Chemical equations rules

This rule allows you to find AH corresponding to any desired amount of reactant or product. To do this, you follow the conversion-factor approach used in Chapter 3 with ordinary chemical equations. Consider, for example,... 

The equilibrium constant expression for the dissolving of SrCr04 can be written following the rules in Chapters 12 and 13. In particular, the solid does not appear in the expression the concentration of each ion is raised to a power equal to its coefficient in the chemical equation. 

Clausius-Clapeyron equation An equation expressing the temperature dependence of vapor pressure ln(P2/Pi) = AHvapCl/Tj - 1/T2)/R, 230,303-305 Claussen, Walter, 66 Cobalt, 410-411 Cobalt (II) chloride, 66 Coefficient A number preceding a formula in a chemical equation, 61 Coefficient rule Rule which states that when the coefficients of a chemical equation are multiplied by a number n, the equilibrium constant is raised to the nth power, 327... 

Rule To find any proposed heat of reaction write down the chemical equations of the component reactions so that each symbol appears equally often on both sides of the sign of equality. If the heats of reaction (with proper signs) have been inserted, the unknown heat of reaction being denoted by x then the latter... 

If we compare (3) with the chemical equation of the reaction we arrive at the simple rule that the concentrations in the equilibrium state at a. given te i.perature and pressure must have... 

Because equilibrium constants must be raised to a power when a chemical equation is multiplied by a factor, and therefore change in magnitude, these rules are only general guidelines. 

The oxidation state of an element in a compound is an indication of how many electrons each atom of that element has lost (positive oxidation state) or gained (negative). Since oxidation state is determined by a set of rules, rather than by experiment, its connection to the number of electrons actually transferred is rather tenuous. It is used in naming compounds and balancing some chemical equations. 

In this case, as in all others, a calculation should be made at the conclusion of the experiment of the percentage of the theoretical yield which has been obtained, keeping in mind the following considerations. According to the chemical equation one mole of alcohol (46) should be used for one mole of potassium bromide (119). Actually, however, in the case of organic reactions, which as a rule do not proceed quantitatively, one of the components is used in excess, in keeping with the law of mass action (pp. 142,143), and its choice is often determined by economic considerations. Thus, for example, 1 kg. of potassium bromide costs about 6s., and 1 kg. of duty-free alcohol, Is. 2d. The price of a mole of KBr (119 x 6s.) is therefore to that of a mole of alcohol (95 per cent) (46 x Is. 2d.) approximately as 14 1. From the economic standpoint it is therefore advisable to use the cheaper alcohol in excess in order that as much as possible of the dearer bromine compound may be con-... 

Other factors also provided a degree of added stability to unit processes. In particular, the analytical "taxonomy" offered by Shreve in 1937 not only played an important role in the classroom, it also provided a useful guide for designing a chemical reactor whenever a series of approximations had to replace the equations ruling a well-defined model - and that was most of the time (49). 

It must be found by experiment. Elementary reactions are the exception to this rule. For an elementary reaction, the exponents in the rate law equation are the same as the stoichiometric coefficients for each reactant in the chemical equation. Table 6.3 shows how rate laws correspond to elementary reactions. 

Any reaction in Eqs. (1) may be written as a conventional chemical equation by setting it equal to zero and transposing the negative terms to the other side of the equation. This notation has been discussed by Aris (14). Chemical equality, denoted by the symbol has been shown by Sellers (15) to be a group equivalence, thus satisfying ordinary rules of mathematical equality. Except when specific reservations are stated, every reaction is assumed to be reversible, that is, to be capable of any real rate of advancement, positive or negative. 

Mechanism is a technical term, referring to a relatively detailed, microscopic description of a chemical transformation, which, nevertheless, slill falls far short of a complete dynamical description at the atomic level. A mechanism for a reaction is sufficient to predict the macroscopic rale law til the reaction This deductive process is valid only in one direction, i.e,. an unlimited number of mechanisms are consistent with any measured rule law. A successful kinetic study postulates a mechanism, derives the rate law. and demonstrates that the rale law is sufliciem to explain experimental data over some range of conditions, New data may be discovered later that prove inconsistent with the assumed tuic law and lequite that a new mechanism he postulated. Mechanisms stale, in particular, what molecules actually react in an elementary step and what products these produce. An overall chemical equation tnuy involve a variety of intermediates, and the mechanism specifies those intermediates. 

The rules for writing the equilibrium constant expression apply to reactions in solution as well as to gas-phase reactions. Put the concentrations of the products in the numerator and the concentrations of the reactants in the denominator. No exponents are needed because all the coefficients in the balanced chemical equation equal unity. 

Notice that the atoms have been reorganized. Bonds have been broken and new ones formed. Remember that in a chemical reaction atoms are neither created nor destroyed. All atoms present in the reactants must be accounted for among the products. In other words, there must be the same number of each type of atom on the product side and on the reactant side of the arrow. Making sure that this rule is followed is called balancing a chemical equation for a reaction. The equation (shown above) for the reaction between CH4 and 02 is not balanced. As we will see in the next section, the equation can be balanced to produce... 

A good rule to follow is to lurite the chemical equation to correspond as closely as possible to the actual reaction, showing the molecules or ions which actually react and are formed. 

Equation (4) illustrates the application of the phase rule to equilibria between solids and solutions. Thus the number of variable concentrations in the equilibrium equation is exactly equal to the degrees of freedom / of the system, namely, the total number n of the molecular types taking part in the reaction less the number B of the substances present in the solid phase (f=n—B) n is also the number of the independent components of the system, which is equal to the total number of molecular types present (n-f sol vent), less the number of the chemical equations (1). The number of phases is P = B+2 (solution and vapour). Hence... 

Chemical equations can be manipulated using rules of algebra to get a desired equation. When equations are added or subtracted, enthalpy changes must be added or subtracted. And when equations are multiplied by a constant, the enthalpy changes must also be multiplied by that constant. For example, the enthalpy of the formation of CO, when CO2 and solid carbon are reactants, is found using the equations below. 

The bond orders we are considering are the ones defined in terms of the classical structural formulae, which can be related to the numbers of bonding and anti-bonding electrons. They are not the bond orders derived from molecular orbital numerical calculations as given by Eq. (9.45). An additional uniformity involving such bond orders and chemical equations can be found, directly related to the octet rule. For example, by considering... 

These chemical equations show how atoms share electrons to become stable. As can be seen by the Lewis structures (left side) for the molecules, after a reaction, all atoms in the molecules are stable according to the octet rule. 

Experiments show that as long as some liquid water is in the container, the pressure of water vapor at 25°C is 0.03126 atm. The position of this equilibrium is not affected by the amount of liquid water present, and therefore liquid water should not appear in the mass action law. Recall that for a gas or solute, a ratio of pressures or concentrations appears in the law of mass action. This ratio is equal to 1 when the gas or solute is in its reference state (1 atm or 1 M). For a pure liquid appearing in an equilibrium chemical equation, the convention is to take that pure liquid as the reference state, so the liquid water contributes only a factor of 1 to the equilibrium expression and can thus be entirely omitted. We postpone justification of this rule to Section 14.3. 

You can see that any number of chemical equations can be treated by algebraic methods, and the corresponding standard heats of reaction can be added or subtracted in the same fashion as are the equations. By carefully following these rules of procedure, you will avoid most of the common errors in thermochemical calculations. 

Such chemical equations must obey certain rules ... 

The rules for balancing nuclear equtions are different from the rules for balancing ordinary chemical equations. 

Injiecidmg the number of components in any given system, not only must the constituents chosen be,jcnp bde -rQFiiid4ap ft4 tiuMi, but a further restriction is imposed, and we obtain the following rule As the components of a system there are to be chosen the smallest NUMBER of independently variable constituents by means of which the composition of each phase participating in the state of equilibrium can be expressed in the form of a chemical equation. 

For nonmetals there is no single rule. Carbon, for example, exists as an extensive three-dimensional network of atoms, and so we use its empirical formula (C) to represent elemental carbon in chemical eqnations. Bnt hydrogen, nitrogen, oxygen, and the halogens exist as diatomic molecules, and so we use their molecular formulas (H2, N2, O2, F2, CI2, Br2,12) in equations. The stable form of phosphorus is molecular (P4), and so we use P4. For sulfur chemists often nse the empirical formula (S) in chemical equations, rather than Sg which is the stable form. Thus, instead of writing the equation for the combnstion of sulfur as... 

Using the solubility rules provided in the table above, complete the following chemical equations. Indicate whether a precipitate forms or not. Identify the precipitate. If no reaction occurs, write NR. 

In order to compare the response of the sensor interface with the ORN output spiking rate, they have been considered sensors with a resistance time evolution in presence of a step of chemical stimulus ruled by the equation ... 

Furthermore, the program has to interpret chemical formulas. For example if the student types "NH3OH" for the formula of ammonium hydroxide he should be told that the hydrogen is incorrect and not that he has misspelled a word. The routine F.QTJUDG was written to interpret any chemical equation. The routine controls the balancing of mass and charge in chemical equations and checks other rules for writing chemical equations, e.g. 

In lesson C the student must know the definition of molarity and moles, the quantitative relationship of a chemical equation to determine quantities of reactants and products for reactions. Lesson D has the following objectives Assignment of oxidation numbers to elements according to a set of rules balancing oxidation-reduction equations by the half-reaction method and identification of oxidizing and reducing agents. 

Chemical equations are devices for accounting . In the course of chemical reactions, no atoms must be lost or gained. Chemical equations should therefore be balanced to ensure that this rule holds. Typical balanced equations are ... 

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