Chemical Formulas and Chemical Formulas and Chemical CompoundsChemical Compounds

Chapter 7 Review – AnswersChapter 7 Review – Answers

Pages 53 - 54Pages 53 - 54

1.1. In a stock name In a stock name such as iron(III) such as iron(III) sulfate, the roman sulfate, the roman number tells us number tells us ____.____.

2.2. The result of The result of changing a changing a subscript in a subscript in a correctly written correctly written chemical formula chemical formula is to _____.is to _____.

C. The charge on each Fe C. The charge on each Fe ionion

C. Change the formula so C. Change the formula so that it no longer that it no longer represents the represents the compound it previously compound it previously represented.represented.

Pages 53 - 54Pages 53 - 543.3. The explosive TNT has the molecular The explosive TNT has the molecular

formula Cformula C77HH55(NO(NO22))33..

a.a. How many elements make up this compound?How many elements make up this compound?

b.b. How many oxygen atoms are present in one How many oxygen atoms are present in one molecule of Cmolecule of C77HH55(NO(NO22))33??

c.c. How many atoms in total are present in one How many atoms in total are present in one molecule of Cmolecule of C77HH55(NO(NO22))33??

d.d. How many atoms are present in a sample of 2 How many atoms are present in a sample of 2 10102323

molecules of Cmolecules of C77HH55(NO(NO22))3?3?

4 elements

6 oxygen atoms

21 atoms

atoms104.2molecule

atoms21molecules102 2423

Pages 53 - 54Pages 53 - 54

4.4. How many atoms are present in How many atoms are present in each of these formula units?each of these formula units?

a.a. Ca(HCOCa(HCO33))22

b.b. CC1212HH2222OO1111

c.c. Fe(ClOFe(ClO22))33

d.d. Fe(ClOFe(ClO33))22

11 atoms

45 atoms

10 atoms

9 atoms

Pages 53 - 54Pages 53 - 54

5.5. (see below)(see below)a.a. What is the formula for the compound What is the formula for the compound

dinitrogen pentoxide?dinitrogen pentoxide?

b.b. What is the Stock name for the What is the Stock name for the covalent compound CScovalent compound CS22??

N2O5

Carbon disulfide

Pages 53 - 54Pages 53 - 54

6.6. Some binary compounds are ionic, Some binary compounds are ionic, others are covalent. The types of others are covalent. The types of bonding partially depend on the bonding partially depend on the position of the elements in the position of the elements in the periodic table. Label each of these periodic table. Label each of these claims as True or False; if False, claims as True or False; if False, specify the nature of the error.specify the nature of the error.

a.a. Covalently bonded binary molecular Covalently bonded binary molecular compounds typically form from compounds typically form from nonmetals.nonmetals.

True

Pages 53 - 54Pages 53 - 54

6.6. Some binary compounds are ionic, Some binary compounds are ionic, others are covalent. The types of others are covalent. The types of bonding partially depend on the bonding partially depend on the position of the elements in the position of the elements in the periodic table. Label each of these periodic table. Label each of these claims as True or False; if False, claims as True or False; if False, specify the nature of the error.specify the nature of the error.

b.b. Binary ionic compound form from Binary ionic compound form from metals and nonmetals, typically from metals and nonmetals, typically from opposite sides of the periodic table.opposite sides of the periodic table.

True

Pages 53 - 54Pages 53 - 546.6. Some binary compounds are ionic, Some binary compounds are ionic,

others are covalent. The types of others are covalent. The types of bonding partially depend on the bonding partially depend on the position of the elements in the position of the elements in the periodic table. Label each of these periodic table. Label each of these claims as True or False; if False, claims as True or False; if False, specify the nature of the error.specify the nature of the error.

c.c. Binary compound involving metalloids Binary compound involving metalloids are always ionic.are always ionic.

False; metalloids on the right of the stair-step line act as nonmetals in compounds

Pages 53 - 54Pages 53 - 548.8. Fill in the blanks in the table below.Fill in the blanks in the table below.

Compound NameCompound Name FormulaFormula

Aluminum sulfideAluminum sulfide

Aluminum sulfiteAluminum sulfite

PbClPbCl22

(NH(NH44))33POPO44

Al2S3

Al2(SO3)3

Lead(II) chloride

Ammonium phosphate

Pages 55 - 56Pages 55 - 56

4.4. Tin has possible oxidation numbers Tin has possible oxidation numbers of +2 and +4 and forms two known of +2 and +4 and forms two known oxides. One of them has the oxides. One of them has the formula SnOformula SnO22..

a.a. Give the stock name for SnOGive the stock name for SnO22..

b.b. Give the empirical formula for the Give the empirical formula for the other oxide of tin.other oxide of tin.

Tin(IV) oxide

SnO

Pages 55 - 56Pages 55 - 565.5. Scientists believe that two separate reactions Scientists believe that two separate reactions

contribute to the depletion of the ozone layer, Ocontribute to the depletion of the ozone layer, O33. . The first reaction involves oxides of nitrogen. The The first reaction involves oxides of nitrogen. The second involves free chlorine atoms. Both reactions second involves free chlorine atoms. Both reactions follow. When a compound is not stated as a follow. When a compound is not stated as a formula, write the correct formula in the blank formula, write the correct formula in the blank beside its name.beside its name.

a.a. _____(nitrogen monoxide) + O_____(nitrogen monoxide) + O33 → ______ → ______

(nitrogen dioxide) + O(nitrogen dioxide) + O22

b.b. Cl + OCl + O33 → ______ (chlorine monoxide) + O→ ______ (chlorine monoxide) + O22

NO

ClO

NO2

Pages 55 - 56Pages 55 - 56

6.6. Consider the covalent dinitrogen Consider the covalent dinitrogen trioxide when answering the trioxide when answering the following:following:

a.a. What is the formula for dinitrogen What is the formula for dinitrogen trioxide?trioxide? N2O3

Pages 57 - 58Pages 57 - 581.1. Label each of the following statements as Label each of the following statements as

True or False:True or False:a.a. If the formula mass of one molecule is If the formula mass of one molecule is xx amu, amu,

the molar mass is the molar mass is x x g/mol.g/mol.

b.b. Samples of two different chemicals with Samples of two different chemicals with equal numbers of moles must have equal equal numbers of moles must have equal masses as well.masses as well.

c.c. Samples of two different chemicals with Samples of two different chemicals with equal numbers of moles must have equal equal numbers of moles must have equal numbers of molecules as well.numbers of molecules as well.

True

False

True

Pages 57 - 58Pages 57 - 582.2. How many moles of each element How many moles of each element

are present in a 10.0 mol sample of are present in a 10.0 mol sample of Ca(NOCa(NO33))22??

10.0 mol calcium

20.0 mol nitrogen

60.0 mol oxygen

Pages 57 - 58Pages 57 - 583.3. Consider a sample of 10.0 g of the gaseous Consider a sample of 10.0 g of the gaseous

hydrocarbon Chydrocarbon C33HH4 4 to answer the following to answer the following questions.questions.

a.a. How many moles are present in this sample?How many moles are present in this sample?

b.b. How many molecules are present in the CHow many molecules are present in the C33HH44 sample?sample?

mol 0.25g 40.0

molg 10.0

molecules101.50mol

molecules106.02mol 0.25 2323

Pages 57 - 58Pages 57 - 583.3. Consider a sample of 10.0 g of the gaseous Consider a sample of 10.0 g of the gaseous

hydrocarbon Chydrocarbon C33HH4 4 to answer the following to answer the following questions.questions.

c.c. How many carbon atoms are present in this How many carbon atoms are present in this sample?sample?

d.d. What is the percentage composition of hydrogen What is the percentage composition of hydrogen in the sample?in the sample?

atoms104.50molecule

atomscarbon 3molecules101.50 2323

10.0%H100HC

molg

40.0

Hmolg

4.0

43

Pages 57 - 58Pages 57 - 584.4. The chief source of aluminum metal is the The chief source of aluminum metal is the

ore alumina, Alore alumina, Al22OO33..

a.a. Determine the percentage composition of Al in Determine the percentage composition of Al in this ore.this ore.

b.b. How many pounds of aluminum can be How many pounds of aluminum can be extracted from 2.0 tons of alumina?extracted from 2.0 tons of alumina?

Al 52.9%100OAl

molg

102

Almolg

54

32

Al lb 0210ore lb 1

Al lb 0.529ore lbs 4000

Pages 57 - 58Pages 57 - 585.5. Compound A has a molar mass of 20 g/mol, and Compound A has a molar mass of 20 g/mol, and

compound B has a molar mass of 30 g/mol.compound B has a molar mass of 30 g/mol.

a.a. What is the mass of 1.0 mol of compound A?What is the mass of 1.0 mol of compound A?

b.b. How many moles are present in 5.0 g of How many moles are present in 5.0 g of compound B?compound B?

c.c. How many moles of compound B are needed to How many moles of compound B are needed to have the same mass as 6.0 mol of compound A?have the same mass as 6.0 mol of compound A?

mol 17.0g 30.0

molg 5.0

B mol 4B g 30

B molB g 120

A g 120A mol

A g 20A mol 6.0

20 grams

Pages 59 - 60Pages 59 - 601.1. Write empirical formulas to match Write empirical formulas to match

the following molecular formulas:the following molecular formulas:a.a. CC22HH66OO44

b.b. NN22OO55

c.c. HgHg22ClCl22

d.d. CC66HH1212

CH3O2

N2O5

HgCl

CH2

Pages 59 - 60Pages 59 - 60

2.2. A certain A certain hydrocarbon has an hydrocarbon has an empirical formula of empirical formula of CHCH22 and a molar and a molar mass of 56.12 mass of 56.12 g/mol. What is its g/mol. What is its molecular formula?molecular formula?

4

molg

0.14

molg

12.56

mol

g0.14

mol

g0.12

mol

g0.12

C4H8

Pages 59 - 60Pages 59 - 603.3. A certain ionic A certain ionic

compound is found compound is found to contain 0.012 mol to contain 0.012 mol of sodium, 0.012 mol of sodium, 0.012 mol of sulfur, and 0.018 of sulfur, and 0.018 mol of oxygen.mol of oxygen.

a.a. What is its empirical What is its empirical formula?formula?

b.b. Is this compound a Is this compound a sulfate, sulfite, or sulfate, sulfite, or neither?neither?

325.1012.0

O mol 0.018

221012.0

S mol 0.012

221012.0

Na mol .0120

Na2S2O3

neither

Pages 59 - 60Pages 59 - 605.5. Gas X is found to be 24.0% carbon and Gas X is found to be 24.0% carbon and

76.0% fluorine by mass.76.0% fluorine by mass.a.a. Determine the empirical formula of gas X.Determine the empirical formula of gas X.

22

F mol 4

molg

0.19

F g 6.07

12

C mol 2

molg

0.12

C g 0.24

CF2

Pages 59 - 60Pages 59 - 605.5. Gas X is found to be 24.0% carbon and Gas X is found to be 24.0% carbon and

76.0% fluorine by mass.76.0% fluorine by mass.b.b. Given that the molar mass of gas X is 200.04 Given that the molar mass of gas X is 200.04

g/mol, determine its molecular formula.g/mol, determine its molecular formula.

4

molg

50

molg

200

mol

g50

mol

g0.192

mol

g0.12

C4F8

Pages 59 - 60Pages 59 - 606.6. A compound is found to contain 43.2% A compound is found to contain 43.2%

copper, 24.1% chlorine and 32.7% oxygen copper, 24.1% chlorine and 32.7% oxygen by mass.by mass.

a.a. Determine its empirical formula.Determine its empirical formula.

36803.0

O mol 2.043

molg

0.16

O g 2.73

16803.0

Cl mol 0.6808

molg

4.35

Cl g 4.12

16803.0

Cu mol .68030

molg

5.63

Cu g 3.24

CuClO3

Pages 59 - 60Pages 59 - 606.6. A compound is found to contain 43.2% A compound is found to contain 43.2%

copper, 24.1% chlorine and 32.7% oxygen copper, 24.1% chlorine and 32.7% oxygen by mass.by mass.

b.b. What is the correct Stock name of the What is the correct Stock name of the compound in part a?compound in part a?

Copper(I) chlorate

Pages 61 - 64Pages 61 - 641.1. Write formulas for the following Write formulas for the following

compounds:compounds:a.a. Copper(II) carbonateCopper(II) carbonate

b.b. Sodium sulfiteSodium sulfite

c.c. Ammonium phosphateAmmonium phosphate

d.d. Tin(IV) sulfideTin(IV) sulfide

CuCO3

Na2SO3

(NH4)3PO4

SnS2

Pages 61 - 64Pages 61 - 642.2. Write the Stock names for the Write the Stock names for the

following compounds:following compounds:a.a. Mg(ClOMg(ClO44))22

b.b. Fe(NOFe(NO33))22

c.c. Fe(NOFe(NO22))33

d.d. CoOCoO

Magnesium perchlorate

Iron(II) nitrate

Iron(III) nitrite

Cobalt(II) oxide

Pages 61 - 64Pages 61 - 643.3. (see below)(see below)

a.a. How many atoms are representd by How many atoms are representd by the formula Ca(HSOthe formula Ca(HSO44))22??

b.b. How many moles of oxygen atoms are How many moles of oxygen atoms are in a 0.50 mol sample of this in a 0.50 mol sample of this compound?compound?

13

4 mol oxygen

Pages 61 - 64Pages 61 - 645.5. Following are samples of four Following are samples of four

different compounds. Arrange them different compounds. Arrange them in order of increasing mass, from in order of increasing mass, from smallest to largest.smallest to largest.

a.a. 25 g of oxygen gas25 g of oxygen gas

b.b. 1.00 mol of H1.00 mol of H22OO

c.c. 3 3 10 102323 molecules of Cmolecules of C22HH66

d.d. 2 2 10 102323 molecules of Cmolecules of C22HH66OO22

c, b, d, a

Pages 61 - 64Pages 61 - 646.6. (see below)(see below)

a.a. What is the formula for sodium What is the formula for sodium hydroxide?hydroxide?

b.b. What is the formula mass of sodium What is the formula mass of sodium hydroxide?hydroxide?

c.c. What is the mass in grams of 0.25 mol What is the mass in grams of 0.25 mol of sodium hydroxide?of sodium hydroxide?

NaOH

40 g/mol

10 grams

Pages 61 - 64Pages 61 - 647.7. What is the percentage composition What is the percentage composition

of ethane gas, Cof ethane gas, C22HH66, to the nearest , to the nearest whole number?whole number?

8.8. Ribose is an important sugar (part Ribose is an important sugar (part of RNA), with a molar mass of of RNA), with a molar mass of 150.15 g/mol. If its empirical 150.15 g/mol. If its empirical formula is CHformula is CH22O, what is its O, what is its molecular formula?molecular formula?

80% carbon, 20% hydrogen

C5H10O5

Pages 61 - 64Pages 61 - 649.9. Butane gas, CButane gas, C44HH1010, is often used as , is often used as

a fuel.a fuel.a.a. What is the mass in grams of 3.00 mol What is the mass in grams of 3.00 mol

of butane?of butane?

b.b. How many molecules are present in How many molecules are present in that 3.00 mol sample?that 3.00 mol sample?

c.c. What is the empirical formula of the What is the empirical formula of the gas?gas?

174 grams

1.81 1024 molecules

C2H5

Pages 61 - 64Pages 61 - 6410.10. Napthalene is a soft covalent solid Napthalene is a soft covalent solid

that is often used in mothballs. Its that is often used in mothballs. Its molar mass is 128.18 g/mol and it molar mass is 128.18 g/mol and it contains 93.75 % carbon and 6.25 contains 93.75 % carbon and 6.25 % hydrogen. Determine the % hydrogen. Determine the molecular formula of napthalene molecular formula of napthalene from this data.from this data.

C10H8

Pages 61 - 64Pages 61 - 6411.11. Nicotine has the formula CNicotine has the formula CxxHHyyNNzz. To determine . To determine

its composition, a sample is burned in excess its composition, a sample is burned in excess oxygen, producing the following results:oxygen, producing the following results:

1.0 mol of CO1.0 mol of CO22

0.70 mol of H0.70 mol of H22OO

0.20 mol of NO0.20 mol of NO22

Assume that all the atoms in nicotine are Assume that all the atoms in nicotine are present as products.present as products.

a.a. Determine the number of moles of carbon present in Determine the number of moles of carbon present in the products of this combustion.the products of this combustion.

b.b. Determine the number of moles of hydrogen present Determine the number of moles of hydrogen present in the products of this combustion.in the products of this combustion.

c.c. Determine the number of moles of nitrogen present in Determine the number of moles of nitrogen present in the products of this combustion.the products of this combustion.

1.0 mol C

1.4 mol H

0.2 mol N

Pages 61 - 64Pages 61 - 64

11.11. Nicotine has the formula CNicotine has the formula CxxHHyyNNzz. To determine . To determine its composition, a sample is burned in excess its composition, a sample is burned in excess oxygen, producing the following results:oxygen, producing the following results:

1.0 mol of CO1.0 mol of CO22

0.70 mol of H0.70 mol of H22OO

0.20 mol of NO0.20 mol of NO22

Assume that all the atoms in nicotine are Assume that all the atoms in nicotine are present as products.present as products.

d.d. Determine the empirical formula of nicotine based on Determine the empirical formula of nicotine based on your calculations.your calculations.

e.e. In a separate experiment, the molar mass of nicotine In a separate experiment, the molar mass of nicotine is found to be somewhere between 150 and 180 is found to be somewhere between 150 and 180 g/mol. Calculate the molar mass of nicotine to the g/mol. Calculate the molar mass of nicotine to the nearest gram.nearest gram.

C5H7N

162 g/mol