Presentation on theme: "Chapter 7 Chemical Formulas & Chemical Compounds"— Presentation transcript:
1Chapter 7 Chemical Formulas & Chemical Compounds 7.1 Chemical Names & Formulas
2Ions Cation: A positive ion Mg2+, NH4+ Anion: A negative ion Cl-, SO42-Ionic Bonding: Force of attraction between oppositely charged ions.
3Predicting Ionic Charges Groups :Many transition elements have more than one possible oxidation state.Iron (II) = Fe2+Iron (III) = Fe3+
4Predicting Ionic Charges Groups :Some transition elements have only one possible oxidation state.Zinc = Zn2+Silver = Ag1+
5Formula Writing for Binary Ionic Compounds criss-cross the oxidation numbers to balance out the charge.Magnesium BromideMg Br – 1Mg1Br2MgBr2Calcium SulfideCa + 2 S – 2Ca2S2CaS
6Writing Ionic Compound Formulas Example: Iron (III) chloride1. Write the formulas for the cation and anion, including CHARGES!Fe3+Cl-2. Check to see if charges are balanced.33. Balance charges, if necessary, using subscripts.Not balanced!
7Naming Ionic Compounds 1. Cation first, then anion2. Monatomic cation = name of the elementCa2+ = calcium ion3. Monatomic anion = root + -ideCl- = chlorideCaCl2 = calcium chloride
8Naming Ionic Compounds Metals with multiple oxidation statessome metal forms more than one cationuse Roman numeral in namePbCl2Pb2+ is cationPbCl2 = lead (II) chloride
9Elements with Multiple Oxidation Numbers Manganese II Mn+2Manganese III Mn+3Manganese VII Mn+7Cobalt II Co+2Cobalt III Co+3Gold I Au+1Gold III Au+3Nickel II Ni+2Nickel III Ni+3Nickel IV Ni+4**Silver Ag+1**Zinc Zn+2**Cadmium Cd+2Copper I Cu+1Copper II Cu+2Iron II Fe+2Iron III Fe+3Mercury I Hg+1Mercury II Hg+2Lead II Pb+2Lead IV Pb+4Tin II Sn+2Tin IV Sn+4Chromium II Cr+2Chromium III Cr+3Chromium VI Cr+6
10♥ Poly Atomic Ions to Know and Love ♥ Name Formula Name FormulaAcetateC2H3O2-1 (CH3COO -1)HypochloriteClO-1DichromateCr2O7-2ChloriteClO2-1AmmoniumNH4+1ChlorateClO3-1NitrateNO3-1PerchlorateClO4-1NitriteNO2-1CyanideCN-1HydroxideOH-1CarbonateCO3-2PhosphatePO4-3ChromateCrO4-2
11♥ More Poly Atomic Ions to Know and Love ♥ Name Formula Name FormulaSulfiteSO3-2Hydrogen CarbonateHCO3-1SulfateSO4-2Hydrogen PhosphateHPO4-2Hydrogen SulfiteHSO3-1Hydrogen SulfateHSO4-1PermanganateMnO4-1OxalateC2O4-2HydroniumH3O+SilicateSiO3-2PeroxideO2-2PhosphitePO3-3BromateBrO3-1ArsenateAsO4-2
12Naming Compounds with Polyatomic Ions Formula Name(NH4)2SO4 ammonium sulfateZnCO3 zinc carbonateNH4Br ammonium bromideLi2CO3 lithium carbonate* Polyatomic & monatomic cation names remain the same, monatomic anions change their ending to –ide.
13Writing Ionic Compound Formulas Example: Barium nitrateBa2+( )NO3-21. Write the formulas for the cation and anion, including CHARGES!Not balanced!2. Check to see if charges are balanced.3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
14Writing Ionic Compound Formulas Example: Ammonium sulfate( )NH4+SO42-21. Write the formulas for the cation and anion, including CHARGES!Not balanced!2. Check to see if charges are balanced.3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
15Writing Ionic Compound Formulas Example: Aluminum sulfideAl3+S2-231. Write the formulas for the cation and anion, including CHARGES!Not balanced!2. Check to see if charges are balanced.3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
16Writing Ionic Compound Formulas Example: Magnesium carbonateMg2+CO32-1. Write the formulas for the cation and anion, including CHARGES!2. Check to see if charges are balanced.They are balanced!3. Simplify to a formula unit.
17Writing Ionic Compound Formulas Example: Zinc hydroxideZn2+( )OH-21. Write the formulas for the cation and anion, including CHARGES!Not balanced!2. Check to see if charges are balanced.3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
18Writing Ionic Compound Formulas Example: Aluminum phosphateAl3+PO43-1. Write the formulas for the cation and anion, including CHARGES!They ARE balanced!2. Check to see if charges are balanced.
19Chemical Formula Chemical Name More Examples…Chemical Formula Chemical NameCr2O3Cr2OCuSO4Ni(OH)2Cr2(C2O4)3Cu2SCuSchromium (III) oxidechromium (I) oxidecopper (II) sulfatenickel (II) hydroxidechromium (III) oxalatecopper (I) sulfidecopper (II) sulfide
20HydratesHydrate – when a water molecule (s) are chemically bonded to the ionic compound.Normal ionic naming protocol are used, then followed by the word “hydrate.”Prefixes are added to indicate the number of water molecules when naming hydrates.
21Hydrate Prefixes # of water molecules prefix 1 mono- 6 hexa- 2 di- 7 hepta-3tri-8octa-4tetra-9nona-5penta-10deca-
22Hydrates Example: MgBr2 ∙ 6H2O Magnesium bromide hexahydrate The “ ∙ ” means “loosely bonded”Hygroscopic - easily absorb water molecules from the air.Deliquescent- very hygroscopic; takes out water from the air to dissolve completely to form a liquid solution.Anhydrous – when all of the water has been removed.
23Naming Binary Covalent Compounds Compounds between two nonmetalsFirst element in the formula is named first.Second element is named as if it were an anion.Use prefixesOnly use mono on second elementP2O5 =diphosphorus pentoxideCO2 =carbon dioxideCO =carbon monoxideN2O =dinitrogen monoxide
24Acids always begin with Hydrogen AnionFormulaNameCl-1HClHydrochloric AcidBr-1HBrHydrobromic AcidSO4-2H2SO4Sulfuric AcidSO3-2H2SO3Sulfurous AcidNO3-1HNO3Nitric AcidCN-1HCNHydrocyanic AcidPO4-3H3PO4Phosphoric Acid
25Bases Cation Formula Name Na+1 NaOH Sodium Hydroxide K+1 KOH Potassium HydroxideNH4+1NH3Ammonia
26Organic CompoundsOrganic compounds are named using a different set of rules.The simplest group is the hydrocarbons. These compounds are composed solely of the elements carbon and hydrogen.Carbon atoms can link to each other in chains and in rings.
27The stem of the compound name is then chosen from the following table: Naming HydrocarbonsThe stem of the compound name is then chosen from the following table:# of carbon atomsprefix# of carbon atoms1meth-6hexa-2eth-7hepta-3prop-8octa-4but-9nona-5penta-10deca-
28Hydrocarbons: Alkanes These molecules have the generic formula: CnH2n+2They contain all single bonds.CH4methaneC2H6ethaneC3H8propaneC4H10butaneC5H12pentaneC6H14hexane
29Hydrocarbons: Alkenes These molecules have the generic formula:CnH2nThey contain double bonds between carbon atoms.C2H4etheneC3H6propeneC4H8buteneC5H10penteneC6H12hexene
30Hydrocarbons: Alkynes These molecules have the generic formula:CnHnThey contain triple bonds between carbon atoms.C2H2ethyneC3H3propyneC4H4butyneC5H5pentyneC6H6hexyne
31Chapter 7 Chemical Formulas & Chemical Compounds 7.2 Oxidation Numbers
32Oxidation NumbersOxidation Number – numbers assigned to atoms composing a compound or ion that indicate the general distribution of electrons among bonded atoms
34Chapter 7 Chemical Formulas & Chemical Compounds 7.3 Using Chemical Formulas
35Molar MassThe mass of 1 mole of a pure substance is called its Molar Mass.Ex: Molar mass of Iron is g/molWhat is the molar mass of Platinum?g/mol
36Molar MassThe molar mass depends on the particles that compose the compound. If your element exists as a molecule, i.e. BrINClHOF, one mole of these particles contains 2 moles of the element as an atom.Determine the molar mass of oxygen molecules (O2)(16.00 g/mol) x (2 atoms) = g/molThe molar mass of oxygen molecules (O2) is twice the molar mass of oxygen atoms!
37Formula MassThe molar mass of a compound is the mass of the atomic mass units of one molecule.This takes into consideration the number of atoms of each element in a compound.Formula Mass is calculated the same way as molar mass except it is measured in amu, instead of g/mol.
38Calculating Formula Mass Calculate the formula mass of magnesium carbonate, MgCO3.(16.00) =84.32 amu
39Steps for Calculating Molar Mass for Compounds List the elementsDetermine how many atoms of eachIdentify the atomic masses from the periodic tableMultiply how many atoms by the respective atomic massAdd up the totals for the Molar Mass
40Practice H2O H 2 x 1.008 = 2.016 O 1 x 15.99 = 15.99 18.006 NaCl Na 1 x = 22.9Cl 1 x = 35.4558.35g/molg/molK2OK 2 x = 78.2O 1 x = 15.9994.19C6H12O6C 6 x = 72.06H x =O 6 x = 95.94g/molg/mol
41Calculating Percentage Composition Calculate the percentage composition of magnesium carbonate, MgCO3.(16.00) = amu100.00
42*Must also find molar mass of H2O Mass PercentSo…. In one mole of H2O, how many grams of Hydrogen are there?2 mol H x g H = g H in 1 mol H2O 1 mol HWhat % of Hydrogen, by mass, is in H2O?2.016 g H x = % H18 g H20*Must also find molar mass of H2OWhat % of Oxygen, by mass is in H2O?
44Formulas molecular formula = (empirical formula)n [n = integer] Empirical formula: the lowest whole number ratio of atoms in a compound.Molecular formula: the true number of atoms of each element in the formula of a compound.molecular formula = (empirical formula)n[n = integer]molecular formula = C6H6 = (CH)6empirical formula = CH
45FormulasFormulas for ionic compounds are ALWAYS empirical (lowest whole number ratio). Often, these are called formula units.Examples:NaClMgCl2Al2(SO4)3K2CO3
46FormulasFormulas for molecular compounds MIGHT be empirical (lowest whole number ratio).Molecular:H2OC6H12O6C12H22O11Empirical:H2OCH2OC12H22O11
47Chapter 7 Chemical Formulas & Chemical Compounds 7.4 Determining Chemical Formulas
48Empirical Formula Determination Base calculation on assumption of 100 grams of compound.Determine moles of each element in 100 grams of compound.Divide each value of moles by the smallest of the values.Multiply each number by an integer to obtain all whole numbers.
49Empirical Formula Determination Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula of adipic acid?
50Empirical Formula Determination (part 2) Divide each value of moles by the smallest of the values.Carbon:Hydrogen:Oxygen:
51Empirical Formula Determination (part 3) Multiply each number by an integer to obtain all whole numbers.Carbon: 1.50Hydrogen: 2.50Oxygen: 1.00x 2x 2x 2352Empirical formula:C3H5O2
52Finding the Molecular Formula The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?1. Find the formula mass of C3H5O23(12.01 g) + 5(1.01) + 2(16.00) = g
53Finding the Molecular Formula The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?2. Divide the molecular mass by the mass given by the emipirical formula.3(12.01 g) + 5(1.01) + 2(16.00) = g
54Finding the Molecular Formula The empirical formula for adipic acid is C3H5O2. The molecular mass of adipic acid is 146 g/mol. What is the molecular formula of adipic acid?3. Multiply the empirical formula by this number to get the molecular formula.3(12.01 g) + 5(1.01) + 2(16.00) = g(C3H5O2) x 2 =C6H10O4
55Determining Chemical Formulas from Mass Percents A sample has been analyzed, here are the results:18.8 % Na29.0 % Cl52.2 % OHow can you determine the chemical formula?
56Step 1: Assume a 100 g sample.Then, your percent quantities become gram (mass) quantities.18.8 g Na , g Cl & g OStep 2: Convert those masses to moles.18.8 g Na x 1 mol Na = mol Na23 g Na29.0 g Cl x 1 mol Cl = mol Cl35.5 g Cl52.2 g O x 1 mol O = mol O16 g O
57Step 3: Since your empirical formula is in small, whole number ratios, divide your mole amounts by the smallest mole quantity.0.817 mol Na / = mol Na0.817 mol Cl / = mol Cl3.26 mol O / = ≈ 4.00 mol OStep 4: Use these values as subscripts in your formulaNa1Cl1O4 ≈ NaClO4
58Step 5: In the event the chemical formula is not the same as the empirical formula, you need the molar mass of the desired compound and you must compare it to the molar mass of the empirical formula.Step 6: Divide the given molar mass by the empirical molar mass to get the multiple quantity.Step 7: Multiply each subscript in the formula by that multiple quantity.
59Ex: MM of molecular formula = 180 g/mol Using steps 1-4, you found that the empirical formula is CH2O.Find the molar mass of the empirical formula: MM EF = 30 g/molDivide MM MF / MM EF to get a whole number.Ex: 180 / 30 = 6C1x6 H2x6 O1x6C6H12O6
60Practice Problems:A sample has been analyzed to be % C, 0.84 % H & 89.12% Cl. Find the Empirical Formula.A compound’s empirical formula has been determined to be HF. The compound’s molar mass is 40 g/mol. What is its chemical formula?A compound’s empirical formula has been determined to be CH2. The compound’s molar mass is 42 g/mol. What is its chemical formula?