February 16, Stoichiometry.notebook. Feb 4 8:11 PM. Feb 4 8:09 PM. Feb 4 8:13 PM. Feb 4 8:28 PM. Feb 4 8:13 PM.

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1 Stoichiometry You already know how to predict what products are produced. The goal of stoich is to predict how much products are produced. 4 Major Types of Stoichiometry Problems 1. Mole Mole 2. Mass Mass 3. Volume Volume 4. Mix Stoichiometry: the mathematical relationship between the reactants & products in a chemical rxn. Mole Ratio a proportion given by the coefficients in a BCE telling the relative number of moles of each substance. 5 Steps in Solving Stoichiometry Problems 1. Write the BCE (Balanced Chemical Equation) 2. Write down the given with units & labels 3. Set up a conversion 4. Using your new and improved road map (Y chart) to determine the bes route to get to your unknown. 5. Cross out and solve. Be sure to use the number of sig fig s from the given to report your answer and use units & label. Feb 4 8:09 PM Feb 4 8:11 PM Mole Mole Stoichiometry Problems Ex. 1: Nitrogen gas and hydrogen gas are combined to form ammonia. If I start with 250 moles of nitrogen, how many moles of ammonia will be produced? Ex. 2: When KCl 3 decomposes, how many moles of oxygen are produced if you start with 750 moles of the reactant. 5 Steps in Solving Stoichiometry Problems 1. Write the BCE (Balanced Chemical Equation) 2. Write down the given with units & labels 3. Set up a conversion 4. Using your new and improved road map (Y chart) to determine the bes route to get to your unknown. 5. Cross out and solve. Be sure to use the number of sig fig s from the given to report your answer and use units & label. Feb 4 8:28 PM Mass Mass Stoichiometry Problems Ex. 1: ow many grams of 2 would be made from 3.0g of 2? Volume Volume Stoichiometry Problems Ex. 1: If 5.0 L of methane (C 4 ) burns in the presence of oxygen, how many liters of C 2 will be produced? Ex. 2: 3Fe(s) + 42(g) Fe34(s) + 42(g) If 36.0g of 2 react completely, what is the mass of Fe34(s)? Ex. 2: In the space shuttle, exhaled carbon dioxide gas is removed from the air by passing it through canisters of lithium hydroxide; this reaction produces solid lithium carbonate & gaseous water. ow many liters of water are produced from 3.4 liters of exhaled carbon dioxide? Ex. 3: Nitrogen combines with oxygen in the atmosphere during lightning flashes to form nitrogen monoxide. If 42.1g of N are produced, how many grams of 2 are needed? 1

2 Energy in Chemical Rxn s Molar eat energy per mol of reactant release in a chemical reaction. the B. C. E. to determine molar heat. Use kJ 572kJ/2 mol 2 or 572kJ/1 mol 2 EX. n average, each person in the U.S. consumes 110 g of sugar daily. If all of this sugar is assumed to be glucose, how much heat energy form glucose is transferred to one person through respiration each day? C C 2(g) kJ Feb 4 8:14 PM Feb 15 8:15 AM Limiting Reactants Limiting Reactants limits the amount of products that can be produced Excess Reactant reactant that is left over after the reaction stops 5 Steps to Limiting Reactant Problems 1. Write BCE. 2. Determine moles of each reactant. 3. Determine the amount that you NEED using the mole ratio. 4. Determine Limiting Reactant. Compare what you have & need. 5. Use the limiting reactant to answer the question. Feb 4 8:33 PM Feb 11 11:17 AM Feb 11 11:25 AM Feb 12 8:12 AM 2

3 Thermodynamics (heat moving) Which had a greater average kinetic energy? Which has a greater total energy at the same temperature? Temperature T, is the measure of the average kinetic energy of individual molecules. Faster molecules means higher temperature The amount of substance doesn t matter Measured in Celsius or Kelvin Lower Limit = Absolute Zero (K.E. is 0) Upper Limit = There isn't one. Feb 11 11:44 AM Feb 11 11:45 AM Thermal Energy, the sum of all the energy of all the molecules in a object The amount of substance does matter Measured in Joules or calories 1 J = kg. m 2 /s J = 1 cal When I take pizza out of an oven, why can I burn myself on the sauce but not on the crust? They have different specific heats. Specific heat how much heat it takes to raise the temp of one kilogram of a substance one degree Kelvin or Celsius. Which has a higher specific heat, water or sand? Q = mcδt **Units must agree Feb 11 11:46 AM Mar 30 9:34 AM What is the specific heat of a metal with a mass of 38 kg if it absorbs 1.0 x 10 6 J while being heated for 26 o C to 180 o C? What metal is it? What metal is it? Brass J/g.o C Copper J/g.o C Gold J/g.o C Zinc 0.388J /g.o C Mar 30 9:36 AM Feb 19 2:13 PM 3

4 Conservation of Energy Energy can neither be created nor destroyed (What goes into the system must come out.) eat gained = eat lost Q G = Q L mcδt = mcδt Ex. 200g of 10 o water is contained in a calorimeter. If 95.0g of 90 o water is added, what is the equilibrium temperature of the system? Feb 19 2:28 PM Feb 20 7:15 AM *** When a substance changes states, adding energy (heat) doesn t increase temperature. eating Curve for Water. eat of Vaporization vap = cond, Energy needed to boil or condense eat of Fusion fus = melt, Energy needed to melt or freeze Feb 20 7:12 AM Feb 20 7:27 AM Feb 15 8:21 AM 4

5 Attachments MLE RELATINSIPS WITIN A CEMICAL REACTIN.doc Stoichiometry.doc mole rockets.doc eat Energy in Chemical Changes.doc