Chapter 2

Give the total number of atoms of each element in each of these molecules. (a) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{COOC}_{2} \mathrm{H}_{5}\) (b) \(\mathrm{HOOCCH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\) (c) \(\mathrm{NH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH}\) (d) \(\mathrm{C}_{10} \mathrm{H}_{9} \mathrm{NH}_{2} \mathrm{Fe}\) (e) \(\mathrm{C}_{6} \mathrm{H}_{2} \mathrm{CH}_{3}\left(\mathrm{NO}_{2}\right)_{3}\)

Give the correct name for each compound. (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{CCl}_{4}\) (c) \(\mathrm{P}_{4} \mathrm{~S}_{10}\) (d) \(\mathrm{SF}_{4}\)

Give the correct name for each compound. (a) \(\mathrm{HBr}\) (b) \(\mathrm{ClF}_{3}\) (c) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) (d) \(\mathrm{BI}_{3}\)

Write the correct formula for each compound. (a) Nitrogen triiodide (b) Carbon disulfide (c) Dinitrogen tetraoxide (d) Selenium hexafluoride

Write the correct formula for each compound. (a) Bromine trichloride (b) Xenon trioxide (c) Diphosphorus tetrafluoride (d) Oxygen difluoride

In a noncyclic alkane other than methane, what is the maximum number of hydrogen atoms that can be bonded to one carbon atom?

In a noncyclic alkane, what is the maximum number of carbon atoms that can be bonded to one carbon atom?

Consider two molecules that are constitutional isomers. (a) What is the same on the molecular level between these two molecules? (b) What is different on the molecular level between these two molecules?

Draw structural formulas for the five constitutional isomers of \(\mathrm{C}_{6} \mathrm{H}_{14}\)

The noncyclic hydrocarbon eicosane has 20 carbon atoms in each molecule. How many hydrogen atoms are in each molecule?

A cyclic hydrocarbon has 16 hydrogen atoms in each molecule. How many carbon atoms are there per molecule? What is the name of the compound?

If you divide Avogadro's number of pennies among the nearly 300 million people in the United States, and if each person could count one penny each second every day of the year for eight hours per day, calculate how long it would take to count the pennies.

Why do you think it is more convenient to use some chemical counting unit when doing calculations (chemists have adopted the unit of the mole, but it could have been something different) rather than using individual molecules?

Calculate the mass of (a) \(2.5 \mathrm{~mol}\) boron (b) \(0.015 \mathrm{~mol} \mathrm{O}_{2}\) (c) \(1.25 \times 10^{-3} \mathrm{~mol}\) iron (d) \(653 \mathrm{~mol}\) helium

Calculate the mass of (a) 6.03 mol gold (b) 0.045 mol uranium (c) \(15.6 \mathrm{~mol} \mathrm{Ne}\) (d) \(3.63 \times 10^{-4} \mathrm{~mol}\) plutonium

Calculate the amount of substance for each sample: (a) \(16.0 \mathrm{~g} \mathrm{Na}\) (b) \(0.0034 \mathrm{~g}\) platinum (c) \(1.54 \mathrm{~g} \mathrm{P}\) (d) \(0.876 \mathrm{~g}\) arsenic (e) \(0.983 \mathrm{~g} \mathrm{Xe}\)

If you have a \(35.67-\mathrm{g}\) piece of chromium metal on your car, calculate how many chromium atoms you have.

If you have a ring that contains \(1.94 \mathrm{~g}\) gold, calculate how many gold atoms are in the ring.

You have a pure sample of the antiseptic aminacrine, \(\mathrm{C}_{13} \mathrm{H}_{10} \mathrm{~N}_{2}\) (a) Calculate the mass in grams of 0.06500 mol aminacrine. (b) Calculate the number of aminacrine molecules in a \(0.2480-\mathrm{g}\) sample. (c) Calculate the number of nitrogen atoms in this \(0.2480-\mathrm{g}\) sample. (d) Calculate the mass of \(\mathrm{N}\) in 100 . \(\mathrm{g}\) aminacrine.

You have a pure sample of apholate, \(\mathrm{C}_{12} \mathrm{H}_{24} \mathrm{~N}_{9} \mathrm{P}_{3},\) a highly effective commercial insecticide. (a) Calculate the molar mass of apholate. (b) Calculate the mass of \(\mathrm{N}\) in 100 . \(\mathrm{g}\) apholate. (c) A sample containing \(250.0 \mathrm{mg}\) apholate is sprayed on an agricultural field. Calculate the mass of phosphorus in this sample of apholate; express your result in grams. (d) Calculate the number of phosphorus atoms in this sample of apholate.

You have a U. S. penny that weighs \(2.458 \mathrm{~g}\) and contains \(2.40 \%\) copper by mass. (a) Calculate the number of pennies needed to contain \(2.458 \mathrm{~g} \mathrm{Cu}\) (b) Calculate the amount of copper in the penny. (c) Calculate the number of copper atoms in the penny.

You have a sterling silver fork that contains \(92.5 \%\) silver and weighs \(43.2 \mathrm{~g}\). (a) Calculate the mass of silver in the fork. (b) Calculate the amount of silver in the fork. (c) Calculate the number of silver atoms in the fork.

Calculate the amount of substance in \(1.00 \mathrm{~g}\) of each compound. (a) \(\mathrm{CH}_{3} \mathrm{OH},\) methanol (b) \(\mathrm{Cl}_{2} \mathrm{CO},\) phosgene, a poisonous gas (c) Ammonium nitrate (d) Magnesium sulfate heptahydrate (Epsom salt) (e) Silver acetate

Acetaminophen, an analgesic, has the molecular formula \(\mathrm{C}_{8} \mathrm{H}_{9} \mathrm{O}_{2} \mathrm{~N}\) (a) Calculate the molar mass of acetaminophen. (b) Calculate the amount of acetaminophen in \(5.32 \mathrm{~g}\) acetaminophen. (c) Calculate the mass of acetaminophen in \(0.166 \mathrm{~mol}\) acetaminophen.

Calculate how many water molecules are in one drop of water. (One drop of water is \(\frac{1}{20} \mathrm{~mL},\) and the density of water is \(1.0 \mathrm{~g} / \mathrm{mL}\).)

Calculate the molar mass of each of these compounds and the mass percent of each element. (a) PbS, lead(II) sulfide, galena (b) \(\mathrm{C}_{2} \mathrm{H}_{6},\) ethane, a hydrocarbon fuel (c) \(\mathrm{CH}_{3} \mathrm{COOH}\), acetic acid, an important ingredient in vinegar (d) \(\mathrm{NH}_{4} \mathrm{NO}_{3}\), ammonium nitrate, a fertilizer

Three oxygen-containing compounds of iron are \(\mathrm{FeCO}_{3}\), \(\mathrm{Fe}_{2} \mathrm{O}_{3},\) and \(\mathrm{Fe}_{3} \mathrm{O}_{4} \cdot\) Calculate the percent iron by mass in each iron compound.

The copper-containing compound \(\mathrm{Cu}\left(\mathrm{NH}_{3}\right)_{4} \mathrm{SO}_{4} \cdot \mathrm{H}_{2} \mathrm{O}\) is a beautiful blue solid. Calculate the molar mass of the compound and the mass percent of each element.

The compound \(\mathrm{Co}\left(\mathrm{NO}_{3}\right)_{2} \cdot 6 \mathrm{H}_{2} \mathrm{O}\) is a red solid that absorbs water from the atmosphere. Calculate its molar mass and the mass percent of each element. Also calculate the mass percent water.

Quinine (molar mass \(=324.41 \mathrm{~g} / \mathrm{mol}\) ) is used as a cardiac depressant. It has this percent composition by mass: \(74.04 \% \mathrm{C} ; 7.46 \% \mathrm{H} ; 8.64 \% \mathrm{~N} ;\) and \(9.86 \%\) O. Use these data to determine (a) the empirical formula and (b) the molecular formula of quinine.

About a century ago, Paul Ehrlich discovered Salvarsan, the first arsenical antibiotic that cured a targeted disease, syphilis. The compound was the six hundred and sixth compound he tried against the disease, but the first one found to be effective against it. The compound has molar mass \(549.102 \mathrm{~g} / \mathrm{mol}\) and this mass percent composition: \(39.37 \% \mathrm{C} ; 3.304 \% \mathrm{H} ; 7.653 \% \mathrm{~N} ;\) \(8.741 \% \mathrm{O} ; 40.93 \% \mathrm{As}\) (a) Calculate the empirical formula of Salvarsan. (b) Determine the molecular formula of this compound.

The mineral uraninite is a uranium oxide that is \(84.80 \%\) uranium by mass. Show calculations to determine the correct empirical formula of uraninite.

Carbonic anhydrase, an important enzyme in mammalian respiration, is a large zinc-containing protein with a molar mass of \(3.00 \times 10^{4} \mathrm{~g} / \mathrm{mol}\). The zinc is \(0.218 \%\) by mass of the protein. Determine how many zinc atoms each carbonic anhydrase molecule contains.

Nitrogen fixation in the root nodules of peas and other legumes occurs with a reaction involving a molybdenumcontaining enzyme named nitrogenase. This enzyme contains two Mo atoms per molecule and is \(0.0872 \%\) Mo by mass. Calculate the molar mass of the enzyme.

Disilane, \(\mathrm{Si}_{2} \mathrm{H}_{x},\) contains \(90.28 \%\) silicon by mass. Calculate the value of \(x\) in this compound.

Chalky, white crystals in mineral collections are often labeled borax, which has the molecular formula \(\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \cdot 10 \mathrm{H}_{2} \mathrm{O},\) when actually they are partially dehydrated samples with the molecular formula \(\mathrm{Na}_{2} \mathrm{~B}_{4} \mathrm{O}_{7} \cdot 5 \mathrm{H}_{2} \mathrm{O},\) which is more stable under the storage conditions. Real crystals of borax are colorless and transparent. (a) Calculate the percent mass that the mineral has lost when it partially dehydrates. (b) Is the percent boron by mass the same in both compounds?

A well-known reagent in analytical chemistry, dimethylglyoxime, has the empirical formula \(\mathrm{C}_{2} \mathrm{H}_{4} \mathrm{NO} .\) If its molar mass is \(116.1 \mathrm{~g} / \mathrm{mol}\), determine the molecular formula of the compound.

The molecular formula of ascorbic acid (vitamin \(\mathrm{C}\) ) is \(\mathrm{C}_{6} \mathrm{H}_{8} \mathrm{O}_{6} .\) What is its empirical formula?

The alum used in cooking is potassium aluminum sulfate hydrate, \(\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2} \cdot x \mathrm{H}_{2} \mathrm{O} .\) To find the value of \(x,\) you can heat a sample of the compound to drive off all the water and leave only \(\mathrm{KAl}\left(\mathrm{SO}_{4}\right)_{2}\). Assume that you heat \(4.74 \mathrm{~g}\) of the hydrated compound and that it loses \(2.16 \mathrm{~g}\) water. Calculate the value of \(x\).

The density of a solution of sulfuric acid is \(1.285 \mathrm{~g} / \mathrm{cm}^{3}\), and it is \(38.08 \%\) acid by mass. Calculate the volume of the acid solution (in mL) you need to supply \(125 \mathrm{~g}\) of sulfuric acid.

The cancer drug cisplatin contains \(65.0 \%\) platinum. If you have \(1.53 \mathrm{~g}\) of the compound, calculate how many grams of platinum the sample contains.

Ethyl alcohol, \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\), has a density of \(0.789 \mathrm{~g} / \mathrm{mL}\) at \(25^{\circ} \mathrm{C}\). Water weighs \(1.00 \mathrm{~kg} / \mathrm{L}\) at \(25^{\circ} \mathrm{C}\). Calculate the volume of ethanol that contains the same number of molecules as \(1.00 \mathrm{~L}\) water.

The fluoridation of city water supplies has been practiced in the United States for several decades because there is scientific evidence that fluoride prevents tooth decay, especially in young children. Fluoridation is done by continuously adding sodium fluoride to water as it comes from a reservoir. Assume you live in a medium-sized city of 150,000 people and that each person uses 175 gal water per day. Calculate how many tons of sodium fluoride you must add to the water supply each year (365 days) to have the required fluoride concentration of 1 part per million (that is, 1 ton of fluoride per million tons of water). (Sodium fluoride is \(45.0 \%\) fluoride, and U. S. gallon of water has a mass of 8.34 lb.)

Which one of these symbols conveys more information about the atom: \({ }^{37} \mathrm{Cl}\) or \({ }_{17} \mathrm{Cl}\) ? Explain.

The Statue of Liberty in New York harbor is made of \(2.00 \times 10^{5} \mathrm{lb}\) copper sheets bolted to an iron framework. Calculate the mass and the amount of copper in the statue \((1 \mathrm{lb}=454 \mathrm{~g})\)

Two different halogens are present in a series known as interhalogen compounds. Name these interhalogen compounds: (a) IBr; (b) \(\mathrm{BrF}_{3} ;\) (c) \(\mathrm{I}_{2} \mathrm{Cl}_{6} ;\) (d) \(\mathrm{ClF}_{5}\); (e) IF \(_{7}\).

It's final exam time and a student drinks a 1.93 -oz bottle of 5-Hour Energy \(\mathbb{B}\) to stay awake. The drink contains, among other substances, \(212 \mathrm{mg}\) caffeine, \(\mathrm{C}_{8} \mathrm{H}_{10} \mathrm{~N}_{4} \mathrm{O}_{2}\) (a) Calculate the mass percent nitrogen in caffeine. (b) Calculate the number of caffeine molecules that the student ingested. (c) Calculate the number of carbon atoms in this mass of caffeine. (d) An 8-oz cup of regular coffee contains approximately \(100 \mathrm{mg}\) caffeine. Calculate how many times greater the caffeine concentration (mg/oz) is in the 5 -Hour Energy \(^{\oplus}\) drink than in the regular coffee.

(a) Calculate the mass of one molecule of nitrogen. (b) Calculate the mass of one molecule of oxygen. (c) Calculate the ratio of masses of these two molecules. How does it compare with the ratio of the atomic weights of \(\mathrm{N}\) and \(\mathrm{O}\) ?

For each pair of elements, (i) through (vii), (a) Determine whether an ionic compound, a molecular compound, or no compound would form. (b) Write an appropriate formula for each compound you expect to form and name the compound. (i) \(\quad\) Chlorine and bromine (ii) \(\quad\) Lithium and tellurium (iii) Sodium and argon (iv) \(\quad\) Magnesium and fluorine (v) Nitrogen and bromine (vi) \(\quad\) Indium and sulfur (vii) Selenium and bromine

For each substance, (i) through (viii), (a) Write the correct formula. (b) Decide whether the substance is ionic or molecular. (i) \(\quad\) Sodium hypochlorite (ii) \(\quad\) Tetraphosphorus decaoxide (iii) \(\quad\) Potassium permanganate (iv) \(\quad\) Potassium dihydrogen phosphate (v) \(\quad\) Chlorine trifluoride (vi) \(\quad\) Boron tribromide (vii) \(\quad\) Calcium acetate (viii) Sodium sulfite