Moles of compounds

The molar mass of a compound can be calculated from its chemical formula and can be used to convert from mass to moles of that compound. 

You have learned that different kinds of representative particles are counted using the mole. In the last section, you read how to use molar mass to convert among moles, mass, and number of particles of an element. Can you make similar conversions for compounds and ions Yes, you can, but to do so you will need to know the molar mass of the compounds and ions involved. 

Recall that a chemical formula indicates the numbers and types of atoms contained in one unit of the compound. Consider the compound dichlorodifluoromethane with the chemical formula CCI2F2. The subscripts in the formula indicate that one molecule of CCI2F2 consists of one carbon (C) atom, two chlorine (Cl) atoms, and two fluorine (F) atoms. These atom are chemically bonded together. The C-Cl-F ratio in CCI2F2 is 1 2 2. 

Interpret How many of each kind of atom—carbon, chlorine, and fluorine—are contained in 1 mol of CCI2F2  

In some chemical calculations, you might need to convert between moles of a compound and moles of individual atoms in the compound. The following ratios, or conversion factors, can be written for use in these calculations for the molecule CCI2F2. 

But suppose you had a mole of freon. The representative particles would be molecules of freon. A mole of freon would contain Avogadro s number of freon molecules, which means that instead of one carbon atom, you would have a mole of carbon atoms. And instead of two chlorine atoms and two fluorine atoms, you would have two moles of chlorine atoms and two moles of fluorine atoms. The ratio of carbon to chlorine to fluorine in one mole of freon would still be 1 2 2, as it is in one molecule of freon. 

To find out how many moles of fluorine atoms are in 5.50 moles of freon, you would multiply the moles of freon by the conversion factor that relates moles of fluorine atoms to moles of CCI2F2. 

Recall that a mole is Avogadro s number (6.02 x lO S) of particles of a substance. If the substance is a molecular compound, such as ammonia (NH3), a mole is 6.02 X 10 molecules of ammonia. If the substance is an ionic compound, such as baking soda (sodium hydrogen carbonate, NaHCOj), a mole is 6.02 x 10 3 formula units of sodium hydrogen carbonate. In either case, a mole of a compound contains as many moles of each element as are indicated by the subscripts in the formula for the compound. For example, a mole of ammonia (NH3) consists of one mole of nitrogen atoms and three moles of hydrogen atoms. 

You can use the molar mass of a compound to convert between mass and moles, just as you used the molar mass of elements to make these conversions. 

Solving Problems A chemistry Handbook Chemistry Matter and Change 103 

Before you can calculate moles, you must determine the molar mass of water (H2O). A mole of water consists of two moles of hydrogen atoms and one mole of oxygen atoms. 

Now you can use the molar mass of water as a conversion factor to determine moles of water. Notice that 1.000 kg is converted to 1.000 X 10 g for the calculation. 

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Group 13 (IIIA) Perchlorates. Perchlorate compounds of boron and aluminum are known. Boron perchlorates occur as double salts with alkah metal perchlorates, eg, cesium boron tetraperchlorate [33152-95-3] Cs(B(C104)4) (51). Aluminum perchlorate [14452-95-3] A1(C104)2, forms a series of hydrates having 3, 6, 9, or 15 moles of water per mole of compound. The anhydrous salt is prepared from the trihydrate by drying under reduced pressure at 145—155°C over P2O5 (32). 

Knowing the formula of a compound, Fe203> you can readily calculate the mass percents of its constituent elements. It is convenient to start with one mole of compound (Example 3.4a). The formula of a compound can also be used in a straightforward way to find the mass of an element in a known mass of the compound (Example 3.4b). 

In Situ Derivatization. To demonstrate that a group of alcohols could be derivatized at low alcohol concentration, the following experiment was performed. First, 6 x 10 mole of each of the alcohols used to form derivatives was dissolved in 100 ml of acetonitrile. Then 2 x 10" mole of compound V was added, and the solution was heated at 70°C. This solution was then diluted by taking 1.0 mL of the reaction mixture and diluting to 10 mL with water and acetonitrile, and the diluted solution was analyzed. After 4 h the methanol and ethanol were completely derivatized, but it took 6 h for the n-propanol and n-butanol derivatives to form. 

Conversions of propane and oxygen are defined as moles of propane/oxygen reacted per mole of propane/oxygen fed. The yield of the C3 products was calculated as moles of compound formed per mole of propane... 

The number of moles of each element in a mole of compound is stated in the chemical formula. Hence, the formula can be used to convert the number of moles of the compound to the number of moles of its component elements, and vice versa (Fig. 4-3). 

Ans. The figure is presented as Fig. 4-4. One can convert from mass to moles, moles of component elements, or number of formula units. Additionally, one can convert from number of formula units to moles, to moles of component elements, or to mass. Also from moles of component elements to moles of compound, number of formula units of compound, or mass of compound. Finally, from moles of compound to number of formula units, mass, or number of moles of component elements. 

Method 1 Use the units of formula weight to derive a formula relating grams, moles and formula weight f g grams of compound moles of compound... 

Moles of compound Moles of cations Moles of anions ... 

The molar volume of compounds is the volume that one mole of compound will occupy at a particular temperature. It can be calculated by dividing the atomic weight, AW, of an element by its density. 

Since the carbonate ion, C032, has a formula weight of 60.0 g/mol, then the mass of the metal, Q, in one mole of compound must be... 

Let s = solubility of each compound in moles of compound per liter of solution. 

Let us assume that V moles of solute present initially in a volume V2 of Solvent b Now, this particular sample undergoes extraction with a volume of Solvent a and subsequently y moles of compound are left in V2 at equilibrium. 

Table 5.14 Compilation of thermodynamic data for compounds /3-Mg2Si04, /3-Fe2Si04, y-Mg2Si04 and y-Fe2Si04, after Fei and Saxena (1986). T = 298.15 /, .= bar. Note that each listed value refers to one-half mole of compound (see first column).

Another Zinc Reduction. Prepare or activate the zinc as follows 400 g of mossy zinc is treated with 800 ml of 5% aqueous solution of mercuric chloride for 1 hour. Decant the solution off and use the zinc right away. Add. 834 mole of compound to be reduced to the zinc amalgam, followed by as much HCl acid (.834 mole) diluted in as much water as is required to cover all the zinc. Reflux for 6 hours while adding small portions of dilute HCL acid. Cool, separate the upper, wash free of acid (a few portions of dilute sodium hydroxide), dry and distill to get about a 79% yield of product. 

A) Ca(N03)2 ionizes into three moles of ions per mole of compound... 

B) The formation of hydrogen sulfide from hydrogen gas and sulfur conforms to the definition of both standard enthalpy of reaction and standard enthalpy of formation since the heat change that is measured is for the formation of one mole of compound from the elements in their standard state. In Choice (D), diamond is not the stable aUotrope of carbon—it is graphite. 

Finally, concentration units in soil are a combination of the above with a twist. Soil is a multiphase media, and different concentration units are applied, typically, to each phase. The interstitial space (in between the soil) is filled with water or air in most cases, and the corresponding concentration units for water or air, respectively, would be used. In addition, the concentration of a compound adsorbed to the sediment is normally given either as mass of compound/mass of solid or moles of compound/mass of solid. The mass of solid is one of the few soil parameters that can be determined definitively, so that is what is used. 

Problem 14.58 One mole of compound C(,H,05 reacts with 4 mol of HIO4. The moles of products are 1 HjCO, 1 CH3CH=0, and 3 HCOOH. Supply a possible structure for C(.H,40,. 

The standard free energy of formation of a substance is the standard free energy of reaction per mole of compound when it is formed from its elements in their most stable forms. The sign of AG f tells us whether a compound is stable or unstable with respect to its elements. Standard free energies of formation are used to calculate standard reaction free energies by using Eq. 21. 

E° = E°(cathode) — °(anode). standard enthalpy of combustion AHc° The change of enthalpy per mole of substance when it bums (reacts with oxygen) completely under standard conditions, standard enthalpy of formation AH° The standard reaction enthalpy per mole of compound for the compound s synthesis from its elements in their most stable form at 1 atm and the specified temperature, standard entropy of fusion ASfus° The standard entropy change per mole accompanying fusion (the conversion of a substance from the solid state to the liquid state), standard entropy of vaporization ASvap° The standard entropy change per mole accompanying vaporization (the conversion of a substance from the liquid state to the vapor state). 

Which of the following coin pounds produces the most heat per mole of compound when reacted with oxygen ... 

Coct and Cair are the moles of compound per m3 of octanol and air, poct and Moct are the density (820 kg/m3 at 20°) and molecular weight (130 g/ mol) of octanol, and yoct is the activity coefficient of the solute in octanol. Eliminating P,s from equations (17) and (21) gives... 

The thermodynamic functions of one mole of compound consisting of No identical molecules in standard state are related to the partition function and its derivatives, thus [44] ... 

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