chapter 3

• MgO, P2O2, CoF2, Al(NO3)3 are chemicals.
• All chemical reactions are described by a chemical equation which tells what all the reactants and products of the reaction are, along with their phase.
• A balanced chemical equation is a chemical equation which has the same number of atoms of each element on the reactant and product side by using coefficients to describes how many reactants and how many products are involved in the reaction.
• Combustion is the burning of anything in the presence of Oxygen.
• The reactants in combustion are always a fuel and Oxygen, and the products are always CO2, H2O and nothing else.
• The equation for combustion is: CxHyOz + O2 → CO2 + H2O.
• Combustion can also be represented as a redox reaction:
• 2 H2(g) + O2(g) → 2 H2O(g).
• The coefficients in a reaction are the number of each reactant and product involved in one instance of the reaction.
• When listing the reactants and products involved, you must specify the phase of matter of each chemical if you know it.
• There are four phases that we use: Solid (represented as X(s) – a dense crystalline substance of definite shape), Liquid (represented as X(l) – a substance of definite volume, but fluid shape), Gas (represented as X(g) – a substance of indefinite volume that expands to fill the area), Aqueous (represented as X(aq) – a compound that is dissolved in water).
• C8H18(l) + O2(g) → CO2(g) + H2O(g) is a chemical equation.
• Balancing chemical equations involves finding the number of atoms on each side (reactants vs products), starting with an atom that is only present in one species, and having whole numbers as coefficients.
• In the chemical equation CaCl2(aq) + Na2CO3(aq) → CaCO3(s) + 2 NaCl(aq), CaCl2(aq) is a reactant and Na2CO3(aq) is a product.
• When metals and nonmetals combine, they create balanced ionic compounds such as Rb + O2 → RbO2.
• Many other reactions create simple gases like CO2, NH3 and H2O.
• N2 + H2 → NH3 is an example of a reaction that creates a simple gas.
• When molecules fall apart, they often form their elements in their most stable state.
• For H, N, O, F, Cl, Br and I, this is diatomic meaning that two atoms of the same atoms are bonded together.
• One special case to keep in mind: Carbonates (CO32-) decompose to form an oxide and CO22.
• BaCO3 → BaO2 + CO2 is an example of a decomposition reaction.
• The mole simplifies the conversation about atoms, which are very small and there are a lot of them.
• Avogadro’s Number is 6.022*10^23 atoms.
• The formula mass for aluminum sulfate is 342.14 g/mol, calculated as 2(26.98 g/mol) + 3(32.06 g/mol) + 12(16.00 g/mol).
• The molecular formula for aluminum sulfate can be determined from the empirical formula by finding the total molar mass.
• 1 mole of atoms means 6.022*10^23 atoms.
• 1 mole of electrons means 6.022*10^23 electrons.
• 1 mole of footballs means 6.022*10^23 footballs.
• When 5 moles of N2(g) react with 9 moles of H2(g) by the reaction below, how much NH3(g) is created?
• N2(g) + 3 H2(g)  2 NH3(aq)
• If all 9 moles of H2(g) react, how much NH3(g) would be formed?
• How much total NH3(g) is formed?
• Each He atom weighs 6.65*10^-24 g.
• 1 g/mol = 1amu.
• On the Periodic Table, sulfur has a molar mass of 32.066 amu = 32.066 g/mol.
• The mass (in grams) of one sulfur atom is 5.3248*10^-23 g.
• Formula Mass is the average atomic mass of one fundamental unit and is the sum of the mass of all of the atoms in one molecule (for covalent substances) or one formula unit (for ionic substances).
• A sample is 34.28 % carbon, 4.73 % hydrogen and 60.95 % oxygen by mass.
• The empirical formula of the compound is determined to be C3H5O4.
• If the compound has a molar mass of 420.32 g/mol, the molecular formula is determined by multiplying each subscript in the empirical formula by this value, resulting in the molecular formula C12H20O16.