1. Chemical Formulas and Chemical Compounds
Chapter 7 Review – Answers

2. Pages
In a stock name such as iron(III) sulfate, the roman number tells us ____.
The result of changing a subscript in a correctly written chemical formula is to _____.
C. The charge on each Fe ion
C. Change the formula so that it no longer represents the compound it previously represented.

3. Pages 53 - 54 4 elements 6 oxygen atoms 21 atoms
The explosive TNT has the molecular formula C7H5(NO2)3.
How many elements make up this compound?
How many oxygen atoms are present in one molecule of C7H5(NO2)3?
How many atoms in total are present in one molecule of C7H5(NO2)3?
How many atoms are present in a sample of 2  molecules of C7H5(NO2)3?
4 elements
6 oxygen atoms
21 atoms

4. Pages
How many atoms are present in each of these formula units?
Ca(HCO3)2
C12H22O11
Fe(ClO2)3
Fe(ClO3)2
11 atoms
45 atoms
10 atoms
9 atoms

5. Pages 53 - 54 (see below) N2O5 Carbon disulfide
What is the formula for the compound dinitrogen pentoxide?
What is the Stock name for the covalent compound CS2?
N2O5
Carbon disulfide

6. Pages
Some binary compounds are ionic, others are covalent. The types of bonding partially depend on the position of the elements in the periodic table. Label each of these claims as True or False; if False, specify the nature of the error.
Covalently bonded binary molecular compounds typically form from nonmetals.
True

7. Pages
Some binary compounds are ionic, others are covalent. The types of bonding partially depend on the position of the elements in the periodic table. Label each of these claims as True or False; if False, specify the nature of the error.
Binary ionic compound form from metals and nonmetals, typically from opposite sides of the periodic table.
True

8. Pages
Some binary compounds are ionic, others are covalent. The types of bonding partially depend on the position of the elements in the periodic table. Label each of these claims as True or False; if False, specify the nature of the error.
Binary compound involving metalloids are always ionic.
False; metalloids on the right of the stair-step line act as nonmetals in compounds

9. Pages 53 - 54 Al2S3 Al2(SO3)3 Lead(II) chloride
Fill in the blanks in the table below.
Compound Name
Formula
Aluminum sulfide
Aluminum sulfite
PbCl2
(NH4)3PO4
Al2S3
Al2(SO3)3
Lead(II) chloride
Ammonium phosphate

10. Pages
Tin has possible oxidation numbers of +2 and +4 and forms two known oxides. One of them has the formula SnO2.
Give the stock name for SnO2.
Give the empirical formula for the other oxide of tin.
Tin(IV) oxide
SnO

11. Pages
Scientists believe that two separate reactions contribute to the depletion of the ozone layer, O3. The first reaction involves oxides of nitrogen. The second involves free chlorine atoms. Both reactions follow. When a compound is not stated as a formula, write the correct formula in the blank beside its name.
_____(nitrogen monoxide) + O3 → ______ (nitrogen dioxide) + O2
Cl + O3 → ______ (chlorine monoxide) + O2 NO
NO2
ClO

12. Pages
Consider the covalent dinitrogen trioxide when answering the following:
What is the formula for dinitrogen trioxide?
N2O3

13. Pages
Label each of the following statements as True or False:
If the formula mass of one molecule is x amu, the molar mass is x g/mol.
Samples of two different chemicals with equal numbers of moles must have equal masses as well.
Samples of two different chemicals with equal numbers of moles must have equal numbers of molecules as well.
True
False
True

14. Pages
How many moles of each element are present in a 10.0 mol sample of Ca(NO3)2?
10.0 mol calcium
20.0 mol nitrogen
60.0 mol oxygen

15. Pages
Consider a sample of 10.0 g of the gaseous hydrocarbon C3H4 to answer the following questions.
How many moles are present in this sample?
How many molecules are present in the C3H4 sample?

16. Pages
Consider a sample of 10.0 g of the gaseous hydrocarbon C3H4 to answer the following questions.
How many carbon atoms are present in this sample?
What is the percentage composition of hydrogen in the sample?

17. Pages
The chief source of aluminum metal is the ore alumina, Al2O3.
Determine the percentage composition of Al in this ore.
How many pounds of aluminum can be extracted from 2.0 tons of alumina?

18. Pages
Compound A has a molar mass of 20 g/mol, and compound B has a molar mass of 30 g/mol.
What is the mass of 1.0 mol of compound A?
How many moles are present in 5.0 g of compound B?
How many moles of compound B are needed to have the same mass as 6.0 mol of compound A?
20 grams

19. Pages
Write empirical formulas to match the following molecular formulas:
C2H6O4
N2O5
Hg2Cl2
C6H12
CH3O2
N2O5
HgCl
CH2

20. Pages
A certain hydrocarbon has an empirical formula of CH2 and a molar mass of g/mol. What is its molecular formula?
C4H8

21. Pages
A certain ionic compound is found to contain mol of sodium, mol of sulfur, and mol of oxygen.
What is its empirical formula?
Is this compound a sulfate, sulfite, or neither?
Na2S2O3
neither

22. Pages
Gas X is found to be 24.0% carbon and 76.0% fluorine by mass.
Determine the empirical formula of gas X.
CF2

23. Pages
Gas X is found to be 24.0% carbon and 76.0% fluorine by mass.
Given that the molar mass of gas X is g/mol, determine its molecular formula.
C4F8

24. Pages
A compound is found to contain 43.2% copper, 24.1% chlorine and 32.7% oxygen by mass.
Determine its empirical formula.
CuClO3

25. Pages 59 - 60 Copper(I) chlorate
A compound is found to contain 43.2% copper, 24.1% chlorine and 32.7% oxygen by mass.
What is the correct Stock name of the compound in part a?
Copper(I) chlorate

26. Pages 61 - 64 Write formulas for the following compounds: CuCO3 Na2SO3
Copper(II) carbonate
Sodium sulfite
Ammonium phosphate
Tin(IV) sulfide
CuCO3
Na2SO3
(NH4)3PO4
SnS2

27. Pages 61 - 64 Write the Stock names for the following compounds:
Mg(ClO4)2
Fe(NO3)2
Fe(NO2)3
CoO
Magnesium perchlorate
Iron(II) nitrate
Iron(III) nitrite
Cobalt(II) oxide

28. Pages 61 - 64 (see below) 13 4 mol oxygen
How many atoms are representd by the formula Ca(HSO4)2?
How many moles of oxygen atoms are in a 0.50 mol sample of this compound? 13
4 mol oxygen

29. Pages
Following are samples of four different compounds. Arrange them in order of increasing mass, from smallest to largest.
25 g of oxygen gas
1.00 mol of H2O
3  1023 molecules of C2H6
2  1023 molecules of C2H6O2
c, b, d, a

30. Pages 61 - 64 (see below) NaOH 40 g/mol 10 grams
What is the formula for sodium hydroxide?
What is the formula mass of sodium hydroxide?
What is the mass in grams of 0.25 mol of sodium hydroxide?
NaOH
40 g/mol
10 grams

31. Pages
What is the percentage composition of ethane gas, C2H6, to the nearest whole number?
Ribose is an important sugar (part of RNA), with a molar mass of g/mol. If its empirical formula is CH2O, what is its molecular formula?
80% carbon, 20% hydrogen
C5H10O5

32. Pages 61 - 64 Butane gas, C4H10, is often used as a fuel. 174 grams
What is the mass in grams of 3.00 mol of butane?
How many molecules are present in that 3.00 mol sample?
What is the empirical formula of the gas?
174 grams
1.81  1024 molecules
C2H5

33. Pages
Napthalene is a soft covalent solid that is often used in mothballs. Its molar mass is g/mol and it contains % carbon and 6.25 % hydrogen. Determine the molecular formula of napthalene from this data.
C10H8

34. Pages
Nicotine has the formula CxHyNz. To determine its composition, a sample is burned in excess oxygen, producing the following results:
1.0 mol of CO2
0.70 mol of H2O
0.20 mol of NO2
Assume that all the atoms in nicotine are present as products.
Determine the number of moles of carbon present in the products of this combustion.
Determine the number of moles of hydrogen present in the products of this combustion.
Determine the number of moles of nitrogen present in the products of this combustion.
1.0 mol C
1.4 mol H
0.2 mol N

35. Pages
Nicotine has the formula CxHyNz. To determine its composition, a sample is burned in excess oxygen, producing the following results:
1.0 mol of CO2
0.70 mol of H2O
0.20 mol of NO2
Assume that all the atoms in nicotine are present as products.
Determine the empirical formula of nicotine based on your calculations.
In a separate experiment, the molar mass of nicotine is found to be somewhere between 150 and 180 g/mol. Calculate the molar mass of nicotine to the nearest gram.
C5H7N
162 g/mol