True formula

Since the actual number of protons transferred between the analyte and titrant is uncertain, we define the analyte s equivalent weight (EW) as the apparent formula weight when = 1. The true formula weight, therefore, is an integer multiple of the calculated equivalent weight. 

First, follow the four-step process for finding the empirical formula. Then compare the empirical formula with the molar mass information to find the true formula. 

For standardizing a base solution, primary standard grade potassium biphthalate is a popular choice. Also called potassium hydrogen phthalate, potassium acid phthalate, or simply KHP, it is the salt representing partially neutralized phthalic acid and is a monoprotic weak acid. The true formula is KHC8H404. Figure 5.8 shows the chemical structure of phthalic acid and KHP. The reaction with a base is as follows ... 

CN checking number AA reference number (cf Table 8.13) i position number of the respective aa within the sequence (i of the N-terminal aa is 1) NR total number of aa within the polypeptide chain Mr molar mass of the polypeptide COMP true formula of the polypeptide (all naturally occurring aa have to be listed, aa which are no part of the chain are indicated by 0 ). 

If you are certain that the true formula of the 1-2-3 superconductor is VBa2CujOr.11 with 0.0 < B < 0.4, what does that imply concerning ihe copper atoms ... 

If the empirical formula ofthis compound had been found to be (CH2F)j., this mole weight determination could be used to find the true formula. The mole weight of the CH2F unit is 33.0. The true mole weight must be some integral multiple U)of 33.0 ... 

We recall from Chapter 10 that the percentages of the elements in a compound can be used to compute the simplest formula for the compound. When the substance is soluble in some suitable liquid, we can combine the empirical formula with a molecular-weight determination by freezing-point depression to get the true formula. 

Using the methods of Chapter 10, we find the empirical formula to be C3H2C1. jf this were the true formula, the molecular weight would be 73.5. The freezing point depression gives a molecular weight of approximately 150. This is not an accurate value, for the experimental measurement is subject to some error, but it indicates that the true molecular weight is near 150. 

I When 0 532 g of a certain solid organic compound is dissolved in 16 8 g of urethane, whose freezing point is 49 50°C, the freezing point of the solution is lowered to 48 32°C Chemical analysis shows this compound to be 69 5% C, 7 25% H, and 23 25% O Determine the true formula of this compound... 

AO 356 g sample of a solid organic compound, when dissolved in 9 15 ml of carbon tetrachlonde (density = 1 595 g/ml), raises the boiling point of the carbon tetrachlonde by 0 560°C When analyzed, this compound is found to be 55 0% C, 2 75% H, 12 8% N, and 29 4% O What is the true formula of this compound9... 

By analysis, a certain solid organic compound is found to be 40 0% C, 6 1% H, and 53 3% O When a 0 650 g sample of this compound is dissolved m 27 80 g of diphenyl, the freezing point is lowered by 1 56°C Determine the true formula of this compound... 

The determination of the empirical formula of a compound can be made experimentally, by determining the percentage amounts of elements present in the substance using the methods of quantitative chemical analysis. At the same time the relative molecular mass of the compound has to be measured as well. From these data the empirical formula can be determined by a simple calculation. If, for some reason, it is impossible to determine the relative molecular mass the simplest (assumed) formula only can be calculated from the results of chemical analysis the true formula might contain multiples of the atoms given in the assumed formula. 

In monoclinic (Pn = C ) RbNb[B03]2, octahedra chains of NbOg are tilted in the a-direction (100) the true formula is RbNbpOjk Isotypic are RbTapOjk and TlTalBOjlj orthorhombic (Pna2j = C, ) TlNbfBOjjj has a similar, but different structure 3 3) ... 

There remains a variety of unstable, insoluble, or incompletely characterized complexes whose true formulas remain open to speculation. Many unstable 1 1 complexes between copper (I) halides and ammonia (31) or the lower aliphatic amines (71, 281, 336) have been studied manometrically, but the compounds formed have high dissociation pressures, and attempts to isolate them have been unsuccessful owing to loss of ligand or to oxidation. Complexes with higher amines (348) or with pyridine (334) and its oligomers (178, 229, 230) are, in... 

This reaction, however, yields a compound containing a hydroxyl group instead of a carbonyl group and the question is which is the true formula and which represents the constitution of aceto acetic ester The answer, strange as it may seem, is that both are right for we have reactions some of which prove one and some the other constitution. 

Since they were obtained as sirups, the acetylated L-sorbose methyl and ethyl orthoacetates have not been investigated further. Their true formulas are unknown at present. 

If you did not know the true formulas for carbon monoxide and carbon dioxide, what information would you need beyond what is provided in the illustration in order to calculate them ... 

Empirical formulas are the simplest chemical formulas they are written by re-dncing the subscripts in molecnlar formnlas to the smallest possible whole numbers. Molecular formulas are the true formulas of molecules. As we will see in Chapter 3, when chemists analyze an nnknown componnd, the first step is usually the determination of the compound s empirical formnla. 

We can represent this information by the formula CH2O, which expresses the relative numbers of C, H, and O atoms present. Is this the true formula for the compound In other words, is the compound made up of CH2O molecules It may be. However, it might also be made up of C2H 02 molecules, C3Hg03 molecules, C HgO molecules, molecules, CgHj20g... 

The advent of the first metal carbonyl cluster, Fe3(CO)i2, was also long ago. Here again there was long uncertainty about its structure, resolved only by the work of Dahl in 1966, who was also responsible for clarifying the nature of the analogous Ru3(CO)i2 and Os3(CO)i2. During the same period of time Chini and coworkers prepared the first four-atom metal carbonyl cluster, Co4(CO)i2, whose Rh and Ir analogues were soon to follow, and in 1963 Dahl showed the true formula and structure of the first six-atom cluster compounds of the carbonyl type, Rh6(CO)i6. 

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