Unit 2 Intro to Quantitative Chemistry CDO CP CHemistryTrimble

PERIODIC TABLE CDO IB Chemistry SL2

ELEMENTS ON THE PERIODIC TABLE The elements on the periodic table are classified into one of three categories: METALS NONMETALS METALOIDS CDO IB Chemistry SL3

A. Metallic Character Metals Nonmetals Metalloids B Si Ge As Sb Te Po At

Amounts of a Substance CP Chemistry5

What is a mole? An amount of substance that contains the same number of particles as 12 g of C-12 Analogy A dozen is 12 A ream is 500 A mole is 6.02 x 10 23

Avogadro’s Number 6.02 x (L) Example: Determine the number of atoms in 12 g of C-12 if the mass of 1 atom of C -12 is x g. 7CDO IB Chemistry SL

Molar Mass (M r ) By definition, M r is the mass of 1 mol of a substance (i.e., g/mol). The molar mass of an element is the average mass for the element that we find on the periodic table. The M r of a compound is the sum of each of the relative molecular mass of each element multiplied by the number of the atoms in the formula CDO IB Chemistry SL8

Example: Calculating Molar Mass Calculate the molar mass for each of the following elements/compound: 1.CO 2 2.H 2 SO 4 3.S 4.Ca(C 2 H 3 O 2 ) 2 CDO IB Chemistry SL9

White Board Practice Find the M r for each of the following compounds or atoms: HNO 3 H 2 O O 2 Mg CDO IB Chemistry SL10

Using Moles Moles provide a bridge from the molecular scale to the real-world scale. If the substance is an element we will count atoms using Avogadro's number if the substance is a compound we will count molecules, formula units or ions 11CDO IB Chemistry SL

Converting to Determine number of Particles Equation: n = N N A Where n = moles N = # of particls N A = Avogadros # CDO IB Chemistry SL12 N nNANA

Examples: Using Avogadro’s Number How many atoms of Au are there in 0.36 moles of Au? How many moles are there in 3.46 x molecules of water? CDO IB Chemistry SL13

Converting Between Mass and Moles Equation: n = m M r Where n = moles m = grams Mr = molar mass CDO IB Chemistry SL14 m n MrMr

Example: Using Moles in Calculations – Molar Mass How many moles of tin are there in 250 grams of tin? How many moles of SO 2 is present in 0.45 grams of sulfur dioxide? CDO IB Chemistry SL15

White Board Practice How many moles are there in 36 g of Sulfur? How many grams are there in 3.2 moles of CO 2 ? How many atoms are there in 1.62 moles of Calcium? How many moles is 3.61 x molecules of sulfuric acid? CDO IB Chemistry SL16

Mole Relationships One mole of atoms, ions, or molecules contains Avogadro’s number of those particles. One mole of molecules or formula units contains Avogadro’s number times the number of atoms or ions of each element in the compound. 17CDO IB Chemistry SL

Molecules and Chemical Formulas 18

Molecules Molecules are groups of atoms chemically bonded together. Molecules may be elements or compounds. CDO IB Chemistry SL19

Molecular Elements and Allotropes Some Elements exist as molecules Diatomic elements (molecules) Phosphorus exists as a tetratomic molecule Some elements exist in a variety of forms (Allotropes) Carbon: graphite; diamond; buckminsterfullerine Phosphorus - red and white Sulfur - S 6 and S 4 CDO IB Chemistry SL20

Diatomic Molecules These seven elements occur naturally as molecules containing two atoms. 21CDO IB Chemistry SL

Molecules and Molecular Compounds Molecular compounds - molecules containing atoms from two or more different elements Covalent bonds - the force holding the atoms together in a molecular compound by the sharing of electrons CDO IB Chemistry SL22

Formulas A compound is represented by using the symbols for the elements of which it is composed Subscripts are used to indicate how many atoms of a particular element exist in the compound If there is only one atom of a particular element, the one is assumed CDO IB Chemistry SL23

Formulas, con’t Changing the subscripts changes the compound consider H 2 O and H 2 O 2 Two different compounds can, however, share the same chemical formula dimethyl ether and ethyl alcohol both have the formula C 2 H 6 O CDO IB Chemistry SL24

Ions When atoms lose or gain electrons, they become ions. Cations are positive and are formed by elements on the left side of the periodic table Anions are negative and are formed by elements on the right side of the periodic table 25CDO IB Chemistry SL

How charged species arise Neutral atoms and molecules have the same number of protons and electrons Cations have more protons than electrons resulting from the loss of an electron Anions have more electrons than protons resulting from the gain of an electron CDO IB Chemistry SL26

Common Monatomic Ions CDO IB Chemistry SL27 Main Group Elements Group 1, 2 – All Metals – Group # = Charge of the Cation Group 3 – Metals (doesn’t include B) – Group # = Charge of Cation Group 5 – Non Metals – Group # - 8 = Charge of Anion Metal – Bi – Group # = Charge Group 6, 7 – Non Metals Group # - 8 = Charge of Anion Group 0 – Doesn’t Form Ions!!

Common Variable Charge Cations CDO IB Chemistry SL28 Copper – Cu 1+ and Cu 2+ Iron – Fe 2+ and Fe 3+ Lead – Pb 2+ and Pb 4+ Gold – Au 1+ and Au 3+ Tin – Sn 2+ and Sn 4+

Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals. (Cation and Anions) due to electrostatic attraction 29CDO IB Chemistry SL

Writing Formulas Because compounds are electrically neutral, one can determine the formula of a compound this way: The charge on the cation becomes the subscript on the anion. The charge on the anion becomes the subscript on the cation. If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor. 30CDO IB Chemistry SL

Examples: Writing the Formula for Ionic Compounds Ca and Cl Ba and F Na and S CDO IB Chemistry SL31

Polyatomic ions Cations or anions consisting of groups of atoms that are covalently bonded to each other When more than one appears in a formula unit - the polyatomic ion is put in between parentheses, and a subscript is used to indication the number of the ions that appear in the formula unit example: Ba(ClO 3 ) 2 CDO IB Chemistry SL32

Polyatomic Ions to Memorize Ammonium Hydrogen Carbonate (Bicarbonate) Carbonate Nitrate Hydroxide Sulfate Acetate (Ethanoate) Phosphate CDO IB Chemistry SL33

Types of Ionic Compounds Ionic compounds will always consist of one of the following combinations: a metal and a nonmetal a polyatomic ion and a nonmetal a metal and a polyatomic ion or two polyatomic ions CDO IB Chemistry SL34

Properties of Ionic Compounds High melting points that correlate with charges on ions Most ionic solids do not conduct electricity but molten ionic compounds do. Most ionic compounds dissolve in water CDO IB Chemistry SL35

Properties cont. Solutions of ionic compounds in water conduct electricity (electrolytes) In ionic substances, each ion has its own characteristics, and these are different from the characteristics of the atom from which the ion was derived (NaCl) CDO IB Chemistry SL36

Binary Compound Nomenclature 37 CDO IB Chemistry SL

Ionic Nomenclature Write the name of the cation. If the cation is a polyatomic ion, write the name of the polyatomic ion If the cation can have more than one possible charge, write the charge as a Roman numeral in parentheses. If the anion is an element, change its ending to -ide; If the anion is a polyatomic ion, simply write the name of the polyatomic ion. CDO IB Chemistry SL38

Examples Formula to Name NaCl MgCl 2 KBr CuCl CuCl 2 Al(NO 3 ) 3 CDO IB Chemistry SL39

Example Name to Formula CDO IB Chemistry SL40

White Board Practice CDO IB Chemistry SL41

Binary Molecular Nomenclature 42 CDO IB Chemistry SL

Nonmetals + nonmetals Name nonmetal further to the left of the periodic table first with no changes Name nonmetal further to the right of the periodic table second with the -ide suffix Use Greek prefixes to indicate the number of each one CDO IB Chemistry SL43

Greek prefixes NumberPrefix 1Mono 2Di 3Tri 4Tetra 5Penta 6Hexa 7Hepta 8Octa 9Nona 10Deca 44CDO IB Chemistry SL

Examples N 2 O 3 CO 2 P 2 O 5 CDO IB Chemistry SL45

Acids Binary acids – H with one other non metal name begins with hydro then add stem of nonmetal plus -ic end with acid Examples HCl – H 2 S - CDO IB Chemistry SL46

Oxyacids Take polyatomic suffix and convert change -ate to -ic change -ite to -ous Do not use hydro- in the beginning Examples H 2 SO 4 – H 2 SO 3 - CDO IB Chemistry SL47

Hydrates Some ionic compounds can have water molecules attached within the structure These compounds are termed hydrates and have properties distinct from the unhydrated form CDO IB Chemistry SL48

Naming Hydrates Hydrates are named by naming the ionic compound and then using a Greek prefix to indicate the number of water molecules followed by the word hydrate Example CuCl 2 5H 2 0 CDO IB Chemistry SL49

Formula Calculations 50 CDO IB Chemistry SL

Types of Formulas Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound. CDO IB Chemistry SL51

Empirical Formula Simplest whole number ratio of atoms in the compound All ionic formulas are empirical Molecular formulas are either equal to the empirical or a whole number multiple CDO IB Chemistry SL52

The composition of compounds Mole composition is the number of moles of each of the elements that make up the compound CO 2 - one mole of C and two moles of O Mass composition is the mass of each element in the compound CO g of C and 32.0 g of O CDO IB Chemistry SL53

Percent composition Equation x( Molar Mass of Element A) x 100 Molar Mass Compound Example Find the mass % of each element in CH 2 O (formaldehyde) CDO IB Chemistry SL54

White Board Practice Find the percent by mass of carbon in CO 2 CDO IB Chemistry SL55

Calculating Formulas 56 CDO IB Chemistry SL

Determination of Empirical formula Problem Solving Process: CDO IB Chemistry SL57

Example Example: A compound contains 63.6% N and 36.4% O, determine the compounds empirical formula 58CDO IB Chemistry SL

Example Determine the empirical formula for a compound which is 26.6% K, 35.4% Cr, 38.0% O CDO IB Chemistry SL59

White Board Practice What is the empirical formula of a compound which is 26.4% N, 5.66% H and 67.9 % C CDO IB Chemistry SL60

Molecular formula The actual number of each atom in a formula unit Consider acetylene and benzene both have the empirical formula CH acetylene is actually C 2 H 2 benzene is actually C 6 H 6 CDO IB Chemistry SL61

Molecular Formula from Empirical Molecular formula must be integral multiple of empirical formula Therefore the mass of the molecular formula must be the same integral multiple of the mass of the empirical formula. CDO IB Chemistry SL62

Example A compound has the following composition 20.0% C, 2.2 % H, 77.8 % Cl. The molar mass of the compound is 545 g/mol. What is the molecular formula of the compound CDO IB Chemistry SL63

White Board Practice A compound is composed f 1.65 g N and 3.78 g S, its molar mass is 184 g/mol, what is the molecular formula? CDO IB Chemistry SL64