Limiting reagents and

Fig. 8.9 A typical stoichiometry question on limiting reagents and amount of product formed in a reaction...

In this case the hydrogen is the limiting reagent and equation 3.1.43 gives... 

The butadiene is the limiting reagent and conversions will be expressed in terms of this species. Over the composition range of interest there will always be sufficient methyl acrylate present to tie up the aluminum chloride. Consequently the concentration of the complex (A1C13-M) will remain constant throughout the length of the reactor at a value equal to the initial A1C13 concentration. For these conditions the reaction rate expression is the form... 

Experiments were then designed in which absorbance readings were acquired over the full time course of the reaction. These experiments employed a low concentration of PyO as the limiting reagent and a large excess of phosphine. The data fit a precise pseudo-second-order analysis, and gave kcat = 1.5xl04Lmol 1 s-1 in benzene at 298 K a precision of 5% was estimated. 

A. 81.37% is the percent yield. The question clearly notes that sodium hydroxide is the excess reagent. (Tip You always can ignore a reactant if the problem says it s in excess. That s like a big this-one-isn t-important sign in the problem.) So sulfuric acid is the limiting reagent and is the reagent you should use to calculate the theoretical yield ... 

The first step is to identify the limiting reagent. Simply pick one of the reactants as a trial candidate for the limiting reagent, and calculate how much of the other reagents are required to react completely with the cemdidate. 

D) Na is the limiting reagent and 2.0 moles of NaCl will be produced. 

One of the starting materials (A or B) is a limiting reagent and consequently, unreacted starting material will be left over even in a reaction with 100% yield. 

In the laboratory of T.F. Jamison, the synthesis of amphidinolide T1 was accomplished utilizing a catalytic and stereoselective macrocyclization as the key step. ° The Myers asymmetric alkylation was chosen to establish the correct stereochemistry at the C2 position. In the procedure, the alkyl halide was used as the limiting reagent and almost two equivalents of the lithium enolate of the A/-propionyl pseudoephedrine chiral auxiliary was used. The alkylated product was purified by column chromatography and then subjected to basic hydrolysis to remove the chiral auxiliary. 

Skill 8.7 Solving problems involving limiting reagents and percent yield... 

But there are 20 moles of F2 available, more than needed to completely react with S. Thus S must be the limiting reagent and F2 the excess reagent. The amount of SF produced depends only on how much S was originally present. 

Since there are only 4 moles of S present, we arrive at the same conclusion that S is the limiting reagent and F2 is the excess reagent. 

Since there are only 37.42 moles of NH3 present, not enough to react completely with the CO2, NH3 must be the limiting reagent and CO2 the excess reagent. 

The quantity, nfl — vf) = if, is called the advancement capacity of the ith substance. Clearly, if substance i is a reactant, then — V is positive thus the advancement capacities of the reactants are all positive. If the values of if are all equal, then this common value of if = i°, the advancement capacity of the mixture. If the if are not all equal, then there is at least one smallest value, if. This value identifies the substance as the limiting reagent, and if = i°, the advancement capacity of the mixture. The value of i may not exceed i°, since that would mean that reactant j (and possibly others) would have a negative mole number. Thus, i° is the greatest value of i. 

Chemical stoichiometry is the area of study that considers the quantities of materials in chemical formulas and equations. Quite simply, it is chemical arithmetic. The word itself is derived from stoicheion, the Greek word for element and metron, the Greek word for measure. When based on chemical formulas, stoichiometry is used to convert between mass and moles, to calculate the number of atoms, to calculate percent composition, and to interpret the mole ratios expressed in a chemical formula. Most topics in chemical arithmetic depend on the interpretation of balanced chemical equations. Mass/mole conversions, calculation of limiting reagent and percent yield, and various relationships among reactants and products are commonly included in this topic area. 

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