Molecular and Ionic Equations

Lil(i) and CH30H(/) are each introduced into a separate beaker containing water. Using the drawings shown here, label each beaker with the appropriate compound and indicate whether you would expect each substance to be a strong electrolyte, weak electrolyte, or nonelectrolyte. 

We use chemical equations to help us describe chemical reactions. For a reaction involving ions, we have a choice of chemical equations, depending on the kind of information we want to convey. We can represent such a reaction by a molecular equation, a complete ionic equation, or a net ionic equation. 

To illustrate these different kinds of equations, consider the preparation of precipitated calcium carbonate, CaC03. This white, fine powdery compound is used as a paper filler to brighten and retain ink, as an antacid (as in the trade-named Turns), and as a mild abrasive in toothpastes. One way to prepare this compound is to react calcium hydroxide, Ca(OH)2, with sodium carbonate, Na2C03. Let us look at the different ways to write the equation for this reaction. 

You could write the equation for this reaction as follows  

We call this a molecular equation, which is a chemical equation in which the reactants and products are written as if they were molecular substances, even though they may actually exist in solution as ions. The molecular equation is useful because it is 

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Molecular and Ionic Equations Types of Chemical Reactions... 

Write balanced molecular and ionic equations showing the following reactions silver nitrate and sodium chloride solutions to form silver chloride and sodium nitrate hydrochloric acid and sodium hydroxide to form sodium chloride and water zinc and copper(ii) sulfate solution to form zinc sulfate and copper sodium carbonate and hydrochloric acid to form sodium chloride, water and carbon dioxide. 

Two activity coefficient models have been developed for vapor-liquid equilibrium of electrolyte systems. The first model is an extension of the Pitzer equation and is applicable to aqueous electrolyte systems containing any number of molecular and ionic solutes. The validity of the model has been shown by data correlation studies on three aqueous electrolyte systems of industrial interest. The second model is based on the local composition concept and is designed to be applicable to all kinds of electrolyte systems. Preliminary data correlation results on many binary and ternary electrolyte systems suggest the validity of the local composition model. 

Reactions of cations in aqueous solution with sodium hydroxide - Al3+, Fe2+, Fe3+, Cu2+, Ca2+, Zn2, Cr3+,. An excess of sodium hydroxide solution is added slowly to a small volume of the solution containing the cation. This is an exercise in observation, organisational and recording skills and in the ability to write chemical equations - word, molecular and ionic. 

Here, Ms and Ms,ads are the electrochemical potentials of S in the bulk solution and in the adsorbed state. Let us apply the Gibbs adsorption equation to the interphase between a pure metal M and an aqueous solution containing molecular and ionic species denoted by the subscript j, in addition to water w and the species S. Choosing the neutral metal atoms M and the electrons e in excess with respect to metal atoms as the constituents of the metal phase, we may formally write ... 

When a drug is a weak acid or a weak base, we find that its lipid solubility is greatly affected by the pH of its environment and by its degree of dissociation, expressed as pKa. The fraction of the total drug concentration that is in the molecular and ionic forms is indicated by the dissociation constant Ka. Equations 1.2 and 1.3 illustrate the interaction of weak acids and weak bases with water, which results in dissociation. A and B represent acids and bases, respectively. 

The Gibbs equation Eq, (17,1-1)] forms the basis of adsoiptive bubble separations of molecular and ionic species ... 

The sum of molecular and ionic form concentrations in the saturated solution, 2sMeo> is obtained as the main result of such investigations, this magnitude may be expressed by the following equation ... 

The cooling rates of trans-stilbene have been measured in a number of molecular liquids as well as in ionic liquids tFig. 8.111 [8]. The results show a marked contrast between the molecular and ionic liquids, in molecular liquids, including alkanes (heptane, hexane, octane, nonane, decane), alcohols (methanol, ethanol, ethylene glycol) and others (chloroform, toluene), a clear linear relation is observed between the cooling rate k and the bulk thermal diffusivity k (right-hand box in Fig. 8.111. Thermal diffusivity k is defined in the diffusion equation of heat. Equation 8.1 ... 

Electronic structure methods are aimed at solving the Schrodinger equation for a single or a few molecules, infinitely removed from all other molecules. Physically this corresponds to the situation occurring in the gas phase under low pressure (vacuum). Experimentally, however, the majority of chemical reactions are carried out in solution. Biologically relevant processes also occur in solution, aqueous systems with rather specific pH and ionic conditions. Most reactions are both qualitatively and quantitatively different under gas and solution phase conditions, especially those involving ions or polar species. Molecular properties are also sensitive to the environment. 

The diffusion current Id depends upon several factors, such as temperature, the viscosity of the medium, the composition of the base electrolyte, the molecular or ionic state of the electro-active species, the dimensions of the capillary, and the pressure on the dropping mercury. The temperature coefficient is about 1.5-2 per cent °C 1 precise measurements of the diffusion current require temperature control to about 0.2 °C, which is generally achieved by immersing the cell in a water thermostat (preferably at 25 °C). A metal ion complex usually yields a different diffusion current from the simple (hydrated) metal ion. The drop time t depends largely upon the pressure on the dropping mercury and to a smaller extent upon the interfacial tension at the mercury-solution interface the latter is dependent upon the potential of the electrode. Fortunately t appears only as the sixth root in the Ilkovib equation, so that variation in this quantity will have a relatively small effect upon the diffusion current. The product m2/3 t1/6 is important because it permits results with different capillaries under otherwise identical conditions to be compared the ratio of the diffusion currents is simply the ratio of the m2/3 r1/6 values. 

Returning to the molecular force concept, in any particular distribution system it is rare that only one type of interaction is present and if this occurs, it will certainly be dispersive in nature. Polar interactions are always accompanied by dispersive interactions and ionic interactions will, in all probability, be accompanied by both polar and dispersive interactions. However, as shown by equation (11), it is not merely the magnitude of the interacting forces between the solute and the stationary phase that will control the extent of retention, but also the amount of stationary phase present in the system and its accessibility to the solutes. This leads to the next method of retention control, and that is the volume of stationary phase available to the solute. 

In nitric acid, three oxygen atoms are bonded directly to a nitrogen atom, and a hydrogen is bonded to one of the oxygens. Write the net ionic equation and draw a molecular picture that illustrates the reaction between nitric acid and water. 

Finally, it must be recalled that the transport properties of any material are strongly dependent on the molecular or ionic interactions, and that the dynamics of each entity are narrowly correlated with the neighboring particles. This is the main reason why the theoretical treatment of these processes often shows similarities with models used for thermodynamic properties. The most classical example is the treatment of dilute electrolyte solutions by the Debye-Hiickel equation for thermodynamics and by the Debye-Onsager equation for conductivity. 

Ionic and molecular species present in chemical systems net ionic equations... 

Sections III. 1-III. 3 have described some basic discrete molecular and continuum treatments of solute-solvent interactions. There are many variants and refinements of these that have not been discussed, such as the use of effective dielectric constants66 or the implementation of dielectric screening.155 156 For ionic solutions, it is sometimes preferred to find the reaction field potential via the Poisson-Boltzmann rather than the Poisson equation,132 157 since the effects of the other ions can readily be incorporated into the former.158... 

Be able to write the reactants and products in their ionic form, as in the ionic equation example above. Be sure, however, that you do not try to break apart molecular compounds such as most organic compounds, or insoluble species. 

In the molecular equation, the reactants and products are shown in their undissociated/unionized form the ionic equation shows the strong electrolytes in the form of ions the net ionic equation drops out all spectator ions and shows only those species that are undergoing chemical change. 

In basic solution, Mn04 oxidizes glycerol to carbonate. The net ionic equation and formal molecular reaction are ... 

Calculate the normality of the prepared acid from the data obtained. Write the molecular and net ionic equations of the neutralization reaction. 

Pour 5 ml of a 1 W hydrochloric acid solution into a test tube and throw a small piece of zinc into it. When the evolution of hydrogen becomes quite vigorous, add 1-2 g of sodium acetate. Explain the change in the rate of hydrogen evolution. Write the molecular and net ionic equations of the chemical reaction of hydrochloric acid with sodium acetate. Does the activity of acetic acid decrease when dry sodium acetate is added to its solution ... 

Write the equations of the hydrolysis reactions of the studied salts in the molecular and net ionic forms. Define the degree of hydrolysis and the hydrolysis constant. 

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