Mole-to-coefficient ratio

We calculate the mole-to-coefficient ratio of each reactant by dividing the moles of that reactant by its coefficient in the balanced chemical equation. The reactant that has the smallest mole-to-coefficient ratio is the limiting reactant. Many of us use this method. 

The quantity (mole-to-coefficient ratio) of F2 is smaller than that of I2 therefore, fluorine in the limiting reactant (reagent). Once we know the limiting reactant, all remaining calculations will depend on the limiting reactant. 

Ammonia has a mole-to-coefficient ratio of 1.47, and oxygen has a ratio of 0.625. Because oxygen has the lowest ratio, oxygen is the limiting reactant, and you need to base your calculations on it. 

We have data for the amounts of both starting materials, so this is a limiting reactant problem. Given the chemical equation, the first step in a limiting reactant problem is to determine the number of moles of each starting material present at the beginning of the reaction. Next compute ratios of moles to coefficients to identify the limiting reactant. After that, a table of amounts summarizes the stoichiometry. 

In limiting-reactant problems, don t consider just the number of grams or even moles to determine the limiting reactant—use the mol/coefficient ratio. 

Kg is the experimental distribution coefficient and K g the corrected value. This correction is required, because any measure for the interactions that occur in certain solvents should be more related to the ratio of mole fractions than to the ratio of concentrations of the solute in the liquid phase and in the gas phase. We may assume the molar volume of the gas phase to be constant and hence irrelevant if our purpose is a classification of solvents. However, the molar volumes of solvents vary a great deal. The Kg values for n-octane in various hydrocarbon solvents vary up to a factor of 3.9 between cyclohexane and squalane [216]. The Kg values vary by a more realistic factor of 1.5 [214]. 

A mole ratio is the ratio of the number of moles of one substance to the number of moles of another substance. Because coefficients can represent moles, molecules, or atoms, you can think of a mole ratio as a coefficient ratio. For example, look at the equation for aluminum oxide, 4A1 + 302 —> 2Al203. You can pick any two substances from the equation and determine their mole ratio. The mole ratio of Al to Al203 is 4 2 or 2 1, while the mole ratio of 02 to Al203 is 3 2. This leads to another type of problem that you might encounter. Suppose you were asked to produce 1,000 moles of Al203 for a big chemical company. How much aluminum and oxygen would you need to purchase Start with the balanced equation 4A1 + 302 — 2Al203. 

Gay-Lussac s law of combining volumes relates the volumes of gases involved in a reaction, all measured separately at the same temperature and pressure. The volume ratio under these conditions is equal to the mole ratio and, therefore, to the ratio of coefficients in the balanced chemical equation (Section 12.9). 

More recently, Albery et al. [203] carried out an improved analysis of experimental data for dilute acidic solutions which was based on an extension of McCauley and King s treatment [204] of kinetic data for the reaction of diazoacetone with water and halide ions. Albery et al. determined rate coefficients as well as product ratios, p - (moles ethyl halogenoacetate formed)/(moles ethyl glycollate formed), with the aid of UV spectrophotometric and gas—liquid chromatographic methods. In eqn. (48), the logarithms of the activity coefficient ratios were considered to be linearly dependent on the ionic strength, viz. 

The fact that O atom consumption exceeded H2S consumption by 10-20 % was taken as further evidence for such a chain mechanism. The measured rate coefficient for the overall reaction of 0-1- H2S was found to be 1.2 x 10 l.mole" .sec The ratio of hydrogen produced to H2S consumed gives the ratio of the rate of the chain mechanism, reactions (29) and (30), to the overall rate, reactions (28), (29) and (30)... 

The mixture is stirred until the desired degree of haptenation is obtained. This can be determined by measuring the absorbance at 360 nm. For simplicity, this absorbance can be assumed to be due solely to DNP-lysine groups, the molar extinction coefficient of which is 17530. Thus, the (moles of DNP)/(moles of protein) ratio can be calculated from the expressions (using the law of Lambert Beer Section 9.2.3.4) ... 

General Steps Use a unit analysis format. Set it up around a mole-to-mole conversion in which the coefficients from a balanced equation are used to generate a mole ratio. (See Figure 10.1 for a summary.) The general steps are... 

First, however, we convert from mass of C2H5OH to moles, using the compound s molar mass. Then we set up the mole-to-mole conversion, using the molar ratio of ethanol to carbon dioxide derived from the coefficients in the balanced equation. The next step is the new one we use the molar volume at STP to convert from moles of CO2 to volume of CO2 at STP. The sequence as a whole is... 

The coefficients in the copper-silver nitrate equation were fairly easy to use and you may have quickly reasoned that the mole of Ag(s) would be twice that of Cufo) because of the 1 to 2 coefficient ratio, but when the coefficients are more complicated than those in this problem, the conversion equation allows a quick route to the answer. A similar conversion equation using sought and known terms was presented in Chapter 1 to convert units of measurement, and in Chapter 5 for mole-to-mass and mass-to-mole conversions. 

The 1 -to-1 coefficient ratio of the balanced equation tells that the number of moles of CO2(g) produced will be identical to the number of moles ofCaC03(s) decomposed. 

Note that the mole fractions of L-asparagine in each of the solvents is so low that we can assume the activity coefficient ratio we have obtained to be that at infinite dilution. Therefore,... 

It is also possible to use mole (or mass) ratio driving forces rather than mole fractions provided that the mass transfer coefficients are in the corresponding units. The mole ratio-based mass transfer coefficients are approximately related to kc by... 

You are given the volume, pressure, and temperature of a gas sample. The mole and volume ratios of gaseous reactants and products are given by the coefficients in the balanced chemical equation. Volume can be converted to moles and thus related to mass by using molar mass and the ideal gas law. 

Contents of the gas components is determined as the product of volume fraction of each of them and the value of the gas/water ration (line 2). Bunsen solubility coefficients (hne 3) and Sechenov coefficients (line 4) for temperature 40 °C may be taken from Tables 2.28 and 2.29. Corrections of Bunsen solubihty coefficients for the salinity (m =118/58 =2.03 mole-1" 0 are calculated from equation (2.306) (line 5). Partial pressure of each component is equal to the ratio of its concentration and the value of corrected Bunsen solubility coefficient (hne 6). 

In general, in the absence of any information on the activity coefficient ratio, preference should be given to supersaturations based on molal units because of their more practical utility compared with mole fractions and their temperature independence compared with molar units. In other words, a concentration scale based on mass of solvent is generally preferred to one based on volume of solution. 

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