Chemical equations charge balance equation

The reactions that we discuss in this chapter will be represented by nuclear equations. An equation of this type uses nuclear symbols such as those written above in other respects it resembles an ordinary chemical equation. A nuclear equation must be balanced with respect to nuclear charge (atomic number) and nuclear mass (mass number). To see what that means, consider an equation that we will have a lot more to say about later in this chapter ... 

In writing chemical equations and biochemical equations it is important to be careful with names of reactants. Chemical reactions are written in terms of species. In chemical reaction equations, atoms of all elements and electric charges must balance. Biochemical reaction equations are written in terms of reactants, that is in terms of sums of species, H+ is not included as a reactant and electric charges are not shown or balanced. In biochemical reaction equations, atoms of all elements other than hydrogen must balance. The names of the reactants that must be used in making calculations with this data base are given later. 

Determining whether a chemical equation is balanced (see section 0023) requires an additional step for redox reactions because there must be a balance of charge. For example, the equation ... 

X un, J Mg) and in the Fe/(Fe + -I- Mg) ratio (the fe-number). This latter parameter is a useful monitor of the temperature of equilibration and increases with falling temperature (Spear 1993). The chemical data are presented as compositional profiles across individual grains and are shown on graphs of composition v. distance. Most garnets examined in this study are rich in the almandine component, and Fe + was estimated using the charge balance equation of Droop (1987). 

These methods essentially follow the rote procedure outlined above. The important difference is that the mass action, mass balance, and charge balance equations are written in generalized mathematical notation. They can then be applied to any chemical system by specifying the reactions and species of interest. The approach we outline here is described in detail by Crerar (1975). However, we include a change in the mass action equations which was not in the original paper this improves the speed of the method and its chances of success with very complex systems. Consider an bitrary system of c components containing N chemical species. Equilibrium constants are known for M independent reactions relating some or all of these species. 

In all of these oxide phases it is possible that departures from the simple stoichiometric composition occur dirough variation of the charges of some of the cationic species. Furthermore, if a cation is raised to a higher oxidation state, by the addition of oxygen to tire lattice, a conesponding number of vacant cation sites must be formed to compensate tire structure. Thus in nickel oxide NiO, which at stoichiomen ic composition has only Ni + cations, oxidation leads to Ni + ion formation to counterbalance the addition of extra oxide ions. At the same time vacant sites must be added to the cation lattice to retain dre NaCl sUmcture. This balanced process can be described by a normal chemical equation thus... 

In a balanced equation for a chemical reaction, charge is conserved. 

Because electrons can be neither lost nor created in a chemical reaction, all the electrons lost by the species being oxidized must be transferred to the species being reduced. Because electrons are charged, the total charge of the reactants must be the same as the total charge of the products. Therefore, when balancing the chemical equation for a redox reaction, we have to balance the charges as well as the atoms. 

When balancing the chemical equation for a redox reaction involving ions, the total charge on each side must be balanced. 

Another key requirement of chemical equations (when presented in formulae, see below for consideration of word equations), is that they should be balanced . This is considered further below, and relates to conservations that are expected during chemical processes (of matter, charge, energy). 

The simplest balanced chemical equation for a precipitation reaction is a net ionic equation that has ions as the reactants and a neutral solid as the product. In a precipitation reaction, reactant ions combine to form a neutral ionic solid. One reactant carries positive charge and the other carries negative charge, but the product is electrically neutral. Because electrical charge always is conserved, the total positive charge of the reacting cations... 

After oxidation and reduction half-reactions are balanced, they can be combined to give the balanced chemical equation for the overall redox process. Although electrons are reactants in reduction half-reactions and products in oxidation half-reactions, they must cancel in the overall redox equation. To accomplish this, multiply each half-reaction by an appropriate integer that makes the number of electrons in the reduction half-reaction equal to the number of electrons in the oxidation half-reaction. The entire half-reaction must be multiplied by the integer to maintain charge balance. Example illustrates this procedure. 

Simple chemical systems with several components (HCl, KOH, KCl in hydrogel) were used for modeling mass and charge balances coupled with equations for electric field, transport processes and equilibrium reactions [146]. This served for demonstrating the chemical systems function as electrolyte diodes and transistors, so-called electrolyte-microelectronics . 

A chemical equation describes a chemical reaction in many ways as an empirical formula describes a chemical compound. The equation describes not only which substances react, but the relative number of moles of each undergoing reaction and the relative number of moles of each product formed. Note especially that it is the mole ratios in which the substances react, not how much is present, that the equation describes. In order to show the quantitative relationships, the equation must be balanced. That is, it must have the same number of atoms of each element used up and produced (except for special equations that describe nuclear reactions). The law of conservation of mass is thus obeyed, and also the "law of conservation of atoms. Coefficients are used before the formulas for elements and compounds to tell how many formula units of that substance are involved in the reaction. A coefficient does not imply any chemical bonding between units of the substance it is placed before. The number of atoms involved in each formula unit is multiplied by the coefficient to get the total number of atoms of each element involved. Later, when equations with individual ions are written (Chap. 9), the net charge on each side of the equation, as well as the numbers of atoms of each element, must be the same to have a balanced equation. The absence of a coefficient in a balanced equation implies a coefficient of 1. 

The total number of atoms on one side of the equation must balance the total number of atoms on the other side. This rule is simply an expression of the well-known chemical fact that atoms are neither created nor destroyed during a chemical reaction. Remember that subscripts and superscripts are labels describing charges and sites and are not counted in evaluating the atom balance. 

Step 4 Balance the charges on both sides of the equation by adding the appropriate number of electrons (e ) to whichever side is deficient in negative charges. The charge balancing is accomplished as if the electron is like any chemical species—place the appropriate multiplying coefficient in front of eh... 

Because we are generally able to define the chemistry of an aqueous solution containing n chemical elements by analytical procedures, n equations such as 8.48 and 8.49 exist, relating the bulk concentration of a given element mj to all species actually present in solution. Associated with mass balance equations of this type may be a charge balance equation expressing the overall neutrality of the solution ... 

We can write a chemical equation that does balance for all elements and for charge. For example, when ATP is hydrolyzed at a pH above 8.5 in the absence of Mg24, the chemical reaction is represented by... 

The systematic procedure is to write as many independent algebraic equations as there are unknowns (species) in the problem. The equations are generated by writing all the chemical equilibrium conditions plus two more the balances of charge and of mass. There is only one charge balance in a given system, but there could be several mass balances. 

Chemical equations need to be balanced not only in terms of the number of atoms but also by the charge. In other words, just as there should be the same number of atoms before and after the arrow of an equation, there should be the same charge. Take this into account to balance the following chemical equation ... 

Perform exercise 69 before attempting to balance both the atoms and charges of the following chemical equation ... 

Nevertheless, the chemical potentials of SE s are frequently used instead of the chemical potentials of (independent) components of a crystalline system. Obviously, a crystal with its given crystal lattice structure is composed of SE s. They are characterized much more specifically than the crystal s chemical components, namely with regard to lattice site and electrical charge. The introduction of these two additional reference structures leads to additional balanced equations or constraints (beside the mass balances) and, therefore, SE s are not independent species in the sense of chemical thermodynamics, as are, for example, ( - 1) chemical components in an n-component system. 

Note how the nuclear equation for the radioactive decay of uranium-238 is written. The equation is not balanced in the usual chemical sense because the kinds of nuclei are not the same on both sides of the arrow. Instead, a nuclear equation is balanced when the sums of the nucleons are the same on both sides of the equation and when the sums of the charges on the nuclei and any elementary particles (protons, neutrons, and electrons) are the same on both sides. In the decay of 2 U to give He and 2 oTh, for example, there are 238 nucleons and 92 nuclear charges on both sides of the nuclear equation. 

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