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STOICHIOMETRY Mass relationship of reactants and products in a chemical reaction

STOICHIOMETRY Mass relationship of reactants and products in a chemical reaction. Hydrogen gas + nitrogen gas ----> ammonia gas Qualitative: describes the “nature” of the reactants and products Quantitative: describes the amounts of reactants and products.

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STOICHIOMETRY Mass relationship of reactants and products in a chemical reaction

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  1. STOICHIOMETRYMass relationship of reactants and products in a chemical reaction • Hydrogen gas + nitrogen gas ----> ammonia gas • Qualitative: describes the “nature” of the reactants and products • Quantitative: 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 ratio • Convert 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 1 sandwich OR….. 2B + 2M + 1C + 3P 1B2M2CP3

  5. 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 B2M2CP3 MEAT: 8M = 4 B2M2CP3 CHEESE: 4C = 4B2M2CP3 PICKLES: 12P = 4 B2M2CP3 EVALUATION: 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 )= 20B MEAT: 10B2M2CP3 x (2M / B2M2CP3 )= 20M CHEESE: 10B2M2CP3 x (1C / B2M2CP3 )= 10C PICKLES: 10B2M2CP3 x (3P / B2M2CP3 )= 30P THUS: 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 sandwiches • In any reaction you will likely have a limiting reagent AND an excess reagent. • Too little of one • Too much of the other

  8. 3 H2 + 1N2 2NH3 • What do the coefficients mean? • 3 molecules : 1 molecule : 2 molecules • OR 3moles : 1mole : 2moles

  9. 1N2 + 3H2 2NH3 1 molecules : 3 molecules : 2 molecules 10 molecules : 30 molecules : 20 molecules 100 molecules : 300 molecules : 200 molecules 1 (6x1023) : 3 (6x1023) : 2 (6x1023) 1 MOLE : 3 MOLE : 2 MOLE

  10. 1N2 + 3H22NH3 1mole of : 3mole of : 2mole of N2molecules H2molecules NH3 molecules This is the MOLAR RATIO allowing 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 N2 2.02g H2 3mole H2 1mole N2

  13. 75g H2 x 1mole H2 x 1mole N2 x 28g N22.02g H2 3mole H21mole N2 = 346.5g = 350g of N2

  14. 1 N2 + 3 H2 2 NH3If 75g of hydrogen reacts,B) How many g of NH3 are formed? 75g H2 x 1mole H2 x 2mole NH 3x17g NH3 2.02g H2 3mole H2 1mole NH3 MOLAR RATIO: 3moleH2:1mole N2 : 2mole NH 3 = 420g NH3

  15. Use the same system for these • Mass - Volume Stoichiometry • Instead of converting the moles of unknown to grams you convert to volume (L) • Volume - Volume - Stoichiometry • Instead of using the molar ratio you use volume ratio and solve for volume

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