Presentation on theme: "Hydrogen gas + nitrogen gas ----> ammonia gas"— Presentation transcript:
1 STOICHIOMETRY Mass relationship of reactants and products in a chemical reaction Hydrogen gas + nitrogen gas ----> ammonia gasQualitative: describes the “nature” of the reactants and productsQuantitative: describes the amounts of reactants and products
2 Steps for solving Stoichiometry problems: Write a balanced equation for the question.Understand the mole and molar ratioConvert mass of reactant to moles of reactant.Convert moles of reactant to moles of product.Convert moles of product to grams of product.Pick up the calculator and do the math!!
3 How about something a little easier to follow???? Like…………. FOOD!!!!!
4 The Stoichiometry of a sandwich….. The SMCHS famous sandwich consists of 2 slices of bread, 2 slices of deli meat, 1 slice of cheese, and 3 slices of pickle.Write an equation for the recipe…...2 slices bread + 2 slices meat + 1 slice cheese + 3 slices pickle sandwichOR…..2B + 2M + 1C + 3P B2M2CP3
5 EVALUATION: WE CAN MAKE 4 COMPLETE SANDWICHES!! How many SMCHS famous sandwiches can be produced when 8 slices of bread, 8 slices of meat, 4 slices of cheese, and 12 slices of pickles are available?Break it down…..BREAD: 8B = 4 B2M2CP3MEAT: M = 4 B2M2CP3CHEESE: 4C = 4 B2M2CP3PICKLES: 12P = 4 B2M2CP3EVALUATION: WE CAN MAKE 4 COMPLETE SANDWICHES!!
6 How many of each ingredient is needed to make 10 SMCHS famous sandwiches? BREAK IT DOWN…..BREAD: 10B2M2CP3 x (2B / B2M2CP3 )= 20BMEAT: 10B2M2CP3 x (2M / B2M2CP3 )= 20MCHEESE: 10B2M2CP3 x (1C / B2M2CP3 )= 10CPICKLES: 10B2M2CP3 x (3P / B2M2CP3 )= 30PTHUS: 10 Sandwiches require 20B, 20M, 10C, and 30P
7 But what if you ran out of pickles? Pickles would be the LIMITING REAGENT for the sandwichesIn any reaction you will likely have a limiting reagent AND an excess reagent.Too little of oneToo much of the other
8 3 H2 + 1 N2 2NH3 What do the coefficients mean? 3 molecules : 1 molecule : 2 moleculesOR 3 moles : 1 mole : 2 moles
10 allowing you to solve problems dealing with masses of substances! 1N2 + 3H2 2NH31mole of : 3mole of : 2mole ofN2 molecules H2 molecules NH3 moleculesThis is the MOLAR RATIOallowing you to solve problems dealing with masses of substances!
11 1 N2 + 3 H2 2 NH3 If 75g of hydrogen reacts, A) How many g of N2 reacts?Use the molar ratio!!First convert the grams to moles……75g H2 x 1moleH2 / 2.02g H2
12 Next use molar ratio….. 75g H2 x 1mole x 1mole N2 2.02g H2 3mole H2 Now you’ve converted to moles of N2, make the final conversion into grams!!!75g H2 x 1mole x 1mole N2 x 28g N22.02g H mole H mole N2
13 75g H2 x 1mole H2 x 1mole N2 x 28g N2 2.02g H2 3mole H2 1mole N2 = 346.5g = 350g of N2
14 1 N2 + 3 H2 2 NH3 If 75g of hydrogen reacts, B) How many g of NH3 are formed? 75g H2 x 1mole H2 x 2mole NH 3 x g NH32.02g H mole H mole NH3MOLAR RATIO:3mole H2 : 1mole N2 : 2mole NH 3= 420g NH3
15 Use the same system for these Mass - Volume StoichiometryInstead of converting the moles of unknown to grams you convert to volume (L)Volume - Volume - StoichiometryInstead of using the molar ratio you use volume ratio and solve for volumeRules remain the same.Just use these differences and when dealing with mass of gas STP comes in
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