Name

CHAP1ER 7 REVIEW

Chems al Iormulas and Chemical Compounds

SECTION 1

SHORT ANSWER Answer the following questions in the space provided.

1. _ In a Stock system name such a iron Ill) sulfate. the Roman numeral tells us

(a> how many atoms of Fe are in one formula unit.b) how many sulfate ions can be attached to the iron atom.

(c) the charge on each Fe ion.(d) the total positive chargc of the formula unit

2. Changing a subscript in a correctly written chemical formula

(a) changes the number of moles represented by the formula.(b) changes the charges on the other ions in the compound.(c) changes the formula so that it no longer represents the compound it previously

represented.(d) has no effect on the formula.

3. The explosive TNT has the molecular formulaC7H5(N02)3.

4 elements

atoms

_______________________

a. Hoss many elements make up this compound?

b. How many oxygen atoms are present in one molecule ofC7H5(N02)3?

________________________

e. How many atoms in total are present in one molecule ofC7H5(N02)

________________________

d. How many atoms are present in a sample of 2.0 X 1023 moleculecofC7H5(N01h?

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

11 atoms a. Ca(HCO3),

45 atoms b. C12H22011

10 atoms c. Fe(Cl02)3

9 atoms d. Fe(Cl03)9

21 atoms

4.2 x 1024 atoms

5, ______N2_______iron(ll) oxide

H2S03

phosphoric acid

a. What is the formula for the compound dinitrogen pentoxide9

b. What is the Stock system name for the compound FeO?

c. What is the formula for sulfurous acid?

d. What is the name for the acid H3P04?

MODERN CHEMISTRYCo igit by Holt Rinehart d Wi st r 511 riizhts reser i

CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS 53

Name

_________ _____ _____ ______

Date

SECTION 1 ontinued

6 Some nary C( npoun e ior other r coa e Thc y e of fax parti kp.on the position of the elements in the periodic table Label e&h of thce claijn as True or False. iFalse. specify the nature of the error.

a. Cm aientiy bonded binary molecular compounds arL tpicaIly composed 01 n nmetais

True

b. Binary ionic compounds are composed of metals and nonmetals, typically from opposite sides ofthe periodic table.

True

7. Refer to Table 2 on page 226 of the text and Table 5 on page 230 of the text for examples ofnames and formulas for polyatomic ions and acids.

a. Derive a generalization for determining whether an acid name will end in the suffix u or -ous,

In general, if the anion name ends in -ate, the corresponding acid name will end in a

suffix of -Ic. In general, if the anion name ends in -ite, the corresponding acid name

will end in a suffix of -otis.

b. Denve a generalization for determining whether an acid name will begin with the prefix hi’drmor not.

In general, if the anion name ends in -ide, the corresponding acid name will end in a

-

8. Fill in the blanks in the table below.

Compound name Formula

Aluminum sulfide A1253

Cesium carbonate Cs2CO3

Lead(Il) chloride PbCI2

Ammonium phosphate (NH4)3P04

Hydrolodic acid

54 CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS

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MODERN CHEMISTRYCopright 0 h HoN Rirehart d \ nwn AN rtghts reered

Nay

____

Date

CHAPTIR 7 R EVIEWI

Chemical Formulas and Chemical Compounds

SECTION 2

SHORT ANSWER Answer the following questions in the space provided.

I Assign the oxidation number to the specified element in each of tfe following examples:

______

a. S in H2S03

JtL b. S in MgSO4

_____

c. SinK2S

+1 d. Cu in Cu2S

+6 e. Cr in Na,Cr04

+5 f.NinHNO

g. C in (HCO3)

3 h. Nin(NH4)

2. 5C12 a. What is the formula for the compound sulfur(ll) chloride?

nitrogen(IV) oxide b. What is the Stock system name for NO,?

3. fluorine a, Use electronegativity values to determine the one element thatalways has a negative oxidation number when it appears in anybinary compound.

0; F2 b. What is the oxidation number and formula for the element describedin part a when it exists as a pure element?

4. Tin has possible oxidation numbers of +2 and +4 and forms two known oxides. One of them hasthe formula Sn02,

tin(W) oxide a. Give the Stock system name for SnO2.

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

5. Scientists think that two separate reactions contribute to the depletion of the ozone, 03, layer. Thefirst reaction involves oxides of nitrogen. The second involves free chlorine atoms. The equationsthat represent the reactions follow. When a compound is not stated as a formula. write the correctformula in the blank beside its name.

a. NO (nitrogen monoxide) + 03 NO2 (nitrogen dioxide)

MODERN CHEMISTRY

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CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS 55Copwighi©by Ho Rhehar’ rdW m r All riglo r rved

_______ ______ _____

Date

SECTION 2 continued

b. Cl 0 brine Ofl( ide) 0

do alert i d d io ns tub

— a Wh c ormu I Itrogen e?

_________

b. What s the oxidation number assigned to each nitrogen atom in thiscompoundS? Explain your answer.

Thexy9natomshavcxidationstesof-6 total, and balebr!c

sum of the oxidation states in a ne corn ound must be zero, the two nitren

atoms must have_oxidation statec of +6 total,_therefor +3 each.

_____ _________

nitrogen(lll)_oxide c, Give the Stock name for dinitrogen rioxide.

7. The oxidation numbers assigned to the atoms in some organic compounds have unexpected values.Assign oxidation numbers to each atom in the following compounds: (Note: Some oxidationnumbers may not be whole numbers.)

a C0

is +4 and each ox gen is 2.

b. CH4 (methane)

Carbon is 4 and each hydrogen is ±1.

__________________ _____ ____

C. C6H12O(glucose)

Each carbon is 0, each hydrogen is +1, and each oxygen is —2.

d. CaH5 (propane gas)

Each carbon is —8/3 and

& Assign oxidation numbers to each element in the compounds found in the following situations:

a. Rust. FeO3, forms on an old nail.

Each iron is +3 and each oxygen is —2.

b. Nitrogen dioxide, NO2. pollutes the air as a component of smog.

Nitrogen is +4 and each oxygen is —2.

__________

c, Chromium dioxide, Cr02, is used to make recording tapes.

iumis+4andeachoxenis-2,

56 CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS

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MODERN CHEMISTRYrvnght S nehan a W t 55 riehn e r ed

ate

CHAPTER 7 REVIEW

Chemical Formulas and Chemical Compounds

SECTION 3

SHORT ANSWER Answer the following questions in the space provided.

1. Label each of the following statements as True or False:

________ _________

a. If the formula mass of one molecule is ainu, [he molar mass isa g/mol

False b. Samples of equal numbers of mole of tv o different hemi ‘alsmust have equal masses as well.

True c. Samples of equal numbers of moles of two different molecularcompounds must have equal numbers of molecules as well,

2. How many moles of each element are present in a 10.0 mol sample of Ca(NO)2?

10 mol of calcium, 20 mol of nitrogen, 60 mol of oxygen

PROBLEMS Write the answer on the line to the left. Show all your work in the spaceprovided.

3. Consider a sample of 10.0 g of the gaseous hydrocarbon C3H4 to answer the following questions.

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

1.50 x 1023 molecules b How many molecules are present in the C3H4 sample?

An it23 L.-. caron aLoms c. How many carbon atoms are present in this sample?

MODERN CHEMISTRY CHEMICAL._FORMULAS AND CHEMICAL COMPOUNDS 57Copyright Oh Huh R i r d V n n. AP nght d

Name_

____ ____

Date

____

_Cia.

SECTION 3 nthi ed

d. W at is th ercent com sition o I ydrog iithe nple’

4. One source of aluminum metal is alumina, A1203.

52.9% a. Determine the percentage composition of Al in alumina.

2100 th b. How many pounds of aluminum can be extracted from 2.0 tons ofalumina?

5. Compound A has a molar mass of 20 g/mol, and compound B has a molar mass of 30 g/moi.

20 9 a. What is the mass of 1.0 mol of compound A. in grams?

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

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

58 CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS MODERN CHEM[STRY(op:.rht r h i-Lit Rm&iati Vt nsn AU rtgL reered

CHAPTER 7 REVIEW Ihemica Formulas ard Chemical C pou d

SECTION 4

SHORT ANSWER Answer the foflowing questions in the space provided.

1. Write empirical formulas to match the following molecular formulas:

— N205 b \O

_____

HgC c.

CH2 d. C6H12

2. C4H8 A certain hydrocarbon has an empirical formula of C’H and a molarmass of 56.12 g/mol. What is its molecular formula?

3. A certain ionic compound is found to contain 0.012 mol of sodium 0.012 rr ol of sulfur, and0.018 mol of oxygen.

Na25203 a. What is its empirical formula?

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

PROBLEMS Write the answer on the tine to the ‘eft. Show aH your work in the spaceprovided.

4. Water of hydration was discussed in Sample Problem K on pages 243244 f the text Strongheating will drive off the water as a vapor in hydrated copper(H) sulfate. Use the data table belowto answer the following’

Mass of the empty crucible 4.00 g

Mass of the crucible plus hydrate sample 4.50 gMass of the system after heating 4.32 gMass of the system after a second heating 4.32 g

36% a. Determine the mass percentage of water in the origmal sample.

MODERN CHEMISTRY CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS 590 H R ar’ nd ghr re

SEC IO14 u

c Wh tmgh bc hc uposeofth sec rdhe rig

The second heat! stnsure that aN the water in the sapas been driven off.

If the mass is less after the second heating water was still present after the first

5. Gas X as found to be 24 0% carbon and 76M% fluorine by mass.

CF2 a. Determine the empirical formula of gas X

C4F8 b. Given that the molar mass of gas X is 20001 g/mol, detern inc itsmolecular formula.

6. A compound is found to contain 43 2% copper, 24 1% chlorine, and 317% oxygen by mass.

CuCIO3 a. Determine its empirical formula

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

copper(l) chlorate

_______________

60 CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS

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MODERN CHEMISTRY‘ H Re r

[CIPIWrER 7REVItW

Chemical Formulas and chemical compounds

SHORT ANSWER Answer the fo lowing questions in the pace provided.

1 V i formu as for th foil vii u cor ( ds,

_____CuCO3

a pc II) arbonaL

NSO3 b odiu i sulfltG

JNH4)3P04 c. a nmoniu vi phosphate

_____________

d. n(IV sulfide

HNO2 e. nitrous acid

2. \\ rite the Stock system names for the foi1owng compounds:

magnesium perchorate a, Mg(C1O4)-

iron(II) nitrate b. FeNO1)2

iron(HI) nitrite c. Fe(NO2)

cobaft(II) oxide d CoO

nitrogen(V) oxidee. dinitrogen pntoxidc

3, — 13 atoms a. many atoms are reprecntrd h the formuL Ci(HSfl42?

—

mol b. How many moles of oxygen atoms are in a O5O mol sar p e of thcompound9

+6 c Assign the oxidation number to sulfur in the HSO anion.

4. Assign the oxidation number to the element specified in each of the foIIoing:

______

a. hydrogen in HO-

_____

b. hydrogen in MgJ-I

0 c. sulfur in S

4 d. carbon in (CO)1

e. chromium in Na2Cr)07

f. nitrogen in NO2

MODERN CHEMISTRY — CHEMICAL FORMULAS AND CHEM CACOVPOUNDS 61C p r S H i a nst r

PROB EM V r t i ho l-o aN u vo k m [srac o

d f ic sir nass

1) mo1cuIe of C Hd .X 0 Ieculs of ( H 02

6.

_________

a. What is the formula for sodium hydroxide?

40.00 g/mol b What is the formula mass of sodium hydroxide

________

c What is the mass in grams of 0 25 mol of sodium hydroxide

_80% C, 20 H What is the percertage composition of ethanc gas. C,H6 to the nearestwhole r umber

8. Ribose is an important sugar (part of RNA),with a molar mass of150,15 g/mol. If its empirical formula is CH2O. what is its molecularformula’?

62 CHEMICAL FORMULAS AND_CHEMAL COMPOUNDS

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MODERN CHEMTRYC S I R d W nsto nhts re e

Na

MIXED RE IEW continued

9. Butce gas, CJ{. 1 otten used e a tuel.

______________ __________

a. Vs hlat i the ma’ u crams ut ol biiranc

18 Y 1024 moecules b F ov nans molecules arc p s t that .00 mol sa

C2H5 Wf at is the empirical forr ula of the ga ?

io. C10H8 Naphthalene is a soft covalent solid that is often used in mothballs. Itsmolar mass is 128.18 g!mol and it contains 93.75 carbon and 6.25C/chydrogen. Determine the molecular formula of napthaiene from thisinformation.

11. N cotine has the formula C H5Nz. To determine its composition, a sample ‘s burned in excessoxygen, producing the following results:

1.0 mol of CO20.70 mol of H200.20 mol of NO2

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

1.Omo

_______

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

MODERN CHEMISTRY

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CHEMICAL FORMULAS AND CHEMICAL COMPOUNDS 63C sri t 5 1 5 C r W Jstcst I h e C.

—20o cte tl urn ii f itr gcr o hr.

co bus or p d cts

_____

17N d Detcrmine thc empirical formula of ucotine fasd )r yourcalculations.

162 g/moi e. In a separate experiment, the molar mass of nicotine is found to besomewhere between 150 and 180 g/mol Calculatr the molar massof nicotine to tie nearest gram

12. When MgCO3(jis strongly heated it produces solid MgO dS gaseous CO2 i driven off.

___________ _____ ______________

a. What is the percentage loss in mass as thisreaction occurs

Mg is +2,Cis +4, and 0 is 2— h, Assign the oxidation number to each atom in MgCO3.

No

________

c Does the oxidation number of c rbon change upon theformation of C02?

64 CHEMCAL FORMULAS AND CHEMICAL COMPOUNDS MODERN CHEMISTRYC yrg I R icFr rd r o / g t s r d