Reacting quantities and the mole

The quantity is known as the extent of reaction. If the system does not react, then the extent of reaction equals zero (i.e., = 0), and the mole numbers are equal to their initial value (i.e.,... 

The coefficients in this equation show that two moles of Sb (243.6 g) react with exactly three moles of I2 (761.4 g) to form two moles of Sbl3 (1005.0 g). Put another way, the maximum quantity of Sbl3 that can be obtained under these conditions, assuming the reaction goes to completion and no product is lost, is 1005.0 g. This quantity is referred to as the theoretical yield of Sbl3. 

For every reaction, there is a certain minimum energy that molecules must possess for collision to be effective. This is referred to as the activation energy. It has the symbol a and is expressed in kilojoules/mol. For the reaction between one mole of CO and one mole of NOfc a is 134 kj/mol. The colliding molecules (CO and N02) must have a total kinetic energy of at least 134 kj/mol if they are to react The activation energy for a reaction is a positive quantity (Ea > 0) whose value depends on the nature of the reaction. 

The reaction between hydrogen gas and oxygen gas proceeds more quickly if we mix the gases and then ignite the mixture with a spark. A violent explosion results. Even so, the quantity of product, water, and the heat evolved are the same per mole of hydrogen reacting as in controlled burning. 

The pragmatic consideration is that if a student were to undertake this reaction, then it would be important to react corresponding amounts of the two reactants. Amount here implies the number of moles, and the unbalanced version of the equation would imply that equal volumes of reactant solutions (if the same concentration) were needed, when actually twice as much alkali solution would be needed as acid solution because the acid is dibasic. The principled point is that the equation represents a chemical process, which is subject to the constraints of conservation rules matter (as energy) is conserved. In a chemical change, the elements present (whether as elements or in compounds), must be conserved. A balanced equation has the same elements in the quantities represented on both sides ... 

When two substances react, they react in exact amounts. You can determine what amounts of the two reactants are needed to react completely with each other by means of mole ratios based on the balanced chemical equation for the reaction. In the laboratory, precise amounts of the reactants are rarely used in a reaction. Usually, there is an excess of one of the reactants. As soon as the other reactant is used up, the reaction stops. The reactant that is used up is called the limiting reactant. Based on the quantities of each reactant and the balanced chemical equation, you can predict which substance in a reaction is the limiting reactant. 

The atomic proportions of magnesium are not related to the mole quantity of hexachlorobenzene in this or any other entrainment reaction. The excess magnesium (1.1 g. atoms in this case) is used to react with ethylene bromide and leave 0.5 g. atom of dean-surfaced magnesium. Ordinarily 1 mole of entrainment reagent is used per mole of inert halide, but for this preparation 2 moles of entrainment reagent per mole of halide gives a better yield. 

As before, p is the fraction of functional groups that have already reacted (see Eq. 4.1), i.e., the mols of ester groups formed (Nq and N are the numbers of functional groups present at the start and a given time of the reaction, respectively), (1 -p) the molar quantity of unreacted hydroxy and carboxy groups, and is the mole fraction of water present in the reaction mixture. Solving Eq. 4.5 for p we obtain the upper limit of conversion as a function of the ratio p = Klriy -. 

The initial solution contains an unknown quantity of cyclohexene and a large amount of Br. When Reaction 17-7 has generated just enough Br2 to react with all the cyclohexene, the moles of electrons liberated in Reaction 17-7 are equal to twice the moles of Br2 and therefore twice the moles of cyclohexene. 

Atoms and molecules react in specific ratios. In the laboratory, however, chemists work with bulk quantities of materials, which are measured by mass. Chemists therefore need to know the relationship between the mass of a given sample and the number of atoms or molecules contained in that mass. The key to this relationship is the mole. Recall from Section 7.2 that the mole is a unit equal to 6.02 X 1023. This number is known as Avogadro s number, in honor of Amadeo Avogadro (Section 3-3). 

The balanced chemical equation for this reaction shows that 1 mol of nitric acid reacts with 1 mol of sodium hydroxide. If equal molar quantities of nitric acid and sodium hydroxide are used, the result is a neutral (pH 7) aqueous solution of sodium nitrate. In fact, when any strong acid reacts with any strong base in the mole ratio from the balanced chemical equation, a neutral aqueous solution of a salt is formed. Reactions between acids and bases of different strengths usually do not result in neutral solutions. 

Phenyl terminated polybutadiene (M 1300 daltons, 45% vinyl) was reacted with trichlorosilane and chloroplatinic acid and then mixed with a slurry of 105 p particle size silica gel having a 250 A average pore diameter in dry toluene for 24 hours. The quantity of trichlorosilane used was 2 mol per mole of polybutadiene. Pyridine was added to remove HCl, and the slurry was gently shaken for 18 hours at ambient temperature. The surface of the silica was blocked by addition of 1,2-bis(trichlor-osilyl)ethane, and the mixture was treated with pyridine. After three hours of shaking the reaction was worked up by vacuum filtration in a sintered glass funnel and washed with toluene and methanol. The modified silica gel was dried in the filter funnel by continued application of vacuum to the filter funnel. 

Because the reactants react in a 1 1 mole ratio, NaOH is in excess, HCl is in limiting quantity, and 0.190 mol of NaCl will be produced. 

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