ch 7.1 forming ions. review… cations are groups 1a, 2a, and 3a –they have positive charges....
TRANSCRIPT
Ch 7.1 Forming Ions
Review…
• Cations are Groups 1A, 2A, and 3A– They have positive charges.
• Anions are Groups 5A, 6A, and 7A– They have negative charges– They end in “ide”
• Majority of elements in Groups 4A and 8A do not usually form ions.
• These are called monatomic ions!
Ions of Transition Metals
• Some transition metals in Groups 1B-8B form more than one cation with different charges.
• Examples:– Iron forms Fe2+ and Fe3+
• Two methods of naming: – Stock System: Iron (II) ion and Iron (III) ion– Classical name: Ferrous ion and Ferric ion
*We will use the stock system.
Common Metal Ions with More than One Ionic Charge
Symbol Stock Name Classical Name
Cu+ Copper(I) ion Cuprous ion
Cu2+ Copper(II) ion Cupric ion
Fe2+ Iron(II) ion Ferrous ion
Fe3+ Iron(III) ion Ferric ion
*Hg22+ Mercury(I) ion Mercurous ion
Hg2+ Mercury(II) ion Mercuric ion
Pb2+ Lead(II) ion Plumbous ion
Pb4+ Lead(IV) ion Plumbic ion
Common Metal Ions with More than One Ionic Charge
Symbol Stock Name Classical Name
Sn2+ Tin(II) ion Stannous ion
Sn4+ Tin(IV) ion Stannic ion
Cr2+ Chromium(II) ion Chromous ion
Cr3+ Chromium(III) ion Chromic ion
Mn2+ Manganese(II) ion Manganous ion
Mn3+ Manganese(III) ion Manganic ion
Co2+ Cobalt(II) ion Cobaltous ion
Co3+ Cobalt(III) ion Cobaltic ion
Other Transition Metal Ions
• Some transition metals have only one charge and do not use a Roman numeral.
• Examples (Write on your periodic table!)– Silver: Ag+
– Cadmium: Cd2+
– Zinc: Zn2+
Polyatomic Ions• The names of most polyatomic anions
end in “-ite” or “-ate”
• The “-ite” ending indicates one less oxygen atom than the “-ate” ending
• Remember to use parentheses if more than one is needed.
Write the formula that will form between Ba and ClSolution:1. Write the positive ion of metal first, and then negative ion
Ba2+ Cl 2. Do the charges equal zero? NO!! 3. Use Criss-Cross method – write
subscripts
Ba2+ Cl1 BaCl2
Write the correct formula for the compounds containing the following ions:
1. Na+, S2-
2. Al3+, Cl-
3. Mg2+, N3-
4. Al3+, S2-
1. Na+, S2-
Na2S
2. Al3+, Cl-
AlCl3
3. Mg2+, N3-
Mg3N2
4. Al3+, S2-
Al2S3
Binary Compound: is composed of two elements and can be either
ionic or molecular.
Naming Binary Ionic Compounds
• To name a binary ionic compound, place the cation name first, followed by the anion name.
• Remember the anion ends in “-ide”• Examples:
– Cs2O– NaBr– CuO
Cesium OxideSodium BromideCopper(II) Oxide
Naming Compounds withPolyatomic Ions
• State the cation first and then the anion just as you did in naming binary ionic compounds.– KNO3
– Mg(ClO2)2
Potassium NitrateMagnesium Chlorite
Naming Binary Molecular Compounds
• Binary molecular compound: must be composed of two nonmetals
• Use prefixes to indicate the number and kind of atom in the compound
• Use the following general format:
1st name: prefix + element name2nd name: prefix + element name + “ide”
If there is only 1 of the 1st element, no prefix.
Prefixes in Covalent Compounds pg 228
Number of atoms
Prefix Number of atoms
Prefix
1 mono- 6 hexa-
2 di- 7 hepta-
3 tri- 8 octa-
4 tetra- 9 nona-
5 penta- 10 deca-
Anyone want a cold glass of dihydrogen monoxide?
Examples
• Name the following– CO
– CO2
– N2O
– Cl2O8
Carbon Monoxide
Carbon Dioxide
Dinitrogen Monoxide
Dichlorine Octoxide
Writing Formulas for Binary Molecular Compounds• Use the prefixes in the name to tell you
the subscript of each element in the formula.
• Then write the correct symbols for the two elements with the appropriate subscripts.
• The least electronegative element is written first
• Dinitrogen Tetroxide - N2O4
Examples
• Write formulas for the following:– Nitrogen Monoxide
– Carbon Tetrachloride
– Diphosphorous Pentoxide
NO
CCl4
P2O5
Naming Acids
• An acid is a compound that contains one or more hydrogen atoms and produces hydrogen ions (H+) when dissolved in water.
• All acids begin with hydrogen
• General Format: HnX
– “X” represents a monatomic or polyatomic anion.
– “n” represents the number of hydrogen ions
3 Rules for Naming Common Acids
• If the name of “X” ends in -ate:
____________-ic acid
• If the name of “X” ends in -ite:
____________-ous acid
• If the name of “X” ends in -ide:
hydro-__________-ic acid
Name these acids
• H2SO4
• HCl
• H2S
• HNO3
• HClO2
Sulfuric Acid
Hydrochloric Acid
Hydrosulfuric Acid
Nitric Acid
Chlorous Acid
Writing Formulas for Acids
• If the acid ends in –ic, then “X” ends in –ate
• If the acid ends in –ous, then “X” ends in –ite
• If the acid has hydro-______-ic, then “X” ends in –ide.
• The subscript on hydrogen is equal to the charge of “X”.
Write the Formula for the Following Acids
• Hydrobromic Acid
• Carbonic Acid
• Phosphoric Acid
• Sulfurous Acid
HBr
H2CO3
H3PO4
H2SO3
Homework
• 7.1 pg 251 #14, 15(a-d), 41
Ch 7.3 Using Chemical Formulas
The Mass of a Mole of an Element
• Molar Mass: is the atomic mass of an element expressed in grams/mole (g/mol).
• Carbon = 12.01 g/mol
• Hydrogen = 1.01 g/mol
• When dealing with molar mass, round off to two decimals. 12.011 g/mol 12.01 g/mol
The Mass of a Mole of a Compound• You calculate the mass of a molecule by
adding up the molar masses of the atoms making up the molecules.
• Example: H2O– H = 1.01 g x 2 atoms = 2.02 g/mol– O = 16.00 g x 1 atom = 16.00 g/mol
• Molar Mass of H2O = 2.02 g/mol + 16.00 g/mol = 18.02 g/mol
• This applies to both molecular and ionic compounds
• Find the molar mass of PCl3
– P = 30.97 g x 1 atom = 30.97 g/mol– Cl = 35.45 g x 3 atoms = 106.35 g/mol– PCl3 = 30.97 g + 106.35 g = 137.32 g/mol
• What is the molar mass of Sodium Hydrogen Carbonate (NaHCO3) ?– Na = 22.99 g x 1 atom = 22.99 g/mol– H = 1.01 g x 1 atom = 1.01 g/mol– C = 12.01 g x 1 atom = 12.01 g/mol– O = 16.00 g x 3 atoms = 48.00 g/mol– NaHCO3 = 22.99 + 1.01 + 12.01 + 48.00 = 84.01 g/mol
Converting Moles to Mass
• You can use the molar mass of an element or compound to convert between the mass of a substance and the moles of a substance.
• Mass (g) = # of moles x mass (g)
1 mole
Example: If molar mass of NaCl is 58.44 g/mol, what is the mass of 3.00 mol NaCl?
Mass of NaCl = 3.00 mol x 58.44g =
1 mol
175 g NaCl
Example 2: Moles to Mass
• What is the mass of 9.45 mol of Aluminum Oxide (Al2O3)?
• Find molar mass of Al2O3
= 101.96 g/mol
• Mass = 9.45 mol Al2O3 x 101.96 g Al2O3
1 mol Al2O3
= 964 g Al2O3
Converting Mass to Moles• You can invert the conversion factor to find
moles when given the mass.
• Moles = mass (g) x 1 mole
mass (g)
Example: If molar mass of Na2SO4 142.05 g/mol, how many moles is 10.0 g of Na2SO4?
Moles of Na2SO4 = 10.0 g x 1 mol =
142.05 g= 0.0704 mol Na2SO4
Example 2: Mass to Moles
• How many moles are in 75.0 g of Dinitrogen Trioxide?
• Find molar mass of N2O3
= 76.02 g/mol
• Moles = 75.0 g N2O3 x 1 mole =
76.02 g
N2O3
0.987 mol N2O3
Percent Composition
• Percent Composition: the relative amount of the elements in a compound.
• Also known as the percent by mass
• It can be calculated in two ways:– Using Mass Data– Using the Chemical Formula
% mass of element= mass of element x100% mass of compound
Example• When a 13.60 g sample of a compound containing
Mg and O is decomposed, 5.40 g O is obtained. What is the % composition of this compound?
Mass of compound: 13.60 g
Mass of oxygen: 5.40 g O
Mass of magnesium: 13.60 g - 5.40 g = 8.20 g Mg
% Mg = 8.20 g Mg x 100% =
13.60 g
% O = 5.40 g O x 100% =
13.60 g
60.3%
39.7%
• Find the percent composition of Cu2S.
• Find mass of Cu and S– Cu = 63.55 x 2 = 127.10 g– S = 32.07 g
• Find mass of Cu2S
– 127.10 g + 32.07 g = 159.17 g
% Composition – Cu = 127.10 g x 100% =
159.17 g– S = 32.07 g x 100% =
159.17 g
79.85%
20.15%
• Find the percentage by mass of water in the hydrate Na2CO310H2O
• Find the mass of 10H2O
– H2O = 10 mol x 18.02 g/mol = 180.2 g
• Find the mass of Na2CO310H2O
– Na2CO3 = 1 mol x 105.99 g/mol =105.99 g
– 105.99 g + 180.2 g = 286.2 g
• % By Mass of Water – H2O = 180.2 g H2O x 100% =
286.2 g Na2CO310H2O
62.96%
Homework
• 7.3 pg 253 #30-33
Ch 7.4Determining Chemical Formulas
Empirical Formulas
• Empirical Formula: shows the smallest whole-number ratio of the atoms of the elements in a compound.
• Example: – The Empirical Formula for Hydrogen Peroxide
(H2O2) is HO with a 1:1 ratio.
– The Empirical Formula for Carbon Dioxide (CO2) is CO2 with a 1:2 ratio.
Determining the Empirical Formula of a Compound
• A compound is found to contain 25.9% Nitrogen and 74.1% Oxygen. What is the Empirical Formula of the compound?
• 25.9 g N x 1 mol N = 14.01 g N
• 74.1 g O x 1 mol O = 16.00 g O
• N1.85O4.63 = N1O2.5 = N2O5
1.85 mol N
4.63 mol O
Molecular Formulas• Molecular Formula: tells the actual number
of each kind of atom present in a molecule of a compound
• Example: – The Molecular Formula for Hydrogen Peroxide is
H2O2.
– The Molecular Formula for Carbon Dioxide is CO2
• It is possible to find the Molecular Formula using the Empirical Formula if you know the molar mass of the compound.
Finding the Molecular Formula• Calculate the molecular formula of a
compound whose molar mass is 60.0 g/mol and empirical formula is CH4N
• Step 1: Find the empirical formula molar mass– 12.01 + (4 x 1.01) + 14.01 = 30.06 g/mol
• Step 2: Divide molar mass by EF molar mass– 60.0 g/mol = 1.99 2
30.06 g/mol
• Step 3: Multiply empirical formula by 2– CH4N x 2 = C2H8N2
Homework
• 7.4 pg 253 #36-38