Unbalanced chemical equations

An unbalanced chemical equation shows the reactants and products without the correct coefficients. For example, the equation... 

The observant reader will notice that some of the equations in this book are not balanced. Although unbalanced chemical equations can be distracting, there are times when trying to balance them is even more distracting. Chemical equations involving polymers certainly can be balanced, but doing so often leads to confusion. For example, consider this simple reaction from Chapter 2 indicating the formation of nylon-6 ... 

Consider the unbalanced chemical equation corresponding to the formation of solid lead(II) chromate, PbCr04 ... 

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. 

Most chemical equations can be balanced by inspection—that is, by trial and error. It is always best to start with the most complicated molecules (those containing the greatest number of atoms). For example, consider the reaction of ethanol with oxygen, given by the unbalanced equation... 

Write an unbalanced chemical equation for each of the following. 

Not all chemical equations are balanced so easily. For example, silver tarnishes, as in Figure 5, when it reacts with sulfur compounds in the air, such as hydrogen sulfide. The following unbalanced equation shows what happens when silver tarnishes. 

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 ... 

As we saw in the previous section, an unbalanced chemical equation is not an accurate representation of the reaction that occurs. Whenever you see an equation for a reaction, you should ask yourself whether it is balanced. 

Write the formulas of the reactants and products to give the unbalanced chemical equation. 

If calcium carbonafe is heafed strongly, carbon dioxide gas is driven off, leaving a residue of calcium oxide. Wrife fhe unbalanced chemical equation for fhis process. 

Liquefied propane gas is offen used for cooking in rural areas away from nafural gas lines. Propane (CgHg) burns in oxygen gas, producing carbon dioxide gas, wafer vapor, and heat. Write the unbalanced chemical equation for this process. 

If a sample of pure hydrogen gas is ignif ed very carefully, the hydrogen burns gently, combining with the oxygen gas of the air to form wafer vapor. Write the unbalanced chemical equation for this reaction. 

Methanol (CH3OH, wood alcohol) is an important industrial chemical. Methanol may be synthesized from carbon monoxide gas and hydrogen gas under certain conditions of temperature and pressure. Write the unbalanced chemical equation for this process. 

Calcium metal is moderately reactive. If pieces of calcium are added to water, the metal begins to bubble as hydrogen gas is formed. The water begins to turn cloudy as solid calcium hydroxide begins to form. Write the unbalanced chemical equation... 

Magnesium hydroxide has been used for many years as an antacid ("milk of magnesia") because it reacts with the hydrochloric acid in the stomach, producing magnesium chloride and water. Write the unbalanced chemical equation for fhis process. 

Nifrous oxide gas (systemafic name dinifrogen monoxide) is used by some denfisfs as an anes-fhefic. Nifrous oxide (and wafer vapor) can be produced in small amounfs in fhe laborafory by careful heating of ammonium nifrafe. Write the unbalanced chemical equation for fhis reaction. 

Acetylene gas (C2H2) is often used by plumbers, welders, and glass blowers because it burns in oxygen with an intensely hot flame. The products of the combustion of acetylene are carbon dioxide and water vapor. Write the unbalanced chemical equation for this process. 

The Group 2 metals (Ba, Ca, Sr) can be produced in the elemental state by the reaction of their oxides with aluminum metal at high temperatures, also producing solid aluminum oxide. Write the unbalanced chemical equations for the reactions of barium oxide, calcium oxide, and strontium oxide with aluminum. 

Carbon tetrachloride may be prepared by the reaction of natural gas (methane, CH ) and chlorine gas in the presence of ultraviolet light. Write the unbalanced chemical equation for this process. (HCl is also a product.)... 

Ammonium nitrate is used as a "high-nitrogen" fertilizer, despite the fact that it is quite explosive if not handled carefully. Ammonium nitrate can be synthesized by the reaction of ammonia gas and nitric acid. Write the unbalanced chemical equation for this process. 

The principal natural ore of lead is galena, which is primarily lead(ll) sulfide. Lead(ll) sulfide can be converted to lead(ll) oxide and sulfur dioxide gas by heating strongly in air. Write the unbalanced chemical equation for the reaction of lead(ll) sulfide with oxygen gas. 

Silver nitrate is used in "styptic pencils," which help to cauterize small nicks and cuts that occur during shaving. Silver nitrate can be prepared by dissolving metallic silver in concentrated nitric acid, with hydrogen gas being an additional product of the reaction. Write the unbalanced chemical equation for this process. 

Many ships are built with aluminum superstructures to save weight. Aluminum, however, burns in oxygen if there is a sufficiently hot ignition source, which has led to several tragedies at sea. Write the unbalanced chemical equation for the reaction of aluminum with oxygen, producing aluminum oxide as the product. 

Crude gunpowders often contain a mixture of potassium nitrate and charcoal (carbon). When such a mixture is heated until reaction occurs, a solid residue of potassium carbonate is produced. The explosive force of the gunpowder comes from the fact that two gases are also produced (carbon monoxide and nitrogen), which increase in volume with great force and speed. Write the unbalanced chemical equation for the process. 

For each of the following unbalanced chemical equations, calculate how many moles of each product would be produced by the complete conversion of 0.125 mol of the reactant indicated in boldface. State clearly the mole ratio used for fhe conversion. 

For each of the following unbalanced chemical equations, suppose that exactly 50.0 g of each reactant is taken. Determine which reactant is limiting, and calculate what mass of the product in boldface is expected. (Assume that the limiting reactant is completely consumed.)... 

Alkali metal hydroxides are sometimes used to "scrub" excess carbon dioxide from the air in closed spaces (such as submarines and spacecraft). For example, lithium hydroxide reacts with carbon dioxide according to the unbalanced chemical equation... 

I Consider the reaction represented by the following unbalanced chemical equation... 

I Hydrogen gas (H2) and oxygen gas (O2) react to form water vapor according to the following unbalanced chemical equation ... 

Given the following unbalanced chemical equation for the combination reaction of sodium metal and chlorine gas... 

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