Water formula unit

This equation means that, in the presence of water, formula units of MgCl2 completely dissociate into the separate ions. Therefore, the best representation of MgCl2(aq) is Mg2+(aq) -I- 2 Cr(aq). 

Ionic compounds are named by starting with the name of the cation (with its oxidation number if more than one charge is possible), followed by the name of the anion hydrates are named by adding the word hydrate, preceded by a Greek prefix indicating the number of water molecules in the formula unit. 

E.9 Epsom salts consist of magnesium sulfate heptahydrate. Write its formula, (a) How many atoms of oxygen are in 5.15 g of Epsom salts (b) How many formula units of the compound are present in 5.15 g (c) How many moles of water molecules are in 5.15 g of Epsom salts ... 

E.22 (a) How many CaH2 formula units are present in 5.294 g of CaH2 (b) Determine the mass of 6.25 X 1024 formula units of NaBF4, sodium tetrafluoroborate. (c) Calculate the amount (in moles) of 9.54 X 1021 formula units of Cel3, cerium(III) iodide, a bright yellow, water-soluble solid. 

When any 2 atoms of sodium react with 2 molecules of water, they produce 2 formula units of NaOH and one molecule of hydrogen. 

STRATEGY When Ba(OH)2 dissolves in water, it provides OH ions most hydroxides of Groups 1 and 2 can be treated as fully dissociated in solution. Decide from the chemical formula how many OH ions are provided by each formula unit and calculate the concentrations of these ions in the solution. To find the concentration of H,Oj ions, use the water autoprotolysis constant Kw = [H,0 1 [OH ]. 

The concentration of AgT ions, and hence the solubility of AgCI formula units, is 1.6 X 10 6 mol-L 1, which is about 10 times less than the solubility of AgCI in pure water. 

Another way to calculate this molar mass is by working with the individual components of the formula. Each formula unit of the compound contains one iron(II) cation, two nitrate anions, and six waters of hydration ... 

Begin by finding the chemical formula from the name, nickel(II) chloride hexahydrate. Chloride ion carries -1 charge, and the (II) indicates that nickel is a +2 cation. Electrical neutrality requires two chlorides for every nickel. The name also tells us that the salt contains six water molecules for each unit of nickel(II) chloride. Thus, each formula unit of the salt contains one cation, two Cl anions,... 

The equilibrium concentration of Pb ions is stated to be 1.35 X 10 M, but the equilibrium concentration of iodide ions is not stated [Pb2- ],q = 1.35 X iO M[r]g(j — The equilibrium concentration of I is determined by stoichiometric analysis. Initially, the system contains only pure water and solid lead(II) iodide. Enough Pbl2 dissolves to make [Pb ]gq = 1.35 X 10 M. One formula unit of Pbl2 contains one Pb cation and two I" anions. Thus, twice as many iodide ions as lead ions enter the solution. The concentration of I at equilibrium is double that of Pb cations [r],q-2[Pb ],q-2.70 X lO M Substitute the values of the concentrations at equilibrium into the equilibrium expression and calculate the result ... 

It is safer in many instances to assume the solvated proton has the formula unit [H(H20)4]+, with four water molecules arranged tetrahedrally around a central proton, the proton being stabilized by a lone pair from each oxygen atom. 

Characterization of Interlayer Water. X-ray diffraction studies of the 10A hydrate show no hkl reflections indicating a lack of regularity in the stacking of the kaolin layers. In addition to the 10A hydrate, two other less hydrated kaolinites were synthesized. Both have one molecule of water for each formula unit in contrast to the 10A hydrate which has two. These less hydrated clays consequently have smaller d(001) spacings of 8.4 and 8.6 A. The synthesis conditions for these two hydrates are described in (22.). By studying the interlayer water in the 8.4 and 8.6A hydrates, it was possible to formulate a model of the water in the more complicated 10A hydrate. 

C—The general formula, C H2b, means that 1 mol of H20 will form per mole of empirical formula unit, regardless of the value of n. The moles of water formed is the mass of the alkene divided by the empirical formula mass. 

One of the most important electrolytic processes is the extraction of aluminum from an ore called bauxite. This ore is mainly composed of hydrated aluminum oxide, AI2O3 XH2O. (The x in the formula indicates that the number of water molecules per formula unit is variable.) In industry, the scale of production of metals is huge. The electrolytic production of aluminum is over two million tonnes per year in Canada alone. As you know from Faraday s law, the amount of a metal produced by electrolysis is directly proportional to the quantity of electricity used. Therefore, the industrial extraction of aluminum and other metals by electrolysis requires vast quantities of electricity. The availability and cost of electricity greatly influence the location of industrial plants. 

Iron(ni) hydroxide readily breaks down to form hydrated iron(III) oxide, Fe203 XH2O, more commonly known as rust. As noted earlier, the x signifies a variable number of water molecules per formula unit. 

Guenee et al. [169] synthesized by ingot metallurgy ternary intermetallic compounds LaNi Mg and NdNi Mg having the cubic MgCu Sn crystal structure. They can absorb reversibly up to four hydrogen atoms per formula unit at 7-8 bar and 50°C. The hydrides are stable at room temperature but desorb quite rapidly at 80°C in vacuum. In air, they decompose by catalytic water formation. 

The sodium carbonate is a strong electrolyte and each formula unit dissociates completely to form 3 ions when placed in water. 

What is the molar mass of water (formula mass = 18 atomic mass units) ... 

K2La2Ti3Oio is a typical oxide in the Ruddlesden-Popper series exhibiting interlayer reactivity44) It forms a hydrate with about 1-2 H20 molecules per formula unit under ambient conditions.44,74) Fig. 16.9 shows schematic structures of anhydrous and hydrated oxides. Variation of the number of waters of hydration with humidity and exposure time has been reported for the analogous compound K2Nd2Ti3O10.70) A band gap of 3.5 eV has been estimated for K2La2Ti3Oi0 from reflectance measurements.102)... 

G.15 A chemist prepared an aqueous solution by mixing 2.50 g of ammonium phosphate trihydrate, (NH4)3P04-3H20 and 1.50 g of potassium phosphate, K3P04, with 500 g of water, (a) Determine the number of moles of formula units of each compound that was measured, (b) How many moles of P043- are present in solution (c) Calculate the mass of phosphate ions present in the solution, (d) What is the total mass of the water present in the solution ... 

STRATEGY The solution contains N02 , a base, so we expect the pH to be i higher than that of nitrous acid alone. The K+ ion has no protons to donate j and cannot accept a proton, so it has no measurable effect on the pH of the ] solution. Identify the proton transfer equilibrium and use it to find the pH by means of an equilibrium table. Consider the initial molarity of HN02 (before reaction with water) to be 0.500 mol-L1. Because nitrite ions have also been added to the solution, set their initial molarity equal to the molar-5 ity of added salt (each KN02 formula unit supplies one N02 anion). Then proceed as described in Toolbox 10.1. Because the concentrations of the 1 added ions are much higher than 10-7 mol-L 1, we assume that we can S ignore the contribution to the pH from the autoprotolysis of water. 

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