~-----------------------------------------------------------------------

Name _

UsingChemical Formulas

Class Date _

Sect~on7.3ReVIew •

4

3

1

2·

DIRECTIONS: Write on the line at the right of each statement the letter preceding the word or expression that bestcompletes the statement.

1. The molar mass of an element is the mass of one (a) atom of the element;

(b) liter of the element; (c) gram of the element; (d) mole of the element.

2. When the formula mass of a compound is expressed in grams, it is known as the(a) compound mass; (b) molar mass; (c) gram-atomic weight; (d) gram-ionic mass.

3. The sum of the atomic masses of all the atoms in a formula for a compound would mostproperly be called the (a) molecular mass; (b) formula mass; (c) atomic mass; (d) actual mass.

4. The term formula mass is a general term that can be applied to both ionic compounds andmolecular compounds because (a) ionic compounds exist as individual molecules; (b) molecularformulas are always empirical formulas; (c) not all formulas represent individual molecules;(d) molecular formulas are always Lewis formulas.

DIRECTIONS: Write the answer to questions 5-15 on the line to the right, and show your work in the spaceprovided.

5. The molar mass of N02 is 46.01 g. How many moles of NOz are present in 138.03 g? 5

6. The molar mass of CCl4 is 153.82 g. How many grams of CCl4 are needed to make 5.00 mol? 6

7. The molar mass of H20 is 18.02 g. How many grams of H20 are present in 0.20 mol? 7

8. The molar mass of LiF is 25.94 g. How many moles of LiF are present in 10.37 g? 8

9. How many moles of OH - ions are present in one mole of NaOH? 9

10. If one mole of H20 is separated into atoms, how many moles of H atoms are present? ____ 10

11. If two moles of ZnCIz separate into Zn + and Cl- ions, how many moles of Zn + ions arepresent? ____ 11

12. How many moles of NO; are present in one mole of Mg(N03)z? ____ 12

DIRECTIONS: Questions 13-15 refer to the following table. Round all answers to three significant figures.

____ 14

____ 13

____ 15

\\

TABLE OF ATOMIC MASSES

Element

SymbolAtomic

Mass (u)Hydrogen

H1.007 94

Oxygen

015;9994

Sodium

Na22.989 77

Chlorine

CI35.453

Calcium

Ca40.08

Using Chemical FormulasHRW material copyrighted under notice appearing earlier in this work.

13. What is the percent composition of oxygen inH2O?

14. What is the percent composition of chlorinein NaCI?

15. What is the percent composition of OH - inCa(OH)z?

Section 7.3 25

Name _

DeterminingChemical Formulas

Class Date _

Sec~on7.4RevIew •

2

7

4

6

8

5

3

1

DIRECTIONS: Write on the line at the right of each statement the letter preceding the word or expression that bestcompletes the statement.

1. A formula that shows the smallest whole-number ratio of the atoms in a compound is called

the (a) molecular formula; (b) ideal formula; (c) structural formula; (d) simplest formula.

2. A compound's simplest formula is also called its (a) empirical formula; (b) molecular formula;(c) structural formula; (d) Lewis formula.

3. The simplest formula is always the accepted formula for a(n) (a) atom; (b) molecule;(c) molecular compound; (d) ionic compound.

4. The simplest formula for a compound shows the symbols of the elements with subscriptsshowing the (a) actual numbers of atoms in a molecule; (b) number of moles of the compoundin 100 g; (c) smallest whole-number ratio of the atoms; (d) atomic masses of each element.

5. To determine the correct molecular formula from the simplest formula, one must determine

the compound's (a) density; (b) formula mass; (c) structural formula; (d) crystal lattice.

6. A molecular compound is found to have the simplest formula XY3. Which of the following isa possible molecular formula? (a) X2Y3 (b) XY4 (c) X2Y5 (d) X2Y6

7. The molecular formula for vitamin C is C6Hg06. The simplest formula is (a) CHO; (b) CH20;

(c) C3H403; (d) C2H402•

8. Among the following molecular formulas for hydrocarbons, the formula that is also thesimplest formula is (a) CH4; (b) C2H2; (c) C3H6; (d) C4HlO.

DIRECTIONS: Write the answer to questions 9-15 on the line to the right, and show your work in the spaceprovided. Questions 9-15 refer to the following table.

TABLE OF ATOMIC MASSES

Element

SymbolAtomic

Mass (u)Carbon

C12.0111

Oxygen

015.9994

Calcium

Ca40.08

Chlorine

CI35.453

Hydrogen

H1.007 94

Nitrogen

N14.00679. A compound contains 27.3 g of C and 72.7 g

of O. What is the simplest formula for thiscompound?

10. A compound is 36.1 % Ca and 63.9% Cl.What is the simplest formula for thiscompound?

11. A compound contains 64 g of 0 and 4 g of H.What is the simplest formula for this compound?

9

____ 10

____ 11

12. A compound is 82.4% Nand 17.6% H. What is the simplest formula for this compound? ____ 12

13. A compound's simplest formula is found to be HO. If the formula mass of the compound is34 u, what is the molecular formula? ____ 13

14. The simplest formula for a compound is determined to be CH3. If the formula mass is 30 u,what is the molecular formula? ____ 14

15. A compound is found to have the simplest formula N02. If the formula mass is 92 u, what isthe molecular formula? ____ 15

2& Section 7.4 Determining Chemical FormulasHRW material copyrighted under notice appearing earlier in this work.