Description
Chapter 1
Matter – Anything that occupies space and has mass.
Mass – a measure of the quantity of matter.
The interaction of mass with gravity creates weight.
Energy – the capacity to move an object or transfer heat.
Pure Substance – always has the same chemical composition no matter its origin. Mixture – Two or more substances that may vary in composition. - You can separate a mixture into their component pure substances. This can be done physically, by grinding/dissolving/filtering.
- Homogeneous Mixture AKA Solution – uniform composition throughout. Most mixtures are dissolved in water and are often clear. Each sample, no matter the size, would have the same components in the same proportions.
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- Heterogeneous Mixture – Not uniform throughout. Different samples will have different proportions of components.
- If the material can be separated, them it is a mixture, if not, it is a pure substance.
- If the substance can be broken down, it is a compound, if not, it is an element
- If the element conducts electricity, it is a metal, if not, it is a nonmetal. - Not all solutions are liquids. Solid solutions are called alloys.
There are two types of pure substances: Elements and Compounds Element – a substance that cannot be broken down into other simpler substances even by chemical reaction.
- An atom is the smallest unit of an element that has the chemical properties of that element.
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- Molecule – Two or more atoms bound together in a discrete arrangement. Molecules can also be formed by the combination of only one element. Ex) O2 Don't forget about the age old question of What does survival of the fittest state about every state?
- Element symbols with subscripts represent a ratio of elements in a compound.
Periodic Table – Columns of the table house groups/families of elements that share comparable properties.
- 2 main categories: Metals and Nonmetals
- Metals – shiny/conductive/ductile/malleable
- Nonmetals – dull/poor conductors/brittle
Compound – a substance made up of two or more elements combined in definite proportions.
- Compounds have different properties than their component elements. Chemical Formula – describes the composition of a compound using symbols for the elements that make the compound.
- Subscripts how the relative proportions of the elements in the compound. If there is no subscript, the subscript is assumed to be one. Physical State – a form that matter can take. Solid/Liquid/Gas Don't forget about the age old question of What are the sub-areas of linguistics?
- Solid – Fixed shape
- has its own volume
- no volume change under pressure
- particles are fixed in place and are in a regular array
(Crystalline).
- Liquid – takes the shape of its container
- has its own volume
- slight volume change under pressure
- particles are randomly arranged and move/bump into each
other
- Gas - takes the shape of its container and fills it
- has the volume of the container
- large volume change under pressure
- particles are widely separated and move independently
Symbols for Physical States
- Aqueous (aq)
- Solid (s)
- Liquid (l)
- Gas (g)
Aqueous Solution (aq) – a solution in which a substance is dissolved in water. Solids – Crystalline solids have a regular ordered structure. Amorphous solids have no ordered structure.
Physical Properties – can be measured without changing the identity of the substance and are often easily reversed. Ex) Color/odor/density/temperature/mass/volume/conductivity/malleability/ductility Chemical Properties – how something reacts with something else and changes the identity of the substance. Ex) flammability/color change/corrosiveness/combustion/reactivity Don't forget about the age old question of What is the state of membrane in the fluid mosaic model?
Intensive Properties – independent of the amount of substance. Ex) Color Extensive Properties – depend on the amount of substance. Ex) Energy released upon combustion/mass/volume/length
Changes of state are always physical.
Energy – Energy Units
- SI unit of hear = Joule (J) – 1J = (1kg X 1m^2)/S^2)
- Kinetic Energy = (1/2)mv^2
- Calorie (cal) – the quantity of energy (heat) needed to raise3 the temperature of 1g of water by 1 degree Celsius
- 1 cal = 4.184J
- 1 kcal = 1000 cal = 1 Cal
Heat and Specific Heat
Heat (q) = the energy transferred between a system and its surroundings as a result of temperature difference.
Specific Heat (s or SH) = the quantity of heat required to change the temperature of a 1g of a substance by 1 degree Celsius or 1-degree Kelvin. Heat (q) = m (mass) X SH X change in temperature (Temp 1 - Temp 2) Units = g X J/(g X degrees C or K) X Degrees C or K Heat Transfer
- m (substance 1) X SH (substance 1) X change in temperature (substance 1) = -m (substance 2) X SH (substance 2) X change in temperature (substance 2)
- Pay attention to the negative sign on the right side of the equation. - If the negative sign is present at the end, this means that heat is released, not absorbed.
Chapter 2 We also discuss several other topics like What are the two features of anarchy?
2.1 – Dalton’s Atomic Theory
- Antoine Lavoisier’s – Law of Conservation of Mass – No measurable change in mass occurs during chemical reaction - Law of Definite Proportions – samples of the same compound always contain the same proportions by mass of the component elements. - Dalton’s Atomic Theory
1) All matter is composed of small indivisible particles called atoms. 2) All atoms of a given element are identical in mass and chemical properties, but different elements have different masses and different chemical properties.
3) Atoms are not created or destroyed in chemical reactions.
4) atoms combine in simple whole number ratios to form compounds. - A chemical reaction is a rearrangement of atoms into a new combination, resulting in one or more new chemical substances.
- Qualifications to Dalton’s Theory – The 1st statement is not strictly true, atoms are composed of smaller particles, subatomic particles, and the 2nd statement leaves out that atoms of the same element can vary in mass.
2.2 – Structure of the Atom
- Subatomic Particle – Proton, Neutron, Electron
- Electron – Negative Charge of -1.6022 X 10 ^-19 coulombs
- Proton – Positive Charge of +1.6022 X 10 ^-19 coulombs
- Neutron – Uncharged – accounts for extra mass in the nucleus - To be electrically neutral, atoms must have equal numbers of protons and electrons.
- The charge of an electron is expressed as a 1- superscript
- The charge of a proton is expressed as a 1+ superscript
- Hans Geiger and Ernest Rutherford discovered the nucleus through a gold foil experiment.
- The nucleus contains most of the mass of the atoms and electrons exist outside the nucleus in an electron “cloud”.
- Atomic Number – the number of protons in an atoms nucleus that determine the identity of that element. (Z)
- The atomic number is just above the element symbol on the periodic table. - Not all atoms of the same elements contain the same number of neutrons - Isotope - an atom of an element that has a specific number of neutrons.
- As long as the number of protons does not change the atom is still the same element no matter how many neutrons it will just be an isotope.
- Isotopes have essentially identical Chemical Properties but physical properties (melting and boiling point) may differ slightly.
- The mass number (A) equals the number of protons Z and the number of neutrons N.
- This is one way to distinguish isotopes
- The number of neutrons can be determined from the known mass number and the known atomic number.
Isotope Symbol Composition
- Mass number = protons and neutrons
- Atomic number = protons
- Subscript = proton number Z
- Superscript = mass number A
- Because each element only has one atomic number sometimes is left out of the symbol.
2.3 - Ions
- Ion - when an atom contains more or less electrons than protons and has a charge.
Cation = a positively charged ion - contains less electrons than protons Anion = a negatively charged ion that contains more electrons than protons 2.4 Atomic Mass
- The AMU - atomic mass unit - scale uses carbon-12 as the standard to express other masses of atoms
- Carbon-12 has 12 amu so one amu = 1/12 the mass of one carbon 12 atom = 1.6606X10^-24 g
- The average mass of the individual isotopes is the Relative Atomic Mass 2.5 – The Periodic Table
- On the periodic table, elements are in order of their atomic number form smallest to largest
- columns and rows emphasize periodic properties
- Horizontal row – a period – elements in the same period tent to have properties that vary in a regular fashion – periods are labeled 1 through 7
- The stair step line separates metals on the left from the nonmetals on the right
- A metalloid or semimetal is an element that has physical properties resembling a metal but chemical reactivity more like a nonmetal – metalloids are along the stair step line.
- Any element labeled with an A is a Main group element
- Any element labeled with a B is a transition metal
- The lanthanide and actinide series are the two lines on the bottom these elements are the inner transition metals
- Alkali Metals = Group 1A (reactive)
- Alkaline Earth Metals = Group 2A (Less reactive)
- Halogens = Group 7A (diatomic molecules)
- Noble Gasses = Group 8A (single, inert atoms) - Noble gasses are inert, they do not react chemically
- Diatomic Molecule – a molecule with two atoms (Have No Fear Of Ice Cold Beer) – H, N, F, O, I, Cl, Br
- The position of an element on the periodic table helps to predict the charge on its ion
- noble gasses do not form ions- they are the most stable -their stability is associated with their number of electrons.
- Nonmetals usually gain electrons to form anions that have a noble gas electron count
- Most main group elements lose electrons to form cations that have a noble gas electron count
- Ions of the same group often form electrons of the same charge
Chapter 3
3.1 – Ionic and Molecular Compounds
- For an electric current to go through a solution, ions must be present - Electrolyte – A substance that releases ions when it gets dissolved in water - Nonelectrolyte – A substance that does not release ions when dissolved in water
Dissociation/Ionization – the process by which a compound dissolves in water to produce ions.
- Strong electrolyte – dissociates easily and conducts electricity well. - Weak electrolyte – dissociates only partially and doesn’t conduct electricity well.
- Nonelectrolyte - does not dissociate into ions at all and does not conduct electricity.
Ionic Compound – Consists of oppositely charges cations and anions in proportions what are electrically neutral. Metal with a nonmetal usually. Molecular Compound – atoms of two or more nonmetals. – atoms do not dissociate
- Much lower melting and boiling points than ionic compounds.
Binary compound – a compound containing atoms/ions of only two elements. Polar molecules – molecular compounds with very slight electrical charges – weak – covalent bonds
- Acids do ionize in water even though they are molecular compounds – this is an exception.
- Acid’s dissociation in water is called ionization.
3.2 – Monatomic and Polyatomic Ions
- Monatomic Ion = an ion of a single atom
- The charges of ions for elements in the middle, especially transition metals, cannot be predicted.
Nomenclature – they system of naming
- Monatomic Anions – The first part of the element name (the root) and the suffix -ide – ex) Sulfide ion = S^2-
- Monatomic Cations – are not given a suffix – they are just the name of the element and the word ion ex) Sodium ion = Na^+ - Polyatomic Ions – an atom containing two or more atoms of usually more than one element.
- The most common polyatomic ions have oxygen attached to them – these are called Oxyanions – typically a combination of oxygen with a nonmetal (can be a metal sometimes)
- Nearly all polyatomic ions are negatively charged – Exception = NH^4+
- Rules for naming
- Greatest # of oxygen atoms – Prefix per + root name + suffix ate
- 2nd Greatest # of Oxygen atoms – Root name + suffix ate
- 2nd to Least # of Oxygen atoms – Root name + suffix ite
- Least # of Oxygen atoms – Prefix hypo + root name + suffix ite - If there are only 2 oxyanions only use the suffixes ate and ite, ate for the greater number of oxygen atoms and ite for the lesser number. 3.3 – Formulas for Ionic Compounds
- Formula Unit – the smallest repeating unit of an ionic formula – has a net charge of zero
- Chemical names start with the name of the element that is farther to the left or farther down on the periodic table.
- The name of the metal is written first.
- The formula unit does not give the exact count of ions, it gives the smallest ratio
- Molecular formulas give the exact count of ions in the molecule. - Formulas for Ions containing polyatomic ions – sum of charges must be zero - Cations appear first in both the name and the formula.
- use parentheses around a compound that appears more than once to balance a charge.
- Writing formulas from Ionic names
1st determine if a polyatomic ion is present
2nd determine the charge on the ions that make up the compound – if the ion is monatomic, look at the periodic table, if the ion is polyatomic, we must recall its charge.
3rd write the correct formula
Ex) Calcium ion + Nitride Ion = Ca 2+ and N 3- = Ca3N2
3.4 - Naming Ionic Compounds
- Binary Ionic Compounds – Cation then anion then -ide ending. – Prefixes are not used.
- Naming Compounds containing Polyatomic Ions – Cation followed by the name of the polyatomic ion.
- Many metals, especially transition metals, can exhibit multiple charges. - Stock System – using roman numerals
- In parentheses after the metal will be a roman numeral to indicate charge
- Write the name of the metal, followed by the roman numeral, then write the root of the nonmetal name with the -ide ending. - Writing formulas from names – Ex) iron(II) sulfide – iron has a charge of plus three since it is the metal cation and sulfur has a charge of 2- from the periodic table, so the formula is Fe2S3. - Older Method of Naming – the name of the metal is changes by adding the suffix -ous or -ic to the root of its Latin name. - ous is for the lower of the two charges
- ic is foe the higher of the two charges
- This method only applies to metals that can exhibit 2 charges only. - Hydrates – ionic compounds that have stoichiometric amounts of water attached to them and included in their formula units.
- Hydrates are names with prefixes (mono/di/tri etc.)
- Ex) MgSO4 7H2O = Magnesium sulfate heptahydrate
3.5 – Naming and Writing formulas for Molecular Compounds - Some nonmetals combine to form more than one compound 0 we must identify the correct ratio of atoms in the molecule. - Naming – state the name of the element that is farther to the left (or if two elements are in the same group use the one that is farther down) on the periodic table.
- Add the suffix -ide to the end of the root name of the 2nd
element.
- Use Greek Prefixes to indicate the number of atoms in the
compound.
- The prefix mono is usually not used except in the cases
of carbon monoxide nitrogen monoxide etc. - This is now the molecular formula that tells the actual number of atoms present in a single molecule of a molecular compound.
- Some binary molecular compounds are known by their trivial names, or systematic names Ex) H2O = Water
3.6 – Acids and Bases
- Acid = a substance that when dissolved in water provides hydrogen ions (H+). This is called ionization when a compound that is not an ionic compound provides ions when dissolved in water.
- Acids are molecular compounds but behave differently.
- The H+ ion does not exist in solution by itself it is usually surrounded by water molecules that form a hydronium ion H3O+ - Organic acids are compounds that contain the combination of atoms C, O2, and H – these are called Carboxylic acids. Ex) CH3CO2H - Not all compounds containing hydrogen are acids in water – only when hydrogen combines with an element on the far right of the periodic table (excluding noble gasses) the compound is an acid. - Writing Formulas for Acids – place the hydrogen first and write (aq) at the end to indicate that it is an acid. Ex) HCl (aq)
- Hydrogens with a polyatomic ion can also be an acid. Ex) Nitric Acid HNO3 - Binary Acids in Solution – named with the prefix hydro- followed by the stem of the nonmetal name with the suffix -ic and the word acid at the end.
- Naming acids with a polyatomic ion
– The prefix hydro- is not used – remove the -ate ending from the polyatomic ion and replace it with -ic. - If the polyatomic ion has less oxygen atoms, replace the -ite ending with -ous.
-Base = a substance that reacts with an acid in an aqueous solution to form H2O. - Most common bases contain a Hydroxide ion (OH-) or can produce OH- ions when in solution.
- Some Common Bases – NaOH, KOH, Mg(OH)2, NH3 ammonium. - Strong Acids and bases ionize/dissociate completely and are strong electrolytes. - Weak Acids and bases are wear electrolytes ex) Acetic Acid.
3.7 – Predicting Properties and Naming Compounds
- By deducing the elements in a compound from its name or formula, we can predict many of its properties.
- Ex) MgCl2 – it has a metal and a nonmetal so the compound is ionic which must mean that it may be a brittle solid with a high melting and boiling point and we can name it by ionic rules.
- Diprotic Acids = 2 hydrogen protons – Triprotic acids = 3 hydrogen protons
- When writing a chemical formula, write the symbols in the order in which the elements appear going from left to right on the periodic table. - If two elements are in the same column, write the name of the element that is lower 1st.
- Hydrogen Exception – write H AFTER all elements EXCEPT those in groups 6A and 7A.
Chapter 4
4.1 – Percent composition – an expression of the proportion of the total mass contributed by each element.
- Constant no matter the sample size – follows the law of definite proportions. - % element = (mass (g) element/ mass (g) sample) X 100%
- The percent masses of each element in the compound/ sample should all add up to 100%.
- We can also find Mass from % composition. – Use 100g as a sample base - Mass of sample (g) X (% element changed into (g)/ 100g sample) = Mass of element in the given sample.
4.2 – Mole Quantities
- A Mole = 6.022 X 10^23 atoms/ions/molecules/formula units
- 6.022X 10^23 = Avogadro’s Number – the same as the number of atoms in exactly 12g of carbon-12
- 1 Mole can contain different volumes and different masses of different materials, but it is always the same amount of formula units
(atoms/ions/molecules/formula units).
- To calculate the number of formula units, multiply the number of moles by the conversion factor that cancels out moles using Avogadro’s number. - 2 mole Cu X (6.022X10^23 formula units/ 1 mole Cu) =
1.204X10^24 formula units Cu
- To calculate the number of atoms/ ions in 1 mole of an element, add a step to the previous equation looking at the chemical formula to determine how many atoms or ions are in 1 molecule or formula unit.
- 1 mole O2 X (6.022X10^23 molecules O2/ 1 mole O2) X ( 2 O atoms/ 1 molecule O2) = 1.204 X 10^23 O atoms
- Molar Mass = (MM) The mass of 1 mole of a substance – Use the periodic table to determine the molar mass of any element or compound. – If a compound, the molar mass is equal to the sum of all relative atomic massed of its component elements.
- Moles from Mass - Mass (g) of the substance X (1 mole Substance/ MM (g) substance) = Moles Substance
- Mass from Moles – Moles substance X (MM (g) substance/ 1 mole substance) = Mass (g) substance
- Moles to Atoms – Moles element X (6.022X10^23 atoms element/1 mole element) = Atoms element
- Molecules from Mass – 150g sample X (1 mole sample/ MM (g) sample) X (6.022X10^23 molecules sample/ 1 mole Sample) = Molecules sample 4.3 – Determining Empirical and Molecular Formulas
- Empirical Formula (EF = my abbreviation) – expresses the simplest ratios of atoms in a compound – written with the smallest whole number subscripts. - To find the EF, determine the smallest subscript and divide the other subscripts by its value, or another least common factor.
- If the subscripts are not evenly divisible by a number other than 1, then the EF and the molecular formula are not the same.
- The molecular formula is either the same as or a multiple of the EF. – Molecular formulas contain more information than EFs.
- Determining Empirical formulas from data on the chemical composition of a compound.
- If given masses of elements in a compound, convert them to moles using MM.
- We need to convert the number of moles into whole numbers of atoms, so take the smallest number of moles of an element
and divide the moles of the other elements by this number.
- This will give you the number of moles of each element, which can be translated to subscript numbers in a chemical formula.
- Empirical Formulas from Percent Composition containing 2 elements and more than 2 elements.
- Convert the percent composition of the elements in the compound to g of that compound using 100g hypothetical sample.
- Convert the mass of each element to moles using MM.
- Divide each moles of element by the smallest of the mole quantities. - Now you have whole number moles that you can turn into subscripts for the EF
- For more than 2 elements, just add in the step to convert the extra elements.
- Empirical Formulas with fractional mole ratios.
- Decimal places may not always be close to whole numbers, thus rounding is not appropriate. Ratios may have fractional values like 1.25 or 1.5. In this case, multiply each ratio by a small whole number to make all of the subscripts whole numbers.
- Molecular Formulas from Empirical Formulas.
- We can calculate the mass of 1 mole of formula units using the EF. - If the experimental MM is the same as the calculated MM, the molecular formula is the same as the EF.
- If the experimental MM is greater than the calculated MM of the formula, the molecular is some multiple of the empirical formula.
- Experimental MM/ EF MM (calculated) = The multiple that the molecular formula is greater by.
- Determining Percent Composition from Chemical Formula
- If we know the chemical formula of a compounds, we can use the relationship between moles and mass to determine its % composition without having to determine mass.
- To simplify converting a chemical formula into % composition, assume a sample size of 1 mole.
- The mass of an element in 1 mole of the compound is equal to the number of moles of the element multiplied by the MM of the element.
- The % composition of the element then equals the Mass of the element divided by the MM of the whole compound, multiplied by 100% to get % composition.
4.4 – Chemical Composition of Solutions
- Chemical reactions between solids are normally slow, so to speed up reactions, we usually carry out such reactions by first dissolving the compound in a liquid to form a solution.
- Solute = The substance being dissolved (present in a lesser amount) - Solvent = The substance doing the dissolving (present in a greater amount) - Concentration – The relative amounts of solute and solvent in the solution. - When comparing solutions, we can describe them as dilute or concentrated. - A dilute solution contains a relatively small amount of solute.
- A concentrated solution contains a relatively large amount of solute. - Indications of concentration that are not very accurate =
Taste/color/density/viscosity by observation.
- Percent by Mass – the % by mass of a solution equals the mass of the solute divided by the mass of a solution multiplied by 100%.
- % mass = (Mass of solute/Mass of solution) X 100%
- The mass of the solution is the sum of the masses of solute and solvent.
- This method does not depend on temperature. Volume may change with temperature, but the mass does not. - % mass is also unaffected by the presence of solute, unlike volume.
- Molarity (M) = The concentration of a solution can be expressed by molarity, the number of moles of solute dissolved in 1 L of solution.
- Molarity = Moles of solute/Liters of Solution
- Molarity from Mass
- Find the moles of solute using MM.
- Convert volume to liters, if not already liters.
- Divide the moles of solute by the volume of the solution in liters to get Molarity.
- Moles from Volume and Molarity
- To get moles form volume, multiply by the molarity conversion factor that cancels out units of liters and gives units of moles.
- Determine the moles of ions/atoms by looking at the chemical formula and determine how many moles of that ion/atom are in the formula unit.
- To get moles of the ion/atom, use the conversion factor that cancels the appropriate unit. You are not left with moles of the specific ion/atom in the formula unit/molecule.
- Mass from Volume and Molarity
- If we know the volume and molarity of a solution, we can calculate the mass of solute in that volume of solution
- To determine the mass of the solute, 1st determine the moles of solute by multiplying the molarity by the volume of solution in L to cancel out L and be left with moles.
- Convert moles to mass using MM.
- Volume from Molarity and Mass
- We can calculate the volume of a solution required to make a solution of a specific concentration from a given amount of solute.
- Given molarity and mass, convert mass to moles using MM. - Convert moles to volume of solution in L by multiplying the moles of solute by the molarity conversion factor that cancels out moles and be left with L.
- Dilution – to lower the concentration of a solution, we use the process of dilution, adding more solvent to a solution. The relative numbers of solute and solvent particles increase and the number of solvent particles increases the volume, but the number of solute particles stays the same and now they are spread out through a greater volume, so their concentration is less.
- If we dilute a solution of a known molarity and, we can calculate the molarity of the diluted solution.
- Moles (concentrated) = Molarity (concentrated) X Volume (concentrated)
- Moles (concentrated) = Moles (diluted)
- Moles (diluted) = Molarity (diluted) X Volume (diluted)
Therefore – M(dil) X V(dil) = M(conc) X V(conc)
Rearrange this equation to solve for the Molarity of the diluted solution - M(dil) = (Mconc X Vconc)/V(dil)
- This formula can be rearranged to solve for any one of these four variables.