A common demonstration in chemistry courses involves adding a tiny speck of manganese(IV) oxide to a concentrated hydrogen peroxide, H2O2, solution. Hydrogen peroxide is unstable, and it decomposes quite spectacularly under these conditions to produce oxygen gas and steam (water vapor). Manganese(IV) oxide is a catalyst for the decomposition of hydrogen peroxide and is not consumed in the reaction. Write the balanced equation for the decomposition reaction of hydrogen peroxide.
> If oxygen molecules, O2, were to react with magnesium atoms, how many electrons would each magnesium atom lose? How many electrons would each oxygen atom gain? How many magnesium atoms would be needed to react with each oxygen molecule? What charges woul
> If atoms of the metal calcium were to react with molecules of the nonmetal fluorine, F2, how many electrons would each calcium atom lose? How many electrons would each fluorine atom gain? How many calcium atoms would be needed to react with one fluorine
> The thermite reaction produces so much energy (heat) that the iron is initially formed as a liquid. 2Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s) Describe the transfer of electrons for both the aluminum and iron.
> Give an example of a simple chemical reaction that involves the transfer of electrons from a metallic element to a nonmetallic element.
> What is an oxidation–reduction reaction? What is transferred during such a reaction?
> When writing the chemical equation for a reaction, how do you indicate that a given reactant is dissolved in water? How do you indicate that a precipitate has formed as a result of the reaction?
> Along with the three strong acids emphasized in the chapter (HCl, HNO3, and H2SO4), hydrobromic acid, HBr, and perchloric acid, HClO4, are also strong acids. Write equations for the dissociation of each of these additional strong acids in water.
> Write balanced equations showing how three of the common strong acids ionize to produce hydrogen ion.
> If electricity of sufficient voltage is passed into a solution of potassium iodide in water, a reaction takes place in which elemental hydrogen gas and elemental iodine are produced, leaving a solution of potassium hydroxide. Write the unbalanced equatio
> What is a salt? Give two balanced chemical equations showing how a salt is formed when an acid reacts with a base.
> If 1000 NaOH units were dissolved in a sample of water, the NaOH would produce Na1 ions and OH2 ions.
> Write the formulas and names of three common strong acids and strong bases.
> The same net ionic process takes place when any strong acid reacts with any strong base. Write the equation for that process.
> What is meant by a strong base? Are the strong bases also strong electrolytes? Explain.
> What is meant by a strong acid? Are the strong acids also strong electrolytes? Explain.
> Another step in the qualitative analysis of cations (see Exercise 28) involves precipitating some of the metal ions as the insoluble sulfides (followed by subsequent treatment of the mixed sulfide precipitate to separate the individual ions). Write balan
> A reaction in aqueous solution that results in the formation of a solid is called a reaction.
> Many plants are poisonous because their stems and leaves contain oxalic acid, H2C2O4, or sodium oxalate, Na2C2O4; when ingested, these substances cause swelling of the respiratory tract and suffocation. A standard analysis for determining the amount of o
> The procedures and principles of qualitative analysis are covered in many introductory chemistry laboratory courses. In qualitative analysis, students learn to analyze mixtures of the common positive and negative ions, separating and confirming the prese
> Liquid hydrazine, N2H4, has been used as a fuel for rockets. When the rocket is to be launched, a catalyst causes the liquid hydrazine to decompose quickly into elemental nitrogen and hydrogen gases. The rapid expansion of the product gases and the heat
> Many chromate (CrO42-) salts are insoluble, and most have brilliant colors that have led to their being used as pigments. Write balanced net ionic equations for the reactions of Cu2+, Co3+, Ba2+, and Fe3+ with chromate ion.
> Write the balanced molecular, complete ionic, and net ionic equations for the reaction between nickel(II) chloride and sodium sulfide.
> Which of the following most accurately describes a spectator ion? a. An ion that is used up in a chemical reaction; it is limiting. b. An ion that participates in a chemical reaction but is always present in excess c. An ion that becomes part of the p
> A solution of zinc nitrate is mixed with a solution of potassium hydroxide. A precipitate forms. Complete and balance the equation for this reaction, including the phases of each reactant and product.
> What is a “driving force”? What are some of the driving forces discussed in this section that tend to make reactions likely to occur? Can you think of any other possible driving forces?
> On the basis of the general solubility rules given in Table 7.1, for each of the following compounds, explain why the compound would not be expected to be appreciably soluble in water. Indicate which of the solubility rules covers each substance’s partic
> On the basis of the general solubility rules given in Table 7.1, for each of the following compounds, explain why the compound would be expected to be appreciably soluble in water. Indicate which of the solubility rules covers each substanceâ€
> Using the general solubility rules given in Table 7.1, which of the following ions will form a precipitate with SO42-? a. Ba2+ b. Na+ c. NH4+ d. At least two of the above ions will form a precipitate with SO42-. e. All of the above ions will form a
> In a chemical reaction, the total number of atoms present after the reaction is complete is (larger than/smaller than/the same as) the total number of atoms present before the reaction began.
> For the unbalanced chemical equation HCl(g) + O2(g) H2O(g) + Cl2(g) a. list the reactant(s). b. list the product(s).
> If a sample of pure hydrogen gas is ignited very carefully, the hydrogen burns gently, combining with the oxygen gas of the air to form water vapor. Write the unbalanced chemical equation for this reaction.
> Balance the following chemical equations. MnO2(s) + CO(g) Mn2O3(aq) + CO2(g) Al(s) + H2SO4(aq) Al2(SO4)3(aq) + H2(g) C4H10(g) + O2(g) CO2(g) + H2O(l) NH4I(aq) + Cl2(g)
> Using different shapes to distinguish between different elements, draw a balanced equation for the following reaction at the microscopic level. NH3(g) + O2(g) NO(g) + H2O(g)
> Balance the following chemical equation: CuSO4(aq) + KI(s) CuI(s) + I2(s) + K2SO4(aq)
> Which of the following statements about chemical reactions is false? a. When balancing a chemical equation, all subscripts must be conserved. b. When one coefficient is doubled, the rest of the coefficients in the balanced equation must also be doubled
> When lead(II) sulfide is heated to high temperatures in a stream of pure oxygen gas, solid lead(II) oxide forms with the release of gaseous sulfur dioxide. Write the unbalanced chemical equation for this reaction.
> When copper(II) oxide is boiled in an aqueous solution of sulfuric acid, a strikingly blue solution of copper(II) sulfate forms along with additional water. Write the unbalanced chemical equation for this reaction.
> What are the substances to the left of the arrow in a chemical equation called? To the right of the arrow? What does the arrow itself mean?
> When solid red phosphorus, P4, is burned in air, the phosphorus combines with oxygen, producing a choking cloud of tetraphosphorus decoxide. Write the unbalanced chemical equation for this reaction.
> Which of the following statements is false for the reaction of hydrogen gas with oxygen gas to produce water? (a, b, and c represent coefficients) a H2(g) + b O2(g) c H2O(g) a. The ratio of “ayc” must always equal one. b. The sum o
> When a strip of magnesium metal is heated in oxygen, it bursts into an intensely white flame and produces a finely powdered dust of magnesium oxide. Write the unbalanced chemical equation for this process.
> A common lecture demonstration called “elephant’s toothpaste” demonstrates the reaction of hydrogen peroxide producing water and oxygen gas. Write the unbalanced chemical equation for this process.
> When finely divided solid sodium is dropped into a flask containing chlorine gas, an explosion occurs and a fine powder of sodium chloride is deposited on the walls of the flask. Write the unbalanced chemical equation for this process.
> When iron wire is heated in the presence of sulfur, the iron soon begins to glow, and a chunky, blue-black mass of iron(II) sulfide is formed. Write the unbalanced chemical equation for this reaction.
> If you had a “sour stomach,” you might try an over-the-counter antacid tablet to relieve the problem. Can you think of evidence that the action of such an antacid is a chemical reaction?
> Balance the following chemical equation. LiAlH4(s) + AlCl3(s) AlH3(s) + LiCl(s)
> If you’ve ever left bread in a toaster too long, you know that the bread eventually burns and turns black. What evidence is there that this represents a chemical process?
> Glass is a mixture of several compounds, but a major constituent of most glass is calcium silicate, CaSiO3. Glass can be etched by treatment with hydrogen fluoride: HF attacks the calcium silicate of the glass, producing gaseous and water-soluble product
> Write a balanced chemical equation for the complete combustion of pentene, C7H14. In combustion, pentene reacts with oxygen to produce carbon dioxide and water.
> A common experiment in introductory chemistry courses involves heating a weighed mixture of potassium chlorate, KClO3, and potassium chloride. Potassium chlorate decomposes when heated, producing potassium chloride and evolving oxygen gas. By measuring t
> When elemental boron, B, is burned in oxygen gas, the product is diboron trioxide. If the diboron trioxide is then reacted with a measured quantity of water, it reacts with the water to form what is commonly known as boric acid, B(OH)3. Write a balanced
> A common experiment to determine the relative reactivity of metallic elements is to place a pure sample of one metal into an aqueous solution of a compound of another metallic element. If the pure metal you are adding is more reactive than the metallic
> One method of producing hydrogen peroxide is to add barium peroxide to water. A precipitate of barium oxide forms, which may then be filtered off to leave a solution of hydrogen peroxide. Write the balanced chemical equation for this process.
> When steel wool (iron) is heated in pure oxygen gas, the steel wool bursts into flame and a fine powder consisting of a mixture of iron oxides (FeO and Fe2O3) forms. Write separate unbalanced equations for the reaction of iron with oxygen to give each of
> Iron oxide ores, commonly a mixture of FeO and Fe2O3, are given the general formula Fe3O4. They yield elemental iron when heated to a very high temperature with either carbon monoxide or elemental hydrogen. Balance the following equations for these proce
> The Hall process is an important method by which pure aluminum is prepared from its oxide (alumina, Al2O3) by indirect reaction with graphite (carbon). Balance the following equation, which is a simplified representation of this process. Al2O3(s) + C(s)
> You have probably had the unpleasant experience of discovering that a flashlight battery has gotten old and begun to leak. Is there evidence that this change is due to a chemical reaction?
> Methanol (methyl alcohol), CH3OH, is a very important industrial chemical. Formerly, methanol was prepared by heating wood to high temperatures in the absence of air. The complex compounds present in wood are degraded by this process into a charcoal resi
> The following demonstration takes place in a two-step process: First, solid calcium carbide (CaC2) reacts with liquid water to produce acetylene gas (C2H2) and aqueous calcium hydroxide. Second, the acetylene gas produced is then ignited with a match, ca
> 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 tw
> When balancing a chemical equation, which of the following statements is false? a. Subscripts in the reactants must be conserved in the products. b. Coefficients are used to balance the atoms on both sides. c. The law of conservation of matter must be
> Acetylene gas, C2H2, is used in welding because it generates an extremely hot flame when it is combusted with oxygen. The heat generated is sufficient to melt the metals being welded together. Carbon dioxide gas and water vapor are the chemical products
> In each of the following, identify which names are incorrect for the given formulas, and give the correct name. a. CuCl2, copper(I) chloride b. Ag2O, silver oxide c. Li2O, lithium oxide d. CaS, calcium(II) sulfide e. Cs2S, cesium sulfide
> Although this is no longer generally recommended, in the past, small cuts and abrasions on the skin were frequently cleaned using hydrogen peroxide solution. What evidence is there that treating a wound with hydrogen peroxide causes a chemical reaction t
> Balance the equation for the reaction of potassium with water. K(s) + H2O(l) H2(g) + KOH(aq) Aichard Megna/Fundamental Photographs © Cengage Learming
> The “Chemistry in Focus” segment The Beetle That Shoots Straight discusses the bombardier beetle and the chemical reaction of the decomposition of hydrogen peroxide. H2O2 (aq) H2O(l) + O2 (g) The balanced equation given in the s
> When balancing chemical equations, beginning students are often tempted to change the numbers within a formula (the subscripts) to balance the equation. Why is this never permitted? What effect does changing a subscript have?
> Nitric acid, HNO3, can be produced by reacting high-pressure ammonia gas with oxygen gas at around 750 °C in the presence of a platinum catalyst. Water is a by-product of the reaction. Write the unbalanced chemical equation for this process.
> The element tin often occurs in nature as the oxide, SnO2. To produce pure tin metal from this sort of tin ore, the ore usually is heated with coal (carbon). This produces pure molten tin, with the carbon being removed from the reaction system as the gas
> Although they were formerly called the inert gases, the heavier elements of Group 8 do form relatively stable compounds. For example, at high temperatures in the presence of an appropriate catalyst, xenon gas will combine directly with fluorine gas to pr
> Calcium oxide is sometimes very challenging to store in the chemistry laboratory. This compound reacts with moisture in the air and is converted to calcium hydroxide. If a bottle of calcium oxide is left on the shelf too long, it gradually absorbs moistu
> When elemental phosphorus, P4, burns in oxygen gas, it produces an intensely bright light, a great deal of heat, and massive clouds of white solid phosphorus(V) oxide (P2O5) product. Given these properties, it is not surprising that phosphorus has been u
> Although these days many people have “self-cleaning” ovens, if your oven gets really dirty you may have to resort to one of the spray-on oven cleaner preparations sold in supermarkets. What evidence is there that such oven cleaners work by a chemical rea
> In each of the following, identify which names are incorrect for the given formulas, and give the correct name. a. CaH2, calcium hydride b. PbCl2, lead(IV) chloride c. CrI3, chromium(III) iodide d. Na2S, disodium sulfide e. CuBr2, cupric bromide
> Carbon tetrachloride was widely used for many years as a solvent until its harmful properties became well established. Carbon tetrachloride may be prepared by the reaction of natural gas (methane, CH4) and elemental chlorine gas in the presence of ultrav
> There are fears that the protective ozone layer around the earth is being depleted. Ozone, O3, is produced by the interaction of ordinary oxygen gas in the atmosphere with ultraviolet light and lightning discharges. The oxides of nitrogen (which are comm
> 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 as a by-product. Write the unbalanced chemical equations for the reaction
> The burning of high-sulfur fuels has been shown to cause the phenomenon of “acid rain.” When a high-sulfur fuel is burned, the sulfur is converted to sulfur dioxide (SO2) and sulfur trioxide (SO3). When sulfur dioxide and sulfur trioxide gas dissolve in
> 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
> Solid zinc is added to an aqueous solution containing dissolved hydrogen chloride to produce gaseous hydrogen that bubbles out of the solution and zinc chloride that remains dissolved in the water. Write the unbalanced chemical equation for this process.
> Nitrous oxide gas (systematic name: dinitrogen monoxide) is used by some dental practitioners as an anesthetic. Nitrous oxide (and water vapor as by-product) can be produced in small quantities in the laboratory by careful heating of ammonium nitrate. Wr
> Pure silicon, which is needed in the manufacturing of electronic components, may be prepared by heating silicon dioxide (sand) with carbon at high temperatures, releasing carbon monoxide gas. Write the unbalanced chemical equation for this process.
> Phosphorus trichloride is used in the manufacture of certain pesticides and may be synthesized by direct combination of its constituent elements. Write the unbalanced chemical equation for this process.
> These days many products are available to whiten teeth at home. Many of these products contain a peroxide that bleaches stains from the teeth. What evidence is there that the bleaching process is a chemical reaction?
> Give the name of each of the following simple binary ionic compounds. a. LiI b. MgF2 c. SrO d. AlBr3 e. CaS f. Na2O
> The “Chemistry in Focus” segment Sugar of Lead discusses Pb(C2H3O2)2, which originally was known as sugar of lead. a. Why was it called sugar of lead? b. What is the systematic name for Pb(C2H3O2)2? c. Why is it necessary to have a system for the nami
> Write the name of each of the following ionic substances, using the system that includes a Roman numeral to specify the charge of the cation. a. FeI3 b. MnCl2 c. HgO d. Cu2S e. CoO f. SnBr4
> Write the name of each of the following ionic substances, using the system that includes a Roman numeral to specify the charge of the cation. a. SnCl4 b. Fe2S3 c. PbO2 d. Cr2S3 e. CuO f. Cu2O
> On the basis of the general solubility rules given in Table 7.1, predict which of the following substances are likely to be appreciably soluble in water. Indicate which specific rule(s) led to your conclusion. a. Ba(NO3)2 b. K2SO4 c. PbSO4 d. Cu(OH)2
> On the basis of the general solubility rules given in Table 7.1, predict which of the following substances are not likely to be soluble in water. Indicate which specific rule(s) led to your conclusion. a. PbS b. Mg(OH)2 c. Na2SO4 d. (NH4)2S e. BaCO3
> A member of the alkali metal family whose most stable ion contains 36 electrons forms a compound with chlorine. What is the correct formula for this compound?
> Write the name of each of the following ionic substances, using the system that includes a Roman numeral to specify the charge of the cation. a. FeBr2 b. CoS c. Co2S3 d. SnO2 e. Hg2Cl2 f. HgCl2
> Which of the following statements about chemical equations is (are) true? a. When balancing a chemical equation, you can never change the coefficient in front of any chemical formula. b. The coefficients in a balanced chemical equation refer to the num
> For the following pairs of ions, use the principle of electrical neutrality to predict the formula of the binary compound that the ions are most likely to form. a. Na+ and S2- b. K+ and Cl- c. Ba2+ and O2- d. Mg2+ and Se2- e. Cu2+ and Br- f. Al3+ an
> For each of the following atomic numbers, use the periodic table to write the formula (including the charge) for the simple ion that the element is most likely to form. a. 36 b. 31 c. 52 d. 81 e. 35 f. 87
> Suppose you are trying to help your friend understand the general solubility rules for ionic substances in water. Explain in general terms to your friend what the solubility rules mean, and give an example of how the rules could be applied in determining
> Balance each of the following chemical equations. a. SiCl4(l) + Mg(s) Si(s) + MgCl2(s) b. NO(g) + Cl2(g) NOCl(g) c. MnO2(s) + Al(s) Mn(s) + Al2O3(s) d. Cr(s) + S8(s)
> Balance each of the following chemical equations. a. Cl2(g) + KBr(aq) Br2 (l) + KCl(aq) b. Cr(s) + O2 (g) Cr2O3(s) c. P4(s) + H2 (g) PH3(g) d. Al(s) + H2SO4(aq)
> Complete Table 5.B by writing the formulas for the ionic compounds formed when the anions listed across the top combine with the cations shown in the left-hand column. Table 5.B hydrogen sulfate dihydrogen phosphate Ions nitrate sulfate oxide chlorid
> Complete Table 5.A by writing the names and formulas for the ionic compounds formed when the cations listed across the top combine with the anions shown in the left-hand column. Table 5.A Ions Fe2+ A3+ Na+ Ca2+ NH,+ Fe3+ Ni2+ Hg,2+ Hg²+ CO,2- BrOz C,
