Balancing a Chemical Equation

We can now show the process of how to balance a chemical equation for the reaction of the alkane methane, CH4, with oxygen, which produces carbon dioxide and water. This is the reaction that occurs in the flame of a laboratory burner or a gas cooktop as shown in Sample Problem 8.2. 

Count the atoms of each element in the reactants and products. 

Write a balanced chemical equation for the combustion of methane, CH4, using the following unbalanced equation  

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It is easiest to balance a chemical equation one element at a time, starting with the elements that appear in only one substance on each side. Notice that all of the carbon atoms in propane end up in carbon dioxide molecules, and all of propane s hydrogen atoms appear in water molecules. This feature allows us to balance carbon and hydrogen easily. 

C04-0041. Several examples of chemical reasoning are introduced in this chapter. Write out the reasoning steps that you will follow in (a) balancing a chemical equation (b) identifying the limiting reactant (c) determining whether a precipitate forms and (d) computing a reaction yield. 

To balance a chemical equation, the chemical formulas for the reactants are first written on the left-hand side of the equation. For example, in the reaction between hydrochloric acid and sodium hydroxide, the chemical formulas are HCl and NaOH, respectively. Remember that if an acid starts with the prefix hydro-, it is a binary acid. That means that hydrochloric acid is made up of only two... 

Before you can balance a chemical equation, you have to know the formulas for all the reactants and products. If the names are given for these substances, you have to know how to write formulas from the names (Chap. 6). If reactants only are given, you have to know how to predict the products from the reactants. This latter topic is the subject of this section. 

The Law of Conservation of Matter provides the basis for balancing a chemical equation. It states that matter is neither created nor destroyed during an ordinary chemical reaction. Therefore, a balanced chemical equation must always contain the same number of each kind of atom on both sides of the equation. 

In fact, you can use oxidation numbers to balance a chemical equation by a new method. The oxidation number method is a method of balancing redox equations by ensuring that the total increase in the oxidation numbers of the oxidized element(s) equals the total decrease in the oxidation numbers of the reduced element(s). 

All reactions must satisfy ijiass conservation. The reaction A B must be an isomerization reaction because the molecular weights of A and B must be identical. Also, one should add to these relations the requirements that the number of atoms of each element must be conserved, but this is usually intuitively obvious for most reaction systems. We do this whenever we balance a chemical equation. 

Why is it important never to change a subscript in a chemical formula when balancing a chemical equation ... 

Balancing a chemical equation involves finding out how many formula units of each different substance take part in the reaction. A formula unit, as the name implies, is one unit—whether atom, ion, or molecule—corresponding to a given formula. One formula unit of NaCl, for example, is one Na + ion and one Cl ion one formula unit of MgBr2 is one Mg2 + ion and two Br ions and one formula unit of H20 is one H20 molecule. 

In this article, R denotes an organic radical such as Me, Et, Pr, or Ph. X is used to designate halides and pseudohalides, whereas Y is employed to represent a substituent that may be either X or R. For simplicity in some of the structural drawings, M is used to denote a transition metal with its associated ligands. The open arrow (=>) is used when it is not desirable or possible to completely balance a chemical equation. In addition to those... 

You cannot balance an equation by changing any of the chemical formulas. The only way to balance a chemical equation is to put the appropriate numerical coefficient in front of each compound or element in the equation. 

Explain how balancing a chemical equation satisfies the law of conservation of mass. 

Balancing a chemical equation requires an understanding of the Law of Conservation of Mass, which says that mass cannot be created or destroyed. The amount of mass in the reactants will be the amount of mass in the products. The credit for this discovery is given to Antoine Lavoisier, who took very careful measurements of the quantities of chemicals and equipment that he used. Conservation of mass also holds true when balancing equations. The number of atoms of each element in the reactants will be equal to the number of atoms of each element in the products. A useful mnemonic device for conservation of mass is What goes in, must come out. ... 

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... 

An unbalanced chemical equation is of limited use. Whenever you see an equation, you should ask yourself whether it is balanced. The principle that lies at the heart of the balancing process is that atoms are conserved in a chemical reaction. The same number of each type of atom must be found among the reactants and products. Also, remember that the identities of the reactants and products of a reaction are determined by experimental observation. For example, when liquid ethanol is burned in the presence of sufficient oxygen gas, the products will always be carbon dioxide and water. When the equation for this reaction is balanced, the identities of the reactants and products must not be changed. The formulas of the compounds must never be changed when balancing a chemical equation. That is, the subscripts in a formula cannot be changed, nor can atoms be added or subtracted from a formula. 

In balancing a chemical equation, why can you change coefficients, but not subscripts ... 

Least Common Multiples When writing chemical formulas or balancing a chemical equation, being able to identify the least common multiple of a set of numbers can often help. Your graphing calculator has a least common multiple function that can compare two numbers. On a TI-83 Plus or similar graphing calculator, press MATH >- 8. The screen should read lcm(. Next, enter one number and then a comma followed by the other number and a closing parenthesis. Press ENTER, and the calculator will show the least common multiple of the pair you entered. 

When balancing a chemical equation, can you adjust the number that is subscripted to a substance formula Explain your answer. 

What can we do to balance a chemical equation All we are allowed to do is add coefficients in front of the chemical formulas to achieve the proper balance. The correct way to balance the equation from Example 2 is ... 

Before I leave you with the practice problems, let me give you one last important piece of information. If you ever find that all of the coefficients that you used to balance an equation are reducible by the same number, you must reduce your coefficients. For example, let s suppose you balanced a chemical equation and came up with this result ... 

The equation shows an atom of potassium transforming into an atom of calcium and an additional particle that we haven t learned yet. When we discussed creating an atomic tally to balance a chemical equation in Lesson 6-1, we said that you must have the same number of atoms of each... 

Review the following concepts before studying this chapter. Chapter 2 structure of the nucleus Chapter 6 how to balance a chemical equation Chapter 8 the actinides Chapter 19 DNA structure... 

Once we have identified all the reactants and products and have written the correct formulas for them, we assemble them in the conventional sequence—reactants on the left separated by an arrow from products on the right. The equation written at this point is likely to be unbalanced that is, the number of each type of atom on one side of the arrow differs from the number on the other side. In general, we can balance a chemical equation by the following steps ... 

Many equations are balanced by trial and error. After the identity of the products and reactants, the physical state, and the reaction conditions are known, the following steps provide a method for correctly balancing a chemical equation ... 

The identities (formulas) of the compounds must never be changed in balancing a chemical equation. 

Because atoms are just rearranged (not created or destroyed) in a chemical reaction, we must always balance a chemical equation. 

O Why is it important to balance a chemical equation before proceeding to answer questions about it ... 

Why must you first balance a chemical equation before you can write the equilibrium expression ... 

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