Compound from chemical formulas

Find the simplest formula of a compound from chemical analysis. 

C09-0083. Fluorine forms compounds whose chemical formula is XF4 with elements from groups 14, 16, and 18. Determine the Lewis structure, describe the shape, and draw a ball-and-stick model of Gep4, SeF4, and Xep4. 

For H35C1, a)e = 2,989cm 1 and n is 0.9799. Then, its K is 5.16 x 105 (dynes/cm) or 5.16 (mdyn/A). If such a calculation is made for a number of diatomic molecules, we obtain the results shown in Table 1-3. In all four series of compounds, the frequency decreases in going downward in the table. However, the origin of this downward shift is different in each case. In the H2 > HD > D2 series, it is due to the mass effect since the force constant is not affected by isotopic substitution. In the HF > HC1 > HBr > HI series, it is due to the force constant effect (the bond becomes weaker in the same order) since the reduced mass is almost constant. In the F2 > Cl2 > Br2 > I2 series, however, both effects are operative the molecule becomes heavier and the bond becomes weaker in the same order. Finally, in the N2 > CO > NO > 02, series, the decreasing frequency is due to the force constant effect that is expected from chemical formulas, such as N=N, and 0=0, with CO and NO between them. 

The meaning of a chemical formula was discussed in Chapter 5, and we learned how to interpret formulas in terms of the numbers of atoms of each element per formula unit. In this chapter, we will learn how to calculate the number of grams of each element in any given quantity of a compound from its formula and to do other calculations involving formulas. Formula masses are presented in Section 7.1, and percent composition is considered in Section 7.2. Section 7.3 discusses the mole—the basic chemical quantity of any substance. Moles can be used to count atoms, molecules, or ions and to calculate the mass of any known number of formula units of a substance. Section 7.4 shows how to use relative mass data to determine empirical formulas, and the method is extended to molecular formulas in Section 7.5. 

Much confusion in the literature on this subject has been due to the placing of too much reliance on magnetic data of dubious quality and to incorrect deductions of coordination numbers from chemical formulae. There are regrettably few examples of compounds of which both thorough magnetic and structural studies have been made. The following facts have been established ... 

DENDRAL uses a set of rule-based methods to deduce the molecular structure of organic chemical compounds from chemical analysis and mass-spectrometry data. This process includes detecting structural fragments, generating structural formula from these fragments, and verifying it by determining the correlation between... 

Follow these steps for writing formulas for binary covalent compounds when you are given a systematic name. Notice that they are the reverse of the steps for writing names from chemical formulas. 

To complete these steps, we need one additional kind of conversion factor that converts between moles of an element and moles of a compound containing that element. We obtain this conversion factor from the compound s chemical formula. For example, the formula for hexane, C6H14, tells us that each hexane molecule contains six... 

Names and formulas of compounds form the vocabulary of the chemical language. In this discussion, you ll learn the names and formulas of ionic and simple covalent compounds and how to calculate the mass of a unit of a compound from its formula. 

I use standard chemical nomenclature to deduce the names of simple inorganic compounds from their formulas or vice versa. 

Add Names from Anion Names 57 Binary Covalent Compounds 58 The Simplest Organic Compounds Straight-Chain Alkanes 58 Molecular Masses from Chemical Formulas 59... 

The mass percent composition of a compound indicates each element s percentage of the total compound s mass. The mass percent composition can be determined from the compound s chemical formula and the molar masses of its elements. 

Two-Dimensional Representation of Chemical Structures. The lUPAC standardization of organic nomenclature allows automatic translation of a chemical s name into its chemical stmcture, or, conversely, the naming of a compound based on its stmcture. The chemical formula for a compound can be translated into its stmcture once a set of semantic rules for representation are estabUshed (26). The semantic rules and their appHcation have been described (27,28). The inverse problem, generating correct names from chemical stmctures, has been addressed (28) and explored for the specific case of naming condensed benzenoid hydrocarbons (29,30). 

The formula weight of an element (or a compound or a species) is obtained as the sum of the weight contributions from the constituent atoms making up its chemical formula. The formula weight of an element is its atomic weight and that of a compound is its molecular weight. 

To this point, our study of chemistry has been largely qualitative, involving very few calculations. However, chemistry is a quantitative science. Atoms of elements differ from one another not only in composition (number of protons, electrons, neutrons), but also in mass. Chemical formulas of compounds tell us not only the atom ratios in which elements are present but also the mass ratios. 

The formulas of ionic compounds have a different meaning from those of molecular compounds. Each crystal of sodium chloride has a different total number of cations and anions. We cannot simply specify the numbers of ions present as the formula of this ionic compound, because each crystal would have a different formula and the subscripts would be enormous numbers. However, the ratio of the number of cations to the number of anions is the same in all the crystals, and the chemical formula shows this ratio. In sodium chloride, there is one Na+ ion for each Cl ion so its formula is NaCl. Sodium chloride is an example of a binary ionic compound, a compound formed from the ions of two elements. Another binary compound, CaCl2, is formed from Ca2+ and Cl- ions in the ratio 1 2, which is required for electrical neutrality. 

If the chemical formula of a compound is already known, its mass percentage composition can be obtained from the formula. 

The written name of a compound includes the names of the elements it contains and information about the numbers of atoms of each element. The elements have to occur in some order, and this order is set by the same guidelines as for the chemical formula (see Section 3-11. Names can contain element names, roots derived from element names, and prefixes indicating the number of atoms of each element. Tables and 3 list the more important roots and prefixes that appear in the names of binaiy compounds. We can summarize the rules for naming binary compounds in three guidelines ... 

Ionic compounds are named using the same guidelines used for naming binary molecules, except that the cation name aiways precedes the anion name. Thus, NH4 NO3 is ammonium nitrate, Na2 CO3 is sodium carbonate, and Ca3 (P04)2 is caicium phosphate. The subscripts are not specified in these names because the fixed ionic charges determine the cation-anion ratios unambiguously. Example 3-6 reinforces these guidelines by showing how to construct chemicai formulas from chemical names. 

From the chemical formulas, we might expect similar names for these compounds, but notice that they fall into three classes with different rales for each class PCI3 and GeCl4 do not contain metals, MgCl2 contains a metal that forms a unique cation, while C0CI3, S11CI2, and S11CI4 contain metals with more than one stable cation. 

Many ionic compounds can have water molecules incorporated into their solid structures. Such compounds are called hydrates. To emphasize the presence of discrete water molecules in the chemical structure, the formula of any hydrate shows the waters of hydration separated from the rest of the chemical formula by a dot. A coefficient before H2 O indicates the number of water molecules in the formula. Copper(II) sulfate pentahydrate is a good example. The formula of this beautiful deep blue solid is C11SO4 5 H2 O, indicating that five water molecules are associated with each CuSOq unit. Upon prolonged heating, CuSOq 5 H2 O loses its waters of hydration along with its color. Other examples of hydrates include aluminum nitrate nonahydrate, A1 (N03)3 9 H2 O,... 

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