Download Stoichiometry and Chemical Reactions and more Study Guides, Projects, Research Chemistry in PDF only on Docsity! Unit 4: Stoichiometry&Chemical Reactions Ionic & Net Ionic Equations: โ Molecular Equation: Regular chemical reaction โ Mg(NO 3 ) 2 (aq) + K 2 CO 3 (aq)โถMgCO 3 (s) + 2KNO 3 (aq) โ Ionic Equation: Disacciotes aqueous ions from ionic compound โ NEVER split covalent compounds and pure elements โ There are always and only 2 ions in each ionic compound, and each have a charge โ To determine charge: It is the ionic charge, and add up the charges for the # of molecules which will add up to charge of compound โ Mg 2+ (aq) + 2NO 3 - (aq) + 2K + (aq)+ CO 3 2- (aq)โถMgCO 3 (s) + 2K + (aq) + 2NO 3 - (aq) โ Net Ionic Equation: Ionic Equation without spectator ions โ Spectator Ions: donโt change state throughout the reaction and/or donโt covalently bond โ Essentially irrelevant to reactionโs occurrence โ Mg 2+ (aq) + 2NO 3 - (aq) + 2K + (aq) + CO 3 2- (aq)โถMgCO 3 (s) + 2K + (aq) + 2NO 3 - (aq) โ Mg 2+ (aq) + CO 3 2- (aq)โถMgCO 3 (s) Types of Reactions: โ Precipitation:Mix ionic solutions to form an insoluble ionic compound โ (aq) + (aq)โถ (s) + (aq) โ Evidence: There is now a solid when there wasnโt one before โ Evidence has to be something you can see on the macroscale โ Soluble Products have: K + , Na + , NH 4 + , NO 3 - โ Anything else does NOT dissolve โ Acid-Base: Involves a transfer of an H + ion (a proton) from one substance (acid) to another (base) โ HA + Bโถ A - + HB + โ Evidence: usually a release of heat โ Redox: Transfer of one or more electrons from one substance to another โ Assign oxidation numbers and see if they change for an element โ Oxidation Numbers: โ Pure Element: 0 โ Hydrogen: +1 โ Oxygen: -2 โ Fluorine: -1 โ Any with above^: balance the compound so ONs add up to cmpd charge โ Any other: Ionโs Charge โ *Combustion is redox! โ To look for: Pure element formed a compound with another substance โ MOLECULAR CHANGE: Bonds formed or broken (not including ionic unless precipitate solid) Particle Diagrams: โ A container for each reactant and one container for the product side โ The number of moles IS the number of particles for each substance โ 2 moles of CuCl 2 = 2 Cu 2+ particles & 4 Cl - particles โ PAY ATTENTION TO SIZE (energy levels) โ Solids: At the bottom touching likeโฏโฏโฏ โ If more than one solid in a container, label with cmpd name โ NO CHARGE โ Gases: โfloatingโ at the top and the farthest possible from one another โ Liquids: At the bottom, oriented according to polarity โ Aqueous: โ With a line at the top to indicate water โ Ions dissociated with charge (including #) โ Ion has either: Metal or NH 4 + โ Charge can be on outside โ *Covalent compounds CAN be in aq state โ Covalent Compounds: Check to see if the right number of molecules per particle are drawn โ NEVER SEPARATE, I REPEAT, NEVER! Empirical Formula: The lowest mole-to-mole ratio for a compound โ Percent Composition (ratio) of a compound: Percent of the mass of each element in a compound โ Remember: SHOW ALL WORK!! EVERY SINGLE CALCULATION 1. Pick any sample size (total mass of cmpd)โถ 100g 2. Use % composition to find the mass of each element 3. Convert all masses to moles 4. Divide all mole quantities by the smallest mole quantity a. Multiply by an LCM to achieve whole numbers 5. The EF is: X mole: x Y mole: y Z mole: z etc Molecular Formula: The actual formula of the compound โ Need Molar Mass of compound 1. Divide Molar Mass of EF by actual molar mass to determine a multiplier 2. Multiply all EF subscripts by the multiplier Combustion Reactions: C x H y (--) z + O 2 โถ CO 2 + H 2 O โ Need to know C x H y (--) z as a reactant โ The masses of each individual element produced adds up to the sample mass 1. Determine mol of C with grams of CO 2 a. ๐ ๐ถ๐2 ๐ฅ 1 ๐๐๐๐ ๐ถ๐2 ๐ฅ 1 ๐๐๐ ๐ถ 44.01๐ (๐๐๐๐๐ ๐๐๐ ๐ ๐ถ๐2) ๐ฅ 1 ๐๐๐ ๐ถ๐2 2
