Presentation on theme: "How many roses are in 3.5 dozen?"— Presentation transcript:
1 How many roses are in 3.5 dozen? The Mole: Basic ConceptsMeasuring MatterHow many roses are in 3.5 dozen?Eggs and roses are measure in dozensPaper is measured in reamsChemists count atoms in moles!
2 The Mole: Basic Concepts Measuring MatterThe mole (mol), is the SI base unit used to measure the amount of a substance.It is the number of representative particles, carbon atoms, in exactly 12 g of pure carbon-12.x 1023
3 The Mole: Basic Concepts Measuring MatterThe number x 1023 is called Avogadro’s number in honor of the Italian physicist and lawyer Amedeo Avogadro who, in 1811, determined the volume of one mole of a gas.
5 Working at this rate, how many dots could you make The Mole: Basic ConceptsMeasuring MatterHow big is a Mole?When instructed, spend exactly one minute making dots in the box on your paper. Now count the dots.Working at this rate, howmany dots could you makein an hour? In a year?How long would it take you to make a mole of dots?
6 Converting Moles to Particles The Mole: Basic ConceptsConverting Moles to ParticlesSuppose you want to determine how many particles of sucrose are in 3.50 moles of sucrose. You know that one mole contains x 1023 representative particles.
7 Converting Moles to Particles The Mole: Basic ConceptsConverting Moles to Particles
8 Converting Moles to Particles The Mole: Basic ConceptsConverting Moles to ParticlesThere are 2.11 x 1024 molecules of sucrose in moles.
9 Converting Particles to Moles The Mole: Basic ConceptsConverting Particles to MolesNow, suppose you want to find out how many moles are represented by a certain number of representative particles.You can use the inverse of Avogadro’s number as a conversion factor.
10 Converting Particles to Moles The Mole: Basic ConceptsConverting Particles to MolesExample: Zinc is used as a corrosion-resistant coating on iron and steel. It is also an essential trace element in your diet.Calculate the number of moles that contain x 1024 atoms of zinc (Zn).
11 Converting Particles to Moles The Mole: Basic ConceptsConverting Particles to Moles
12 Each atom of carbon-12 has a mass of 12 atomic mass units (amu). The Mole: Basic ConceptsThe Mass of a MoleThe relative scale of atomic masses uses the isotope carbon-12 as the standard.Each atom of carbon-12 has a mass of 12 atomic mass units (amu).The atomic masses of all other elements are established relative to carbon-12.
13 The Mole: Basic Concepts The Mass of a MoleThe mass in grams of one mole of any pure substance is called its molar mass.
14 Converting Mass to Moles The Mole: Basic ConceptsConverting Mass to MolesA roll of copper wire has a mass of 848 g.How many moles of copper are in the roll?
15 Converting Moles to Mass The Mole: Basic ConceptsConverting Moles to MassCalculate the mass of moles of calcium.Use the molar mass of calcium to apply a conversion factor to the number of moles given in the problem.According to the periodic table, the atomic mass of calcium is amu, so the molar mass of calcium is g.
16 Converting Moles to Mass The Mole: Basic ConceptsConverting Moles to Mass
17 Converting Mass to Number of Particles The Mole: Basic ConceptsConverting Mass to Number of ParticlesCalculate the number of atoms in 4.77 g lead.
18 Converting Mass to Number of Particles The Mole: Basic ConceptsConverting Mass to Number of ParticlesNow use a second conversion factor to convert moles to number of particles.
19 Basic Assessment Questions Practice Question 1Calculate the number of molecules in 15.7 mol carbon dioxide, CO2.Answer: x 1024 molecules of CO2
20 Basic Assessment Questions Practice Question 2Calculate the number of moles in 9.22 x 1023 atoms of iron, Fe.Answer: mol Fe
21 Practice Question 3 Calculate the mass of 6.89 mol antimony, Sb. Basic Assessment QuestionsPractice Question 3Calculate the mass of 6.89 mol antimony, Sb.Answer - 839g Sb
22 Basic Assessment Questions Practice Question 4A chemist needs mol selenium, Se, for a reaction. What mass of selenium should the chemist use?Answer: 5.53g Se
23 Basic Assessment Questions Practice Question 5Calculate the number of moles in 17.2 g of benzene (C6H6).Answer: mol C6H6
24 III Empirical and Molecular Formulas A. Percent composition The Mole: Additional ConceptsIII Empirical and Molecular FormulasA. Percent compositionThe percent of an element in a compound can be found in the following way.Click box to view movie clip.
25 A. Calculating Percent Composition The Mole: Additional ConceptsA. Calculating Percent CompositionExample: What is the percent composition of Na2CO3? (assume you have 1 mole if you don’t have a sample size given)2(23.0) Na x total= 43.4% Na12.0 C x= 11.3% C3(16.0) O x= 45.3% O
26 The Mole: Additional Concepts B. Empirical formulasThe empirical formula is the simplest whole- number ratio of atoms of elements in the compound. In many cases, the empirical formula is the actual formula for the compound.
27 B. Empirical Formula from Percent Composition The Mole: Additional ConceptsB. Empirical Formula from Percent CompositionThe percent composition of an unknown compound is found to be 38.43% Mn, % C, and 44.77% O. Determine the compound’s empirical formula.Because percent means “parts per hundred parts,” assume that you have 100 g of the compound.
28 B. Empirical Formula from Percent Composition The Mole: Additional ConceptsB. Empirical Formula from Percent CompositionFollow these rules for Empirical Formulas:Find or start with g of each elementFind moles of each element using the molar mass (P.T.)Divide by smallest moles to get whole #’sMultiply if necessary to get whole #
29 Then calculate the number of moles of each element in the 100 g of compound. The number of moles of manganese may be calculated as follows.=
30 The results show the following relationship mol Mn: mol C: mol O The Mole: Additional ConceptsThe results show the following relationshipmol Mn: mol C: mol O0.6995: :To obtain the simplest whole-number ratio of moles, divide each number of moles by the smallest number of moles.
32 The empirical formula for the compound is MnC2O4
33 Try one on your own!Example: A 9.2 g sample of a compound is 30.4 % N and 69.6 % O. Find its empirical formula.Answer: NO2
34 For many compounds, the empirical formula is not the true formula. The Mole: Additional ConceptsC. Molecular formulasFor many compounds, the empirical formula is not the true formula.Chemists have learned, though, that acetic acid is a molecule with the formula C2H4O2, which is the molecular formula for acetic acid.A molecular formula tells the exact number of atoms of each element in a molecule or formula unit of a compound.
35 Rules for Molecular Formulas The Mole: Additional ConceptsC. Molecular formulasRules for Molecular FormulasKnow molar mass and empirical formula.Compare molar mass of compound with molar mass of empirical formula.Divide molar mass of compound by molar mass of empirical formula - should be a whole #.Then multiply the empirical formula by that #.
36 C. Determining a Molecular Formula The Mole: Additional ConceptsC. Determining a Molecular FormulaMaleic acid is a compound that is widely used in the plastics and textiles industries.The composition of maleic acid is 41.39% carbon, 3.47% hydrogen, and 55.14% oxygen.Its molar mass is g/mol.Calculate the molecular formula for maleic acid.
37 C. Determining a Molecular Formula The Mole: Additional ConceptsC. Determining a Molecular FormulaStart by determining the empirical formula for the compound.
38 You can see by inspection that the smallest whole-number ratio is 1C : 1H : 1O, and the empirical formula is CHO.Next, calculate the molar mass represented by the formula CHO.
39 As stated in the problem, the molar mass of maleic acid is known to be 116.1 g/mol. To determine the molecular formula for maleic acid, calculate the whole number multiple, n, to apply to its empirical formula.Thus, the molecular formula is (CHO)4 = C4H4O4
40 Determining a Molecular Formula The Mole: Additional ConceptsDetermining a Molecular Formula
41 Determining a Molecular Formula The Mole: Additional ConceptsDetermining a Molecular Formula
42 Additional Assessment Questions Calculate the percent composition of aluminum oxide (Al2O3).
43 Additional Assessment Questions Answer52.93% Al; 47.07% O
44 Additional Assessment Questions Determine the percent composition of magnesium nitrate, which has the formula Mg(NO3)2.
45 Additional Assessment Questions Answer16.39% Mg; 18.89% N; 64.72% O
46 Additional Assessment Questions The composition of acetic acid is 40.00% carbon, 6.71% hydrogen, and 53.29% oxygen. Calculate the empirical formula for acetic acid.
48 Additional Assessment Questions Warm-UpThe composition of silver oxalate is 71.02% silver, 7.91% carbon, and 21.07% oxygen. If the molar mass of silver oxalate is g/mol, what is its molecular formula?Answer: Ag2C2O4