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Stoichiomerty

Stoichiomerty. By Jessica, Jeffrey and Bruno. What is Stoichiometry. Stoichiomerty deals with chemical reactions that have to do with quantities of substances. It also deals with balanced equations with units between one substance with another. Mole Ratio.

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Stoichiomerty

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  1. Stoichiomerty By Jessica, Jeffrey and Bruno

  2. What is Stoichiometry • Stoichiomerty deals with chemical reactions that have to do with quantities of substances. • It also deals with balanced equations with units between one substance with another.

  3. Mole Ratio • The mole ratio uses coefficients to convert moles from one substance to another. • To convert the moles, you need to know the amount of moles in the problem. • To solve. You use the coefficients from the balanced equation to put the known substance on top and the unknown at the bottom and then multiply. Ex.(5mol/? mol)

  4. Solving the Problem • To solve the problem, you need to convert whatever substance from another substance from a balanced equation. Ex. Volume to grams to mol to mol to grams to volume. • There are 5 conversion including 2 densities, 2 molar masses, and a mole ratio.

  5. The Steps • Step 1: Change whatever units that are given to you into moles. • Step 2 : Use the mole ratio to determine how many moles are their in a substance. • Step 3: Change out of the moles into the unit you need to solve the problem.

  6. Number of… • Volume- you use the molar mass & density. • In order to convert volume to mass (or mass to volume) simply use the density as a conversion factor for the problem. • Particles- You use the Avogadro’s # 6.022x10(23).

  7. Limiting Reactant & Excess Reactant • The Limiting Reactant is the substance controlling the quantity of the product forming in a chemical reaction. • It is used up first by the chemical reaction. • The Excess Reactant is the substance not used up completely in a chemical reaction. • The Excess Reactant will have some of the substance left over.

  8. Theoretical Yield • The Theoretical Yield is the maximum quantity of a product that a reaction can work perfectly. • In order to get the theoretical yield, you must find the limiting reactant first. Ex. ?HCl of (1mol of h2o/137.32g of h2o) X (1mol of hcl/1mol of h2o) 225g (82.g of hcl/ 1 mol

  9. Actual Yield • The Actual Yield is the mass of the product and the measured amount of a reaction. • The actual yield is used less the theoretical yield because some products turn back into a reactant. Ex. 80.5% =actual yield _____________ x 100 4808g • You divide the number then multiply by 100. Then you have to divide by grams.

  10. Percentage Yield • The Percentage yield is used to describe the efficiency of a chemical reaction. Ex. % yield = 591g(actual yield) --------------------------------- * 100 = 80.1% 738g (theoretical yield)

  11. Safety Air bags in Stoichometry • In order to design an air bag, the designers use stoichomerty for help. • The air bag designers must make sure that the bag does not overinflate or under inflate. • The chemicals in the bag must also be in the right proportion.

  12. Stiochiometric Precision • To create an air bag, many materials are used. • For example, a mixture of gas generants that is a solid of NaN3 & an oxidizer. • The gas used inside the bag to inflate it is pure nitrogen gas which makes this reaction 2NaN3 (s) ------ 2Na(s) + 3N2 (g). • The reaction cannot inflate the bag because the reaction is to strong ,so the oxidizer Fe2o3 are in the reaction.

  13. Stoichiometry and pollution • To have the right efficiency of a car’s engine, you’d need the stoichiometric ratio. • The Atmosphere is polluted by cars so the Clean Air Act was enacted in 1968 to address the smog of pollution in the air. • Due to high temperatures inside the engine, forms highly reactive nitrogen oxides NO and NO2 • N2(g)+O2(g)2NO(g) Causes Pollution 2NO(g)+O2(g)2NO2(g)

  14. Meeting the legal limits of stoichiometry • Automobiles manufactures use stoichiometry to predict when adjustments will be necessary to keep exhaust emissions within legal limits. • Auto manufactures must decide how much fuel the vehicle will burn to go a certain distance. • Automobiles with better gas mileage will use less fuel per kilometer resulting In lower emissions per kilometer.

  15. Catalytic converters can help • Cars built in the U.S are also built with catalytic converters. • They also speed up the change of CO into CO2 • They also speed up the change of unburned hydrocarbons into CO2. • It is important that unburned fuel does not come out of the exhaust. • Catalytic converters perform their best when the exhaust gas is hot and also when the air to fuel ratio is close to the proper stoichiometric ratio.

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