3. Chemical Reactions

A 70.0-g iron nail combines with 30.0 g of oxygen to form rust. What is the total mass of the iron nail plus the rust that forms?

A nitrogen oxide is 63.65% by mass nitrogen. The molecular formula could be:

The following data were collected when analyzing a compound used in dentistry as a cement to repair teeth:

50.82% Zn; 16.04% P; 33.14% O

What is the empirical formula of the compound?

Based on the amounts of reactants used the calculated amount of product that can form for a given reaction was 20.76 g. When the reaction was carried out in a laboratory 17.34 g of product was recovered. What is the percent yield for this reaction?

Rubbing alcohol is a 90% (by mass) solution of isopropyl alcohol, C3H8O, in water. How many moles of isopropyl alcohol are in 50.0 g of rubbing alcohol? (LO 13.4) (a) 45 mol

Glycine, an amino acid used by organisms to make proteins, is represented by the following molecular model. (d) Calculate the percent nitrogen by mass in glycine.

What is the percent composition by mass of Mn in potas-sium permanganate, KMnO4? (LO 3.10) (a) 22.6% (b) 34.8% (c) 49.9% (d) 54.9%

Calculate the percentage by mass of oxygen in the following compounds: (e) dioxin, C12H4Cl4O2

Calculate the percentage by mass of oxygen in the following compounds: (f) penicillin, C16H18N2O4S.

Calculate the percentage by mass of oxygen in the following compounds: (c) acetaminophen, C8H9NO2

Calculate the percentage by mass of oxygen in the following compounds: (b) isopropyl alcohol, C3H8O

Calculate the percentage by mass of oxygen in the following compounds: (a) vanillin, C8H8O3

Calculate the percentage by mass of the indicated element in the following compounds: (a) hydrogen in methane, CH4, the major hydrocarbon in natural gas

Calculate the percentage by mass of the indicated element in the following compounds: (f) carbon in sucrose, C12H22O11, the compound that is responsible for the sweet taste of table sugar.

Calculate the percentage by mass of the indicated element in the following compounds: (e) oxygen in the insect pheromone sulcatol, C8H16O

Calculate the percentage by mass of the indicated element in the following compounds: (d) nitrogen in epinephrine, C9H13NO3 , also known as adrenalin, a hormone that is important for the fightor- flight response

Calculate the percentage by mass of the indicated element in the following compounds: (c) sulphur in magnesium sulphate, MgSO4, a substance used as a drying agent

Calculate the percentage by mass of the indicated element in the following compounds: (b) oxygen in vitamin E, C29H50O2

Based on the following structural formulas, calculate the percentage of carbon by mass present in each compound: (a) Benzaldehyde (almond fragrance) (b) Vanillin (vanilla flavor) c) Isopentyl acetate (banana flavor)

Calculate the percentage of carbon by mass in each of the compounds represented by the following models: (a)

What is the percent composition of cysteine, one of the 20 amino acids commonly found in proteins? (Gray = C, red = O, blue = N, yellow = S, ivory = H.)

(a) Calculate the mass percentage of Na2SO4 in a solution containing 10.6 g of Na2SO4 in 483 g of water.

A compound whose empirical formula is XF3 consists of 65% F by mass. What is the atomic mass of X?

The compound XCl4 contains 75.0% Cl by mass. What is the element X?

Calculate the number of moles of solute present in each of the following aqueous solutions: (c) 124.0 g of a solution that is 6.45% glucose 1C6H12O62 by mass.

An aqueous NaCl solution is made using 112 g of NaCl diluted to a total solution volume of 1.00 L. Calculate the mass percent of the solution. (Assume a density of 1.08 g>mL for the solution.)

An aqueous KNO3 solution is made using 72.5 g of KNO3 diluted to a total solution volume of 2.00 L. Calculate the mass percent of the solution. (Assume a density of 1.05 g>mL for the solution.)

Silver nitrate solutions are often used to plate silver onto other metals. What is the maximum amount of silver (in grams) that can be plated out of 4.8 L of an AgNO3 solution containing 3.4% Ag by mass? Assume that the density of the solution is 1.01 g>mL.

A dioxin-contaminated water source contains 0.085% dioxin by mass. How much dioxin is present in 2.5 L of this water? Assume a density of 1.00 g>mL.

A sample that weighs 25.12 g contains 6.022 * 10^23 particles. If 25.00% of the total number of particles are argon atoms and 75.00% are another element, what is the chemical identity of the other constituent?

Lead is a toxic metal that affects the central nervous system. A Pb-contaminated water sample contains 0.0011% Pb by mass. How much of the water (in mL) contains 150 mg of Pb? (Assume a density of 1.0 g>mL.)

Propenoic acid, C3H4O2, is a reactive organic liquid that is used in the manufacturing of plastics, coatings, and adhesives. An unlabeled container is thought to contain this liquid. A 0.275-g sample of the liquid is combusted to produce 0.102 g of water and 0.374 g carbon dioxide. Is the unknown liquid propenoic acid? Support your reasoning with calculations.

Iron metal can be produced from the mineral hematite, Fe2O3, by reaction with carbon. How many kilograms of iron are present in 105 kg of hematite?

Describe how to prepare each solution from the dry solute and the solvent. c. 125 g of 1.0% NaNO3 solution by mass

A solution is prepared by dissolving 20.2 mL of methanol (CH3OH) in 100.0 mL of water at 25 °C. The final volume of the solution is 118 mL. The densities of methanol and water at this temperature are 0.782 g>mL and 1.00 g>mL, respectively. For this solution, calculate the concentration in each unit. c. percent by mass

Calculate the mass percent composition of carbon in each carbon-containing compound. c. C2H2

Calculate the mass percent composition of carbon in each carbon-containing compound. d. C2H5Cl

Calculate the mass percent composition of carbon in each carbon-containing compound. a. CH4

Calculate the mass percent composition of nitrogen in each nitrogen-containing compound. c. NO2

Calculate the mass percent composition of nitrogen in each nitrogen-containing compound. a. N2O

Most fertilizers consist of nitrogen-containing compounds such as NH3, CO(NH2)2, NH4NO3, and (NH4)2SO4. Plants use the nitrogen content in these compounds for protein synthesis. Calculate the mass percent composition of nitrogen in CO(NH2)2.

Iron in the earth is in the form of iron ore. Common ores include Fe2O3 (hematite), Fe3O4 (magnetite), and FeCO3 (siderite). Calculate the mass percent composition of iron for each of these iron ores. Which ore has the highest iron content?

Copper(II) fluoride contains 37.42% F by mass. Calculate the mass of fluorine (in g) in 55.5 g of copper(II) fluoride.

Silver chloride, often used in silver plating, contains 75.27% Ag by mass. Calculate the mass of silver chloride required to plate 155 mg of pure silver.

The iodide ion is a dietary mineral essential to good nutrition. In countries where potassium iodide is added to salt, iodine deficiency (or goiter) has been almost completely eliminated. The recommended daily allowance (RDA) for iodine is 150 mg/day. How much potassium iodide (76.45% I) should you consume if you want to meet the RDA?

Li-ion batteries used in automobiles typically use a LiMn2O4 cathode in place of the LiCoO2 cathode found in most Li-ion batteries. (a) Calculate the mass percent lithium in each electrode material.

Saline solution used in hospital contains 0.9% sodium chloride by mass. Calculate the number of grams of sodium chloride in 0.5 gal of saline solution if the solution has a density of 1.01 g/mL.

Urea, a substance commonly used as a fertilizer, has the for-mula CH4N2O. What is its percent composition by mass?

Calculate the mass percent composition of each of the following substances. (b) Acetaminophen, a headache remedy: C8H9NO2

Calculate the mass percent composition of each of the following substances. (a) Malachite, a copper-containing mineral: Cu2(OH)2CO3

Calculate the mass percent composition of each of the following substances. (c) Prussian blue, an ink pigment: Fe4[Fe(CN)6]3

Calcium is an essential nutrient in our body. It is important for bone health. Four common calcium-containing supplements are calcium carbonate (CaCO3), calcium citrate (Ca3C12H10O14), calcium gluconate (CaC12H22O14), and calcium lactate (CaC6H10O6). Rank these calcium supplements in terms of the mass percentage of calcium they contain.

(b) Hemoglobin, the oxygen-carrying protein in red blood cells, has four iron atoms per molecule and contains 0.340% iron by mass. Calculate the molar mass of hemoglobin.

A compound, Na2Cr2Ox, where x is unknown, is analyzed and found to contain 39.70% Cr. What is the value of x?

Water softeners often replace calcium ions in hard water with sodium ions. Since sodium compounds are soluble, the presence of sodium ions in water does not cause the white, scaly residues caused by calcium ions. However, calcium is more beneficial to human health than sodium because calcium is a necessary part of the human diet, while high levels of sodium intake are linked to increases in blood pressure. The U.S. Food and Drug Administration (FDA) recommends that adults ingest less than 2.4 g of sodium per day. How many liters of softened water, containing a sodium concentration of 0.050% sodium by mass, would a person have to consume to exceed the FDA recommendation? (Assume a water density of 1.0 g>mL.)

When magnesium metal is burned in air (Figure 3.6), two products are produced. One is magnesium oxide, MgO. The other is the product of the reaction of Mg with molecular nitrogen, magnesium nitride. When water is added to magnesium nitride, it reacts to form magnesium oxide and ammonia gas. (c) In an experiment, a piece of magnesium ribbon is burned in air in a crucible. The mass of the mixture of MgO and magnesium nitride after burning is 0.470 g. Water is added to the crucible, further reaction occurs, and the crucible is heated to dryness until the final product is 0.486 g of MgO. What was the mass percentage of magnesium nitride in the mixture obtained after the initial burning?

A mixture of FeO and Fe2O3 with a mass of 10.0 g is con-verted to 7.43 g of pure Fe metal. What are the amounts in grams of FeO and Fe2O3 in the original sample?

A copper wire having a mass of 2.196 g was allowed to react with an excess of sulfur. The excess sulfur was then burned, yielding SO2 gas. The mass of the copper sulfide produced was 2.748 g. (a) What is the percent composition of copper sulfide?

The nitrogen in sodium nitrate and in ammonium sulfate is available to plants as fertilizer. Which is the more economical source of nitrogen, a fertilizer containing 30.0% sodium nitrate by weight and costing $9.00 per 100 lb or one containing 20.0% ammonium sulfate by weight and costing $8.10 per 100 lb?

Element X, a member of group 5A, forms two chlorides, XCl3 and XCl5. Reaction of an excess of Cl2 with 8.729 g of XCl3 yields 13.233 g of XCl5. What is the atomic weight and the identity of the element X?

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. d. cobalt(II) bromide

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. c. sulfurous acid

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. b. lead(II) phosphate

Pure gold is usually too soft for jewelry, so it is often alloyed with other metals. How many gold atoms are in an 0.255- ounce, 18 K gold bracelet? (18 K gold is 75% gold by mass.)

The karat scale used to describe gold alloys is based on mass percentages. (b) If an alloy is formed that is 50 mol% copper and 50 mol% gold, what is the karat number of the alloy? What is the color of this alloy?

The karat scale used to describe gold alloys is based on mass percentages. (a) If an alloy is formed that is 50 mol% silver and 50 mol% gold, what is the karat number of the alloy? Use Figure 12.18 to estimate the color of this alloy.

Determine the chemical formula of each compound and then use it to calculate the mass percent composition of each constituent element. c. nitrogen triiodide

A metal (M) forms a compound with the formula MCl3. If the compound contains 65.57% Cl by mass, what is the identity of the metal?

A metal (M) forms an oxide with the formula M2O. If the oxide contains 16.99% O by mass, what is the identity of the metal?

A phosphorus compound that contains 34.00% phosphorus by mass has the formula X3P2. Identify the element X.

A particular brand of beef jerky contains 0.0552% sodium nitrite by mass and is sold in an 8.00-oz bag. What mass of sodium does the sodium nitrite contribute to the sodium content of the bag of beef jerky?

Phosphorus is obtained primarily from ores containing calcium phosphate. If a particular ore contains 57.8% calcium phosphate, what minimum mass of the ore must be processed to obtain 1.00 kg of phosphorus?

The mass percent of an element in a compound is the mass of the element (total mass of the element's atoms in the com-pound) divided by the mass of the compound (total mass of all atoms in the compound) times 100%. What is the mass per-cent of each element in acetaminophen? (See Problem 2.170.)

Calculate the mass percent composition of nitrogen in each of the following nitrogen compounds.

A compound whose empirical formula is xf3 consists of 65% f by mass.

Calculate the experimental mass % of c and h in the unknown liquid used in the experiment.