4Mole RatiosIn a nutshell: How many moles of one (product or reactant) will you need/receive if you are given one amount of another?(confused? Let’s do an example!)What is the molar ratio between magnesium and hydrochloric acid?
5Mole Ratios What are all possible mole ratios for the following? How might these be useful?
6Stoichiometry!Ratios of moles in a chemical equation can be used as conversion factorsIn the above reaction, how many grams of magnesium will you need to react with 2.00 moles of hydrochloric acid?
7Practice!Determine all of the possible mole ratios for each of the following unbalanced reactions.___Ba(ClO3)2 ___BaCl2 + ___O2___Ca + ___H2O ___Ca(OH)2 + ___H2___MgCl2 ___Mg + ___Cl2___ Fe + ___Cu(NO3)2 ___Fe(NO3)2 + ___Cu___KOH + ___H2SO4 ___K2SO4 + ___H2O___Mg + ___O2 ___MgO___AgNO3 + ___NaCl ___AgCl + ___NaNO3___C2H6 + ___O2 ___CO2 + ___H2O
8Stoichiometry These should be set up as unit conversions! These types are extremely important for determining the amount of product you should have at the end of an experimentLet’s practice!
9PracticeYou have grams of iron (II) sulfide, which you use as a reactant in the following formula equation:FeS + HCl FeCl2 + H2SHow much hydrochloric acid is needed in this reaction? Give your answer in grams.How much of each product is produced (in grams)?When methane combusts, there are grams of oxygen gas available. How much methane is consumed in the reaction? How much of each product is produced (in grams)?
11Limiting Reactants Limiting reactant – Excess reagent – Limiting reactants occur whenever you do NOT have an ideal stoichiometric calculation.
12Limiting Reactants Step 1 – convert everything to moles Step 2 – balance formula equationStep 3 – compare molar values to the balanced chemical equationsStep 4 – determine the limiting reactant!Step 5 – calculate the amount of the second reactant neededStep 6 – subtract the amount of excess reactant needed from the excess amount available (this is your excess!)Step 7 – determine the amount of products produced based on your limiting reactant (use stoichiometry!)
13Limiting Reactant - example Silicon dioxide (quartz) is usually quite unreactive, but readily reacts with hydrogen fluoride according to the following equation.SiO2 (s) + HF(g) SiF4 (g) +2H2O (l)If 6.0 moles of hydrogen fluoride are added to 4.5 moles of silicon dioxide, which is the limiting reactant?
14More practice – class work Some rocket engines use a mixture of hydrazine, N2H4, and hydrogen peroxide, H2O2, as the propellant. The formula equation is given by the following equation.N2H4(l) + H2O2(l) N2(g) + 4H2O (g)Which is the limiting reactant in this reaction, when moles of N2H4 is mixed with moles of hydrogen peroxide?How much of the excess reactant, in moles, remains unchanged?How much of each product, in moles, is formed?
15More Practice!The black oxide of iron, Fe3O4, occurs in nature as the mineral magnetite. This substance can also be made in the laboratory by the reaction between red-hot iron and steam according to the following equation.Fe(s) + H2O (g) Fe3O4 (s) +H2 (g)When 36.0 g of steam are mixed with 67.0 grams of iron, which is the limiting reactant?What mass in grams of black iron oxide is produced?What mass in grams of excess reactant remains when the reaction is completed?
16Percent Yield Percent Yield Example: Chlorobenzene, C6H5Cl, is used in the production of many important chemicals, such as aspirin, dyes, and disenfectants. One industrial method of preparing chlorobenzene is to react benzene, C6H6, with chlorine, as represented by the following equation.C6H6(l) + Cl2 (g) C6H5Cl (l) + HCl (g)When 36.8 grams of benzene reacts with excess chlorine gas, the actual yield of chlorobenzene is 38.8 grams. What is the percentage yield of chlorobenzene?Step 1: balance equationStep 2: Determine molecular weightsStep 3: Determine theoretical yieldStep 4: Determine percent yield = 73.2 %