Formula weight conversions with

Ans. There are 6.02 X 10 i atoms in 1.00 mol Na (Avogadro s number). There is 23.0 g of Na in LOO mol Na (equal to the atomic weight in grams). This problem requires use of two of the most important conversion factors involving moles. Note which one is used with masses and which one is used with numbers of atoms (or molecules of formula units). With numbers of atoms, molecules, or formula units, use Avogadro s number with mass or weight use the formula weight. 

What does 1 ppm represent in terms of moles per liter It depends on the formula weight, but the approximate relationship between concentrations in parts per million (or parts per billion) and in moles per liter can be seen by assuming a formula weight of 100 for an analyte. Then, since 1 ppm = 10 g/L, it is equal to (10 g/L) (10 g/mol) = 10 mol/L. Similarly, 1 ppb = 10 mol/L. Note that this latter concentration is smaller than the hydrogen ion concentration in pure water (10" mol/L) Of course, this relationship is approximate and will vary with the formula weight. One part per million solutions of zinc and copper, for example, will not be the same molarity. Conversely, equal molar solutions of different species will not be equal in terms of ppm unless the formula weights are equal. The former concentration is based on the number of molecules per unit volume, while the latter is based on the weight of the species per unit volume. 

Formula weight 187.44. Very slightly soluble in water, slowly reacts with dilute mineral acids. Corundum structure (D51 type). Heating at 600°C in air produces slow monotropic conversion to iS-GasOa. On heating in an autoclave under water vapor above 305°C converts to /S-GaaOg, below305°C, to GaO(OH) (see above), d 6.44. 

If, for example, 2 mol of diamine is reacted until complete conversion (pcooH = 1) with a mol of dicarboxyUc acid (ro = 0.5), then the number-average degree of polymerization is X = 3, in accordance with equation (17-24), and the mass-average degree is Xw— 5, in accordance with equation (17-38). Following from Equation (17-40), however, the diamide will only be formed up to 25% by weight (w, = 0.25), so that the yield of this compound can only reach 25% of the theoretical formula molar conversion (Table 17-4). 

A gravimetric factor is a number used to convert, by multiplication, the weight of one chemical to the weight of another. Such a conversion can be very useful in an analytical laboratory. For example, if a recipe for a solution of iron calls for 55 g of FeCl3 but a technician finds only iron wire on the chemical shelf, he or she would want to know how much iron metal is equivalent to 55 g of FeCl3 so that he or she could prepare the solution with the iron wire instead and have the same weight of iron in either case. In one formula unit of FeCl3, there is one atom of Fe, so the fraction of iron(III) chloride that is iron metal is calculated as follows ... 

In the field of selective hydrogenation two important properties are used to describe the catalytic performance the activity and the selectivity of the catalysts. Their values have to be optimized. The simplest approach is to fix the desired conversion level and ranking the catalysts according to their selectivity data. An alternative way for catalyst optimization is the use of the so called "desirability function" d. Upon using this function different optimization parameters can be combined in a common function Dj. In the combination different optimization parameters (often called as objective functions) can be taken into account with different weights [21]. The single desirability function for the conversion (a) can be described by the following formula ... 

It is difficult to obtain an accurate measure of renal function in patients with cirrhosis. A number of studies have shown that they tend to have low serum creatinine levels. This has been explained by a reduced muscle mass in cirrhotic patients and a reduced conversion of creatine to creatinine [10]. The calculation of creatinine clearance using the Cockcroft and Gault formula is also inaccurate in predicting GFR in these patients because it uses the serum creatinine level (which may be falsely low) and body weight in the calculation, which is likely to be inflated due to the presence of ascites [12]. The measured creatinine clearance, based on urinary excretion of creatinine, should theoretically be more accurate, even in patients with reduced muscle mass or impaired creatinine synthesis. However, it has been shown that this also overestimates the GFR because of an increased fractional tubular secretion of creatinine in cirrhotic patients, particularly those with reduced GFR [10]. 

Near the begnning of our study (Sec. 3.32), we outlined the general steps an organic chemist takes when he is confronted with an unknown compound and sets out to find the answer to the question that is it We have seen, in more detail, some of the ways in which he carries out the various steps determination of molecular weight and molecular formula detection of the presence—or absence—of certain functional groups degradation to simpler compounds conversion into derivatives synthesis by an unambiguous route. 

It has been known for several years through in vivo tracer studies that human term and preterm infants are capable of synthesizing C20 and C22 LCP from the Cjg precursors (Carnielli et al., 1996 Salem et al., 1996 Sauerwald et al., 1997). These and more recent studies suggest that this capability is highly variable from individual to individual (Uauy et al., 2000). However, all studies to date have sampled blood compartments, and estimates of relative conversion based on such measurements are tenuous at best. We recently reported the bioequivalence of dietary LN A and DHA as precursors for primate neonate brain DHA accretion based on direct measurements of brain DHA accretion (Su et al., 1999a). Neonate baboons were fed a commercial infant formula with 18% of total fatty acids by weight as LA and 1.8% as LNA, which gives an LA/LNA ratio of 10 for 6 wk. Doses of LNA or DHA were administered orally at 4 wk and animals were sacrificed at 6 wk. 

As we saw with mass and moles of elements and molecular compounds, it is important to be able to convert between mass and moles of ionic substances. The development of the tools for this conversion starts with the determination of the formula mass, which is the weighted average of the masses of the naturally occurring formula units of the substance. (It is analogous to the atomic mass for an element and the molecular mass for a molecular substance.)... 

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