Stoichiometry PDF

Stoichiometric coefficients indicate the STOICHIOMETRY relative amounts of reactants and products in the reaction. Mole - a mole...

Stoichiometric coefficients indicate the STOICHIOMETRY relative amounts of reactants and products in the reaction. Mole - a mole represents a quantity of a number, Compound states are indicated by symbols: the same way a “dozen” does. (l) for liquid, (s) for solid, (g) for gas, and (aq) 1 dozen = 12 for an aqueous solution. 1 mole = 6.022 𝑥 1023 = Avogadro’s Number Types of Chemical Reactions Molecular and Empirical Formula 1. Combination Reaction - two or more Molecular Formula - how many atoms of substances combine to form one product. each element are in a compound General Formula: A + B → AB Patterns for Combination Reactions Empirical Formula - the simplest or most Metal + Nonmetal → Binary Compound reduced ratio of atoms in a compound Nonmetal + Oxygen → Nonmetal Oxide Metal + Water → Metal Hydroxide (base) Nonmetal oxide + Water → Oxyacid (acid) Metal oxide + Nonmetal oxide → salt 2. Decomposition Reaction - a compound is decomposed to form two or more substances General Formula: AB △→ A + B Patterns for Decomposition Reactions Butene Hydrates △→ salt + water Molecular = C4H8 IA Bicarbonates △→ Carbonates + H2O (g) 4 Carbon atoms + CO2 8 Hydrogen atoms IIA Bicarbonates △→ Metal oxide + H2O (g) + CO2 Empirical = CH2 Carbonates △→ Metal oxide + CO2 4 C= 1C Chlorates △→ Chlorine + Oxygen 8H 2H Metal oxide △→ Metal + Oxygen Water △→ Hydrogen + Oxygen If the ratio of atoms in the molecular formula can’t 3. Displacement Reaction - more active metal be simplified any further, the empirical formula can displace a less active metal, while a less becomes the same as the molecular formula. active one can’t displace the more active. General form: AY + B → BY + A; where A and B Percentage Composition - the percent by mass of are metals based on its activity series each element in a compound 4. Metathesis (Double Displacement Reaction) 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑙𝑒𝑚𝑒𝑛𝑡 - the positive ions exchange partners with the %𝑚𝑎𝑠𝑠 = 𝑥 100 negative ions to form two new compounds. 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑐𝑜𝑚𝑝𝑜𝑢𝑛𝑑 General Form: AY + BX → BY + AX Example: H2O All neutralization reactions involving acids and bases are actually metathesis reactions. Mass of compound = 18.02 Any carbonate, either in the solid state or Mass of H2 = 2.02 aqueous solution, reacts with acid to form Mass of O2 = 16 water, carbon dioxide gas, and salt. 2.02 5. Neutralization Reaction % Hydrogen = 18.02 𝑥100 = 11.2% Acid + Base → Salt + Water 16 % Oxygen= 18.02 𝑥100 = 88.8% Metal oxide + acid → Salt + Water Nonmetal oxide + Base → salt + water Chemical Reactions - involve the interaction of Ammonia + Acid → Ammonium salt chemicals to form new substances Chemical Stoichiometry represented by a chemical equation The left side of the equation represents the Stoichiometry - used to describe the quantitative reactants; the right side represents the relationships between the reactants and products in products. a chemical reaction.  Present in small Does not change its amount phase in the formation Dissolved substance of solution Dissolving medium Limiting Reactant Solubility factors The reactant that is completely consumed during a chemical reaction. 1. Nature of Solute and Solvent It determines the maximum amount of A solute can only be dissolved in a solvent when product that can be formed. they are alike. A general rule is “like dissolves like” Once the limiting reagent is used up, the reaction stops, even if other reactants are still 2. Temperature available. For solid and liquid: solute increases when temperature is increased. Excess Reactant The reactant(s) that remain after the reaction For a gaseous: solute to a liquid solvent decreases has completed. as temperature increases. They are not fully consumed because there are more of them than needed to react with 3. Pressure the limiting reagent. The effect of pressure is only applicable for the Excess reactants are often left over after the solubility of gasses in liquids. The higher the reaction ends. pressure of a gas, the more soluble it is. How to Determine the Limiting and Excess Types of solution Reactant: 1. Unsaturated Solution - solvent can still dissolve the solute 1. Write the Balanced Equation: Ensure the chemical equation for the reaction is 2. Saturated Solution - if a solvent can’t no longer balanced. dissolve a given solute at a given temperature 2. Convert Quantities to Moles: Convert the masses or volumes of the reactants to 3. Supersaturated Solution - if the solvent can’t moles. dissolve the solute and need to be heated for it to be 3. Calculate the Mole Ratio: Use the dissolved balanced equation to find the mole ratio between the reactants. Solubility rules in Water at 25 deg C 4. Compare the Mole Ratio to Determine the Limiting Reactant: Insoluble Soluble Compounds ○ Calculate how much of each Compounds reactant is required based on the All nitrates, All carbonates, mole ratio. bicarbonates, phosphates, ○ Identify which reactant runs out first chlorates chromates, by comparing the actual amounts and compounds and sulfides except available to the required amounts. containing alkali metal that of alkali metal This reactant is the limiting reactant. ions and ammonium ions and ammonium 5. Calculate the Amount of Product ion. ion. Formed: Use the amount of the limiting All halides except that All hydroxides except reactant to determine the amount of product of Ag+, Hg2 2+ and Pb2+ that of alkali metal ions formed. All sulfates except that and Ba++ 6. Determine the Excess Reactant: Subtract of Ag+, Ca++, Sr++, Ba++ the amount of the excess reactant that and Pb++ actually reacts from the total amount available to find how much of it is left over. Concentrations of Solutions SOLUTION Weight/Weight Percent A homogeneous mixture consisting of solute and solvent. 𝑤 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 % = × 100 Solute Solvent 𝑤 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 Weight/Volume Percent  𝑤 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 (𝑔) 𝐾𝑝 % = × 100 𝐾𝑐 = (𝑅𝑇)∆𝑛 𝑉 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 (𝐿) Parts per Million (ppm) where ∆n = (total moles of gas on the product side) - (total moles of gas on the reactant 𝜇𝑔 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝑚𝑔 𝑠𝑜𝑙𝑢𝑡𝑒 side) 𝑝𝑝𝑚 = = 𝑔 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝐿 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 Characteristics of Equilibrium Constant Parts per Billion (ppm) 1. Changes in concentration, pressure, 𝑛𝑔 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 𝜇𝑔 𝑠𝑜𝑙𝑢𝑡𝑒 temperature, or the presence of inert gasses 𝑝𝑝𝑏 = = 𝑔 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 𝐿 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 can shift the equilibrium but do not change Molarity the equilibrium constant itself. 2. The equilibrium constant is related to the 𝑚𝑜𝑙 𝑠𝑜𝑙𝑢𝑡𝑒 standard free energy change (△G°) by the 𝑀𝑜𝑙𝑎𝑟𝑖𝑡𝑦 (𝑀) = 𝐿 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 equation: △G° = -RT ln Kequ. 3. The equilibrium constant for the reverse Molality reaction is the reciprocal of the original 1 𝑚𝑜𝑙 𝑠𝑜𝑙𝑢𝑡𝑒 constant, i.e., Krev = 𝐾. 𝑀𝑜𝑙𝑎𝑙𝑖𝑡𝑦 (𝑚) = 𝑒𝑞𝑢 𝑘𝑔 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 4. If the stoichiometry of the reaction changes, Normality the equilibrium constant is raised to the power corresponding to the change. 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒 5. For a reaction A + B ⇌ C + D with constant 𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑡𝑦 (𝑁) = = 𝑛𝑀 𝐿 𝑠𝑜𝑙𝑢𝑡𝑖𝑜𝑛 K, if the equation is multiplied by 4, the equilibrium constant becomes K4. Equivalents per Mole 6. In stepwise reactions leading to final 𝑒𝑞 products, the net equilibrium constant is the 𝑛( ) = 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝐻 + , 𝑂𝐻 − , 𝑜𝑟 𝑒 − product of each individual step’s equilibrium 𝑚𝑜𝑙 constant, K = K₁ × K₂ × K₃. 7. For reactions with a common product, the INTRODUCTION TO CHEMICAL EQUILIBRIUM equilibrium constant remains unchanged, but higher concentrations of the common Chemical Equilibrium → Chemical reactions tend product can decrease the concentration of to move towards a dynamic equilibrium in which both other products. reactants and products are present but have no further tendency to undergo net change. FACTORS AFFECTING CHEMICAL EQUILIBRIUM AND ITS RESPONSE Equilibrium Law → Describes the relationship between the concentrations of reactants and Le Chatelier’s Principle → If a system at products in a chemical reaction at equilibrium. It is equilibrium is subjected to a change in concentration expressed by the equilibrium constant (K) (C), pressure (P), or temperature (T), the system will adjust itself to counteract the disturbance and Equilibrium Constant (KC) → Ratio of the restore a new equilibrium. concentration of products to the concentration of the reactants, each raised to their respective Summary of Le Chatelier’s Principle: stoichiometric coefficients. Value of Change in Additionally: Factor Change Equilibrium Reason Equilibrium to System Constant Position (Kc) Kc represents the equilibrium constant Extra measured in moles per liter Shifts away concentration Increase from No change [𝐶]𝑐 [𝐷]𝑑 needs to be (concentration).𝐾𝑐 = [𝐴]𝑎[𝐵]𝑏 substance used up C Need to produce more Kp represents the equilibrium constant Shifts of substance Decrease toward No change calculated using the partial pressures of to make up for substance what was gasses. removed [𝑝𝐶]𝑐 [𝑝𝐷]𝑑 For gas: 𝐾𝑝 = Shift Pressure [𝑝𝐴]𝑎 [𝑝𝐵]𝑏 P Increase towards side increase = No change with fewer Volume moles of gas Relationship Between Kc and Kp: decrease  0 0 Shift For gas: 2. Beta Decay → 𝛽−1 or 𝑒−1 Pressure Decrease towards side decrease = No change → emission of beta particles with more moles of gas Volume → it has a negative charge, intermediate increase penetrating and ionizing power. Shifts away Extra heat / Increase from heat / energy must Yes 3. Gamma Emission → 𝛾00 energy be used up → it has a no charge, very high More heat / penetrating power and very low ionizing T Shifts energy needs towards to be power. Decrease Yes 0 0 heat / produced to 4. Positron Emission → 𝛽+1 or 𝑒+1 energy make up for the loss 5. Electron Capture → 𝛾00 and 𝑒−10 Rates of both forward and Catalyst reverse and Inert - No Shift reactions are No change Gasses increased by the same amount KINETICS OF DECAY Half-life (t1/2) → also called as the decay time → uses the concept of first-order reaction to NUCLEAR CHEMISTRY AND NUCLEAR determine the time wherein the sample has lost half ENERGY of its content. First-order Half-life Activity NUCLEAR BINDING ENERGY AND NUCLEAR Reaction STABILITY 𝑁 𝑙𝑛 2 = 𝑘𝑡1 𝑎 = 𝑘𝑁 𝑙𝑛 = −𝑘𝑡 2 𝑁0 Nuclear Binding Energy → the energy required to → N is the remaining amount after time t, N0 id the separate a nucleus into neutrons and protons, which initial amount, t is the time lapsed and k is the decay are held with strong nuclear forces constant → 𝐸 = 𝛥𝑚𝑐 2 ; Dm is the mass defect (difference of the total mass of individual particles in the atom and NUCLEAR REACTORS the actual mass of the atom) and c is the speed of light Nuclear Reactors → contains and control nuclear fission (splitting apart of atoms) that release energy Radioactivity → emission of protons, neutrons, and in the form of heat electromagnetic waves from the nucleus of an unstable atom Uranium-235 → a common nuclear fuel which is capable of producing nuclear reaction and it can Radioactive Decay → process of losing energy readily undergo fission through light emission of an unstable nucleus Nuclear Stability → determines whether the atom will undergo radioactive decay Stable Unstable Even number of > 84 protons protons and neutrons Magic number of Neutron to proton protons and neutrons: ratio > 1 2, 8, 20, 28, 50 82, 126 TYPES OF RADIOACTIVE DECAY Parts of Nuclear Reactor Types of Radioactive Decay 1. Core → contains the fuel elements and 1. Alpha Decay →𝑎24 or 𝐻𝑒24 moderator; it is where the nuclear → emission of alpha particles reaction occurs → it has a positive charge, very low 2. Moderator → reduces speed of penetrating power and very high ionizing neutrons; usually light-water power. 3. Control Rods → control the rate of nuclear reaction by adsorbing excess neutrons; made up of Cadmium and Boron 4. Steam Generator → a heat exchanger that is used to produce the steam