CHM104 -- Exam 2
A chemical equation tells us what substances react (reactants) and what substances are formed (products)
(+) used when there is two or more products or reactants Δ heat is used to start the reaction (s) the compound is a solid (l) the compound is a liquid (g) the compound is a gas (aq) aqueous, the compound is dissolved in water
Combination Reaction (synthesis): two or more elements combine to form one product 2Mg + O₂ ---> ??? 2Na + Cl₂ ---> ??? SO₃ + H₂O ---> ??? Ca + Cl₂ ---> ???
A + B ---> AB 2MgO 2NaCl H₂SO₄ CaCl₂
Single Replacement: one element takes the place of a different element on a reacting compound Zn + 2HCl ----> ??? Fe + CuSO₄ ---> ??? Cu + 2AgNO₃ ---> ???
A + BC ---> AC + B ZnCl₂ + H₂ FeSO₄ + Cu Cu(NO₃)₂ + 2Ag
Double Replacement: the two positive ions in the reacting compounds exchange places. AgNO₃ + NaCl ---> ??? ZnS + HCl ---> ??? BaCl₂ + K₂SO₄ ---> ???
AB + CD ---> AD + CB AgCl + NaNO₃ ZnCl₂ + H₂S BaSO₄ + 2KCl
Decomposition Reaction: one substance splits into two or more simpler substances 2HgO ---> ??? 2KClO₃ ---> ??? Fe₂S₃ ---> ???
AB ---> A + B 2Hg + O₂ 2KCl + 3O₂ 2Fe + 3S
How to Balance a Chemical Equation: 1. Make sure that the same number of atoms (for each element) are on both sides of the equation. 2. Treat the chemical reaction as an algebraic equation with the arrow as the equal sign 3. Coefficients in front of the compounds are used to balance the equation. 4. The total charge of all the compounds on both side of the equation must be the same
EXAMPLE: Step 1: Write an equation using the correct formulas of the reactants and products. C₂H₆O + O₂ --> H₂O + CO₂ Step 2: Count the atoms of each element in the reactants and products Atoms of C: 2 --> 1 (not balanced) Atoms of H: 6 --> 2 (not balanced) Atoms of O: 3 --> 3 (balanced) Step 3: Use coefficients to balance each element. C₂H₆O + 3O₂ --> 3H₂O + 2CO₂ Step 4: Check the final equation to confirm it is balanced Atoms of C: 2--> 1 (balanced) Atoms of H: 6 --> 2 (balanced) Atoms of O: 3 --> 3 (balanced)
Electron and Molecular Geometries
linear geometry: 2 electron groups around the central atom will be placed on opposite sides of the central atom. bond angle become 180 degrees trigonal planar geometry: 3 electron groups around the central atom, occupying the shape of a triangle around the central atom. bond angle is 120 degrees tetrahedral geometry: 4 electron groups around the central atom, occupying the position in the shape of a tetrahedron around the central atom. bond angle is 109.5 degrees
Rules for Naming and Writing Chemical Formulas: Ionic
- the name of the METAL ion written FIRST - the name of the NONMETAL ion written SECOND using the first syllable of its element name, followed by "ide" - has a space separating the name of the metal and nonmetal
Atoms form octets...
- to become more stable -by losing, gaining, or sharing electrons - by forming *ionic* or *covalent bonds*
Rules for assigning oxidation states
1) Standard state is 0 2) Sum of oxidation states in a compound must be 0 or the ion's charge 3) Group 1 has +1 and group 2 has +2 4) Fluorine has -1 5) Hydrogen has +1 or 0 when bound to carbon (can also be -1 if less electronegative than carbon) 6) Oxygen has -2 7) Halogens (Group 7A) have -1 and oxygen family has -2. 8) Group 6A has -2 9) Group 5A has -3 *oxidation states do not have to be whole numbers
Balancing Chemical Reactions 1. Na₃PO₄ + MgCl₂ --> NaCl + Mg₃(PO₄)₂ 2. Fe₂O₃ + C --> Fe + CO₂ 3. Al + FeO --> Fe + Al₂O₃ 4. Al + H₂SO₄ --> Al₂(SO₄)₃ + H₂
1. 2Na₃PO₄ + 3MgCl₂ --> 6NaCl + Mg₃(PO₄)₂ 2. Fe₂O₃ + C --> Fe + CO₂ 3. 3. Al + FeO --> Fe + Al₂O₃ 4. Al + H₂SO₄ --> Al₂(SO₄)₃ + H₂
The geometric figures have characteristic angles that are called...
bond angles
When writing an IONIC compound...
the metal if FIRST, the nonmetal is LAST
When a METAL interacts with a NONMETAL, it can TRANSFER one or more electrons to the nonmetal...
the metal then becomes a CATION the nonmetal becomes an ANION
In an oxidation-reduction reaction: Example: 4Fe + 3O₂ ---> 2Fe₂O₃
- electrons are transferred from one substance to another - if 1 substance loses electrons, another substance must gain electrons - energy is provided to us from food - electrical energy is provided in batteries - iron rusts
names of common acids
SLIDE 25 PPT4
Rules or the VSEPR Model
- electron pairs around the central atom stay as far apart as possible - consider non-bonding (lone pairs) as well as bonding electrons - electron pairs in single, double and triple bonds are treated as single electron clouds - the shape formed by the four electron pairs is called a tetrahedron. The electron pairs are said to have the tetrahedral shape - in water, H2O, two of the corners of the tetrahedron are occupied by hydrogens. This is what gives the water molecule its bent shape.
# of covalent bonds a nonmetal forms = # of electrons it needs to acquire a stable electron configuration
1A: 1 bond 3A: 3 bonds 4A: (8e-) -4(group #) = 4 bonds 5A: (8e-) - 5(group #) = 3 bonds 6A: (8e-) - 6(group #) = 2 bonds 7A: (8e-) - 7(group #) = 1 bond 8A: (8e-) - 8(group #) = 0 bonds
Steps for Writing Formulas for Ionic Compounds Ex: aluminum and oxygen
Al O 1. write symbol for metal & the charge Al³+ 2. write symbol for nonmetal & the charge (found in periodic table) O²- 3. "cross over" charges Al₂ O₃ 4. Check that sum of the charges of the cation = sum up charges of the anion. cations: 2(3+) = 6+ anions: 3(2-) = 6- +6 + -6 = 0 The charges cancel.
Prefixes are used.. - to indicate the # of protons present for each element in the compound -because 2 nonmetals can form 2 or more different compounds
Prefixes Used in Naming Molecular Compounds 1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca
Combustion: a carbon-containing compound that is the fueled burns in oxygen from the air to produce carbon dioxide, water, and energy in the form of heat for a flame. CH₄ + 2O₂ --> ??? 2C₂H₆ + 7O₂ ---> ??? CH₄ + 2O₂ --Δ--> ???
Reaction of organic compounds with oxygen to form carbon dioxide. *only way to recognize this.... on the product side; you are only making CO₂ & H₂O CO₂ + 2H₂O + energy 4CO₂ + 6H₂O CO₂ + 2H₂O + energy
What does VSEPR stand for?
Valence Electron Pair Repulsion
Some Common Molecular Compounds Formula: CS₂ CO₂ NO N₂O SO₂ SO₃ SF₆
Name: Carbon disulfide Carbon dioxide Nitrogen oxide Dinitrogen oxide Sulfur dioxide Sulfur dioxide Sulfur trioxide Sulfur hexafluoride
Naming and Writing Chemical Formulas: EXAMPLES Nonmetals: 1. N³- 2. P³- 3. O²- 4. S²- 5. F- 6. Cl- 7. Br- 8. I- Metals: 1. Li+ 2. Na+ 3. K+ 4. Mg²+ 5. Ca²+ 6. Ba²+ 7. Al³+
Nonmetals: 1. Nitride 2. Phosphide 3. Oxide 4. Sulfide 5. Fluoride 6. Chloride 7. Bromide 8. Iodide Metals: 1. Lithium 2. Sodium 3. Potassium 4. Magnesium 5. Calcium 6. Barium 7. Aluminum
Compounds are IONIC if it contains....
metals & nonmetals
Names and Formulas of Some Common Polyatomic Ions Formula of Ion Hydrogen: OH- Nitrogen: NH₄+ NO₃- NO₂- Chlorine: ClO₄- ClO₃- ClO₂- ClO- Carbon: CO₃²- HCO₃- CN- C₂H₃O₂- Sulfur: SO₄²- HSO₄- SO₃²- HSO₃- Phosphorous: PO₄³- HPO₄²- H₂PO₄- PO₃³-
Name of Ion: Hydrogen: Hydroxide Nitrogen: Ammonium Nitrate Nitrite Chlorine: Perchlorate Chlorate Chlorite Hypochlorite Carbon: Carbonate Hydrogen carbonate (or bicarbonate) Cyanide Acetate Sulfur: Sulfate Hydrogen sulfate (or bisulfate) Sulfite Hydrogen sulfite (bisulfite) Phosphorous: Phosphate Hydrogen phosphate Dihydrogen phosphate Phosphite
Some Ionic Compounds That Contain Polyatomic Ions Formula: BaSo₄ CaCo₃ Ca₃(PO₄)₂ CaSO₄ AgNO₃ NaHCO₃ Zn₃(PO₄)₂ K₂CO₃ Al₂(SO₄)₃ AlPO₄ MgSO₄
Name: Barium sulfate Calcium carbonate Calcium phosphate Calcium sulfate Silver nitrate Sodium bicarbonate or sodium hydrogen carbonate Zinc phosphate (no roman numeral because this is a transition metal) Potassium carbonate Aluminum sulfate Aluminum phosphate Magnesium sulfate
Compounds are COVALENT if it contains...
nonmetal & nonmetal
Rules for Redox Reactions
sum of the oxidation #'s = charge of the compound if something is iodized, that means the oxidation # gets more positive. If something is reduced, the oxidation # gets more negative
Balancing Chemical Equations: Detailed Example 1. Write a balanced equation for the reaction between solid cobalt(III) oxide and solid carbon to produce solid cobalt and carbon dioxide gas. 2. Write a balanced equation for the reaction between solid silicon dioxide and solid carbon to produce solid silicon carbide and carbon monoxide gas. 3. Write a balanced equation for the combustion of gaseous ethane (C₆H₆), a minority component of natural gas, in which it combines with gaseous oxygen to form gaseous carbon dioxide and gaseous water. 4. White a balanced equation for the reaction between aqueous lead(II) nitrate and aqueous potassium chloride to form solid lead(LL) chloride and aqueous potassium nitrate.
1. Co₂O₃ + C ---> Co + CO₂ Balanced: 2Co₂O₃ + 3C ---> 4Co + 3CO₂ 2. 3. 4.
Rules for assigning Oxidation States
1. Free elements have an oxidation state = 0 2. Monoatomic ions have an oxidation state equal to their charge 3. (a) The sum of the oxidation states of all the atoms in a neutral compound = 0 (b) The sum of the oxidation states of all the atoms in a polyatomic ion equals the charge on the ion 4. (a) Group I metals have an oxidation state of +1 in all their compounds. (b) Group II metals have an oxidation state of +2 in all their compounds 5. In their compounds, nonmetals have oxidation states according to the table below Fluorine = -1 Hydrogen = +1 Oxygen = -2 Group 7A = -1 Group 6A = -2 Group 5A = -3
Some Ionic Compounds of Metals That Form Two Kinds of Positive Ions: 1. FeCl₂ 2. Fe₂O₃ 3. Cu₃P 4. CrBr₂ 5. SnCl₂ 6. PbS₂ 7. BiF₃
1. Iron (II) chloride 2. Iron (III) oxide 3. Copper (I) phosphide 4. Chromium (II) bromide 5. Tin (II) chloride 6. Lead (IV) sulfide 7. Bismuth (III) fluoride
Naming and Writing Chemical Formulas: EXAMPLES 1. Fe Cl₂ 2. Ca O 3. Tin Chloride
1. Iron Chloride 2. Calcium Oxide 3. SnCl₄ -- tin (IV) chloride OR SnCl₂ -- tin (II) chloride
Writing Formulas for Chemical Compounds. Name if it is an IONIC or COVALENT chemical compound. 1. potassium & sulfur: 2. calcium & oxygen: 3. aluminum & nitrogen: 4. nitrogen & iodine 5. phosphorous & chlorine 6. phosphorous & sulfur
1. K₂S = ionic 2. CaO = ionic 3. AlN = ionic 4. NI₃ = covalent 5. PCl₃ = covalent 6. P₂S₃ = covalent
Chemical reactions can be classified as... 1. 3Ba + N₂ ---> Ba₃N₂ 2. K₂CO₃ ---> K₂O + CO₂ 3. Hg + 2HCl ---> HgCl₂ + H₂ 4. PbCl₂ + K₂SO₄ ---> 2KCl + PbSO₄ 5. CH₄ + 2O₂ ---> CO₂ + 2H₂O + energy
1. combination reactions 2. decomposition reactions 3. single replacement reactions 4. double replacement reactions 5. combustion reactions
Ionic Bonds - exchange of electrons - metal/non-metal - 3-D units extended - high melting point/boiling point - brittle (behaves like glass, shatter) - e.g. NaCl - melt, solution conduct electricity (make electric current)
Covalent Bonds - SHARING electrons - non-metal/non-metal - molecular (low melting point / boiling point) - e.g.: CO₂, Cl₂ - Macromolecular (high mp/bp) - E.g.: C (diamond), SiO₂ - Non conductors
Assign an Oxidation State to each atom in each element, ion, or compound. a. Cl₂ b. Na+ c. KF d. CO₂ e. SO₄²- f. K₂O₂
a. Since Cl₂ is a free element, the oxidation state of both Cl atoms is 0. b. Since Na+ is a monoatomic ion, the oxidation state of the Na+ ion is +1 c. The oxidation state of K is +1. The oxidation state of F is -1. Since this is a neutral compound, the sum of the oxidation states is 0 d. The oxidation state of oxygen is -2. The oxidation state of carbon must be deduced using rule 3, which says that the sum of the oxidation states of all the atoms must be 0 e. the oxidation state of oxygen is -2. We would ordinarily expect the oxidation state of S to be -2. However, if there were the case, the sum of the oxidation states would not equal the charge of the ion. Since O is higher on the list than S, it takes priority and we compute the oxidation state of sulfur by setting the sum of all of the oxidation states equal to -2 (the charge of the ion) f. The oxidation state of potassium is +1. We would ordinarily expect the oxidation state of O by setting the sum of all the oxidation states equal to 0
Name of Common Polyatomic Anions
end in a "ate" NO₃- = nitrate PO₄³- = phosphate with one oxygen less, end in "ite" NO₂- = nitrite PO₃³- = phosphite with hydrogen attached, use prefix hydrogen (or bi) HCO₃- = hydrogen carbonate (bicarbonate) HSO₃- = hydrogen sulfite (bisulfite) NOTE: the difference between the ending "ate" and "ite" is one oxygen atom!
bases with OH- ions are named as the ________ of the metal in the formula
hydroxide NaOH = sodium hydroxide KOH = potassium hydroxide Ba(OH)₂ = barium hydroxide Al(OH)₃ = aluminum hydroxide Fe(OH)₃ = iron (III) hydroxide Ca(OH)₂ = calcium hydroxide LiOH = Lithium hydroxide
Chemical Formula of Ionic Compound = the element symbols and subscripts
in the formula of an ionic compound: positive ions + negative ions = 0 (ALWAYS) this makes the charges balanced
covalent bonds = SHARING of electrons
ionic bonds = TRANSFER of electrons
