Chemical Engineering Chapter 9 Analysis of a sample of a compound shows that

51) Which of the following is the correct “set-up” for the problem “How many moles of C are

present in 25.00 grams of C6H12O6?”

A)

B)

C)

D)

52) The “set-up” for the problem “How many oxygen atoms are there in 4.0 moles of N2O4”

which follows is correct, except for the use of letters rather than numbers in the conversion

factors. What are the correct numerical values of A and D respectively?

A) 4 and 4

B) 1 and 4

C) 4 and 1

D) 4 and 6.02 x 1023

53) Which of the following is the correct “set-up” for the problem “How many grams of S are

present in 50.0 g of S4N4?”

A)

B)

C)

D)

54) The number of moles of O atoms in 27 g of OF2 is ________.

A) 13 moles

B) 6.4 moles

C) 0.50 moles

D) 0.20 moles

55) How many atoms of H are present in 27.6 g of NH3?

A) 2.93 x 1024 atoms

B) 3.67 x 1023 atoms

C) 9.79 x 1024 atoms

D) 3.55 x 1026 atoms

56) How many atoms are present in 0.65 moles of P4O10?

A) 8.7 x 1024 atoms

B) 2.5 x 1024 atoms

C) 2.5 x 1025 atoms

D) 5.5 x 1024 atoms

57) Calculate the number of potassium ions present in a 16.42 gram sample of K3P.

A) 2.931 x 1024 potassium ions

B) 2.001 x 1023 potassium ions

C) 1.466 x 1024 potassium ions

D) 2.474 x 1023 potassium ions

58) How many carbon atoms are there in 25.0 grams of Al2(CO3)3?

A) 5.96 x 1024 atoms

B) 4.23 x 1022 atoms

C) 7.08 x 1025 atoms

D) 1.93 x 1023 atoms

59) What is the percent purity by mass of a 55.6 g sample of Fe2O3 in which there are 4.56 g of

impurities?

A) 8.20%

B) 91.8%

C) 9.82%

D) 4.56%

60) What is the mass of the impurities in a 35.7 g sample of NaHCO3 that is 88.9% pure?

A) 3.96 g

B) 31.7 g

C) 27.8 g

D) 4.28 g

61) What is the mass, in grams, present of the pure NaHCO3 in a 35.7 g sample of NaHCO3 that

is 88.9% pure?

A) 3.96 g

B) 31.7 g

C) 27.6 g

D) 4.49 g

62) Which of the following is the empirical formula for the compound C2H4O2?

A) C3H6O3

B) CH2O

C) CHO

D) C2HO

63) The empirical formula of C10H20 is:

A) C10H20

B) C5H10

C) C2H4

D) CH2

64) What is the empirical formula of a compound that contains 78.11% B and 21.89% H?

A) BH2

B) BH3

C) B2H6

D) B2H3

65) Analysis of a sample of a compound shows that 0.130 moles of Cl, 0.130 moles of H and

0.520 mole of O are present. What is the empirical formula of the compound?

A) HClO

B) HClO2

C) HClO3

D) HClO4

66) Analysis of an unknown nickel oxide compound indicated that the molar ratio of nickel to

oxygen was 0.167 to 0.251, respectively. What is the empirical formula for the compound?

A) Ni3O4

B) NiO

C) NiO3

D) Ni2O3

67) A sample of an ionic compound was analyzed and found to contain 6.072 g of sodium, 8.474

g of sulfur, and 6.336 g of oxygen. What is its empirical formula?

A) NaSO3

B) Na2SO3

C) Na2S2O3

D) Na2SO4

68) If a 1.59 gram sample of a carbon-containing compound is burned in air, 1.01 gram of CO2

is produced. What is the percent carbon in the compound?

A) 29.3%

B) 17.4%

C) 55.7%

D) 92.1%

69) What is the molecular formula of a compound that contains 40.0% C, 6.71% H, and 53.29%

O? The molecular mass of this compound is 60.05 g/mol.

A) C2H4O2

B) CH2O

C) C2H3O4

D) C2H2O4

70) The empirical formula of a compound is CH2O and its molecular mass is 120.12 amu. What

is the molecular formula?

A) C2H4O2

B) C3H6O3

C) C4H8O4

D) C5H10O5

71) Analysis of an unknown sample indicated the sample contained 0.140 grams of N and 0.320

grams of O. The molecular mass of the compound was determined to be 92.02 amu. What is the

molecular formula of the compound?

A) NO

B) N2O

C) N2O4

D) NO2

72) Carbohydrates have an empirical formula of CH2O. What is the molecular formula of the

sugar glucose if it has a molecular mass of 180.18 amu?

A) C3H6O3

B) C4H8O4

C) C5H10O5

D) C6H12O6

73) Octane is a principle component of gasoline. The empirical formula of octane is C4H9, and

the molar mass of octane is 114.26 grams per mole. What is the molecular formula of octane?

A) C4H9

B) C8H36

C) C12H27

D) C8H18

74) The empirical formula of a compound was determined to be P2O3. The molecular weight of

the compound is 220 g/mol. What is the molecular formula of the compound?

A) P2O3

B) P4O6

C) P2O5

D) P4O10

9.2 Short Answer

1) Determine the percentage composition for all elements in the compound C10H14N2.

2) Match the statements on the left with an appropriate response from the right. Responses on the

right may be used more than once or need not be used at all.

A) ________ has a mass of 4.0 grams

1) 1/4 mole CH4

B) ________ contains 1.20 x 1024 molecules

2) 1/4 mole NH3

C) ________ contains 1 mole of atoms

3) 2 moles H2O

D) ________ contains 4 moles of H atoms

4) 1/2 mole N2H

3) Contrast the two members of each pair in the statements on the left, and then select your

response from the response list on the right.

A) ________(I) formula mass of CBr4

1) I is greater than II

(II) formula mass of P2S3

2) I is less than II

3) I is equal to II

B) ________(I) grams in 1 mole of SiF4

(II) grams in 1 mole of AsF3

C) ________(I) moles in 50 grams of N2

(II) moles in 50 grams of H2S

D) ________(I) molecules in 3 moles of SO2

(II) molecules in 3 moles of SO3

E) ________(I) atoms in 2 moles of NO2

(II) atoms in 2 moles of N2O

F) ________(I) molecules in 28 grams of Cl2

(II) molecules in 28 grams of NaCl

G) ________(I) moles of N atoms in 34 g NH3

(II) moles of N atoms in 28 g of N2

H) ________(I) moles of O atoms in Avogadro’s number of SO2 molecules

(II) moles of O atoms in twice Avogadro’s number of CO molecule

22

4) How many atoms are present in a Mg sample with a mass of 10.6 grams?

5) What is the mass, in grams, of a single V atom?

6) A sample of 15.5 g of caffeine, C8H10N4O2, was extracted from some fresh coffee. How

many nitrogen atoms does this sample contain?

7) The characteristic odor of pineapple is due to ethyl butyrate, C6H12O2. A sample of 15.5 g of

ethyl butyrate was extracted from some fresh pineapple. How many carbon atoms were obtained

from this extraction?

8) How many grams of Cl are present in a 26.0 gram sample of P3N3Cl6?

9) How many moles of S are present in a sample containing 8.3 x1024 molecules of S4N4?

10) Butane, C4H10, is used as lighter fluid. What mass of butane contains the same mass of

carbon as 50.0 g of BaCO3?

11) Determine the empirical formula for a compound, a sample of which contains 1.94 x 1024

atoms C, 6.43 moles of H, and 51.5 g O.

12) What is the empirical formula for a compound having the following percentage composition:

51.3% calcium and 48.7% fluorine?

13) Analysis of a sample of a compound indicated that 1.286 grams of nitrogen and 2.204 grams

of oxygen were present. What is the empirical formula of the compound?

14) Upon analysis, a compound having a molar mass of 144 gram/mol is found to contain 66.6%

C, 11.2% H and 22.2% O. What is the molecular formula of the compound?

15) A sample of a compound contained 0.4364 grams of phosphorus and 0.5636 grams of

oxygen. The molar mass of the compound was determined to be 238.88 gram/mol. What is the

molecular formula of the compound?

16) Determine the empirical and molecular formulas for caffeine, a stimulant found in coffee and

soda, given the following percent composition: 49.5% carbon, 5.15% hydrogen, 28.9% nitrogen,

and 16.5% oxygen. The molecular weight of this compound is approximately 195 g/mol.