2 If we have… how many sets can we make? Limiting reactant = the reactant that runs out first causing the reaction to stopExcess reactant = reactant that does not get completely used up during a reactionWith this left overExcess
3 Steps to solve limiting reactants problems Split into 2 problemsSolve each problemPick smallest answerSmallest answer comes from limiting reactantLargest answer comes from excess reactant
4 Calculating product when reactant is limiting If we had 12 moles of nitrogen and 18 moles of hydrogen, what is the maximum number of moles of NH3 that could be produced?N2 + 3H2 2 NH3
5 Calculating product when reactant is limiting If we had 112 grams of nitrogen and 18 grams of hydrogen, what is the maximum number of grams of NH3 that could be produced?N2 + 3H2 2 NH32(14) (1)Remember…NitrogenHydrogenPick lowest numberTherefore Hydrogen is your limiting reactant
6 Calculating product when reactant is limiting With 48 grams of magnesium and 48 grams of oxygen available, how much product can be formed?2Mg + O2 2 MgO(16)OxygenMagnesiumPick lowest numberTherefore Magnesium is your limiting reactant and oxygen is the excess reactant
7 Limiting Reactants Practice III How many grams of sodium chloride can be produced in the following reaction with 150 grams of sodium and 200 grams of chlorine?2Na + Cl2 2 NaCl(35.5)SodiumChlorinePick lowest number
8 Limiting Reactants Practice III In the above reaction, how many more grams of chlorine will be required to fully react with the remaining sodium?We need to figure out how many grams of chlorine is needed to react with 150 grams of sodium2Na + Cl2 2 NaCl(35.5)SodiumChlorine needed = 231 gChlorine given (from problem) = 200 gAdditional Chlorine needed = 31 g
9 Percent YieldActual yield = the actual amount of product formed during an experimentTheoretical yield = amount of product that could be produced according to calculationsPercent yield = ratio of actual and theoretical yield
10 Percent Yield Practice I A student uses stoichiometry to calculate the predicted yield of CO2 in a chemical reaction as 323 g. When the student mixes the chemicals to make the CO2, he finds that the reaction only produces 308 g of CO2. What is the percent yield?
11 In the reaction, how many grams of potassium oxide can be produced with 78 grams of potassium and 140 grams of boron oxide?6 K + B2O3 3 K2O + 2 B(10.8)+3(16) 2(39.1)+16PotassiumBoron OxidePick lower number
12 Problem 2 continuedIf the actual yield from the above reaction was 81 grams, what is the percent yield?Actual yield = 81 gramsTheoretical yield = g (from last slide)
13 Pick lower number N2 + 3H2 2 NH3 3. The actual yield in the above reaction was 39 grams of ammonium. Using 84 grams of nitrogen and 8 grams of hydrogen, what is the percent yield?-first we must calculate the theoretical yield of product which means we need to find our limiting reactantN2 + 3H2 2 NH32(14) (1)NitrogenHydrogenPick lower number
14 Problem 3 continuedActual yield = 39 gramsTheoretical yield = 45.3 g (from last slide)
Your consent to our cookies if you continue to use this website.