: H= 2 x 1.01 = 2.02 O= 1 x 16.00 = +16.00 18.02 x 2 =36.04 Step 3: 208.23 + 36.04 = 244.27a.m.u.**But we have a problem…..**We can’t measure amu’s in lab so scientists had to come up with a measurement we could use.**The Mole**• Mole = 6.02 x 1023 particles of a substance –could be atoms, molecules, or formula units • Ex: A mole of hydrogen atoms is 6.02 x 1023 hydrogen atoms, a mole of paper is 6.02 x 1023 piece of paper • 6.02 x 1023 is known as Avogadro’s number-Avogadro was an Italian scientist in the 1800’s helped clarify the difference between atoms and molecules**A mole of any substance contains 6.02 x 1023**representative particles**How many molecules of water would there be in a mole of**water?**mole is a unit**• TedEd**The Mass of a Mole (MOM) of a substance = formula mass in**grams**Mass of a Mole**• The atomic mass of an element expressed in grams is the mass of one mole of that element. • Example- 1 mole of carbon is 12.0 grams. • The molar mass of any two elements contain the same number of atoms • Ex: a dozen apples – 12 apples • a dozen oranges – 12 oranges**Molar mass (MOM)**1 mole of carbon atoms (6.02 x 1023atoms) Formula Mass 1 atom carbon 12.01 amu 12.01 grams**Would a mole of ping pong balls have the same mass as a mole**of bowling balls?**Would a mole of carbon atoms have the same mass as a mole of**sodium atoms? What would a mole of carbon atoms weigh in grams? What about a mole of sodium atoms?**Mass of a Mole of a Compound**• Find the number of grams of each element in the compound, then add the masses together. • Ex: Find the molar mass of water. • Step 1- write down the formula H2O • Step 2- determine masses of each element 2 H atoms x 1.0 g = 2.0 g H 1 O atom x 16.0 g = 16.0 g O Step 3- add masses together 16.0 g O + 2.0 g H = 18.0 g H2O The molar mass of water is 18.0 g/mol**Cl**Cl H H O C Cl Cl Which would have a higher mass…. a mole of water or a mole of carbon tetrachloride?**We can use the molar mass of a compound to convert between**moles and masses of compounds**Avogadro’s Number (6.02 x 1023)**-is the # of atoms in the molar mass of an element. 12.01g Carbon = 6.02 x 1023 atoms**OR**- is the # of molecules in the molar mass of a compound. 18.02g H2O = 6.02 x 1023 molecules**Finding the Mass of a Mole of a compound**• The decomposition of hydrogen peroxide (H2O2) provides sufficient energy to launch a rocket. What is the molar mass of hydrogen peroxide? 34.02g**Practice problems**• Find the molar mass (MOM) of PCl3. 137.32g/mol • What is the molar mass(MOM) of 1.00 mol sodium hydrogen carbonate? (NaHCO3) 84.01g**Mole to Mass Conversion**• Use the molar mass of an element or compound to convert between the mass of a substance and the moles of a substance • Conversion factor 12 inches = 1 foot 3 feet = 1 yard molar mass = 1 mole ex: 18.0 g H2O = 1 mol H2O**Mole – Mass Relationship**• Use the molar mass of an element or compound to convert between the mass and moles of a substance. • ****Remember: molar mass = 1mol**Let’s try them with “T” boxes/conversion factors…**• What is the mass of 3.4 moles of Mg? • What is the mass of 23.9 moles of Sn? • How many grams are in 18.1 moles of F? • How many grams are in 98.5 moles of Zn? • How many grams are in 2.7 x102mol Pb?**Find the mass in grams of 4.52x10-3mol of C20H42.**1.27g C20H42 • Calculate the mass in grams of 2.50 mol of Iron(II)hydroxide. 225g Fe(OH)2**What is the mass of 3.0 mol of NaCl?**176g • Whatis the mass of 9.45 mol of Aluminum oxide? 964g Al2O3**Find the number of moles in 3.70 x10-1g of boron.**3.43 x 10-2 mol B Calculate the number of moles in 75.0 g dinitrogen trioxide. 0.987 mol N2O3**Which would have more atoms a mole of carbon or a mole of**sulfur? … both would have 6.02 x 1023 atoms**Converting # of atoms to Moles**How many moles of magnesium is 1.25 x 10 23 atoms of magnesium? (hint: use “T” box) 2.08 x 10-1mol Mg or 0.208 mol Mg**Practice Problems**How many moles is 2.80 x 1024 atoms of silicon? 4.65mol Si How many moles is 2.17 x 1023 representative particles of bromine? 0.360 mol Br2**Use “T” Boxes to calculate these…..**• How many moles is 15.38 x 1023 atoms of Ni? • How many moles is 2 x 1032 atoms of Ti? • How many moles is 17.93 x 1018 atoms of Be? • How many moles is 8.7 x 10 23 atoms of Ag?**Cl**Cl H H O C Cl Cl Which would have more atoms…. a mole of water or a mole of carbon tetrachloride? …so a mole of different compounds can have different numbers of atoms**Converting Moles of Compound to Number Of Atoms**• Is C an element or compound? • Element- 1 mole is 6.02 x 1023 atoms • Is CO2 an element or compound? • Compound – 1 mole is 6.02 x 1023 molecules (or formula units) • Remember a mole is 6.02 x 1023 things !!!