Name:    Unit 6 Practice Test - No Molarity

True/False
Indicate whether the statement is true or false.

1.

Avogadro’s number refers to the number of particles in one gram of a substance.

2.

One mole of a substance has the same volume as one mole of any other substance, regardless of what substances are being compared.

3.

One mole of a substance has the same number of particles as one mole of any other substance, regardless of what substances are being compared.

4.

To find the percent by mass of a compound if you are given the formula, divide the molar mass of that element in one mole of the compound by the total molar mass of the compound.

5.

The empirical formula for a compound consists of the symbols for the elements in the compound without any subscripts.

6.

The percent by mass of each element in a compound is known as the percent composition of a compound.

7.

The formula for carbon dioxide, CO2, can represent
 a. one molecule of carbon dioxide. b. 1 mol of carbon dioxide molecules. c. the combination of 1 atom of carbon and 2 atoms of oxygen. d. all of the above.

8.

What is the formula mass of ethyl alcohol, C2H5OH?
 a. 30.33 amu b. 33.27 amu c. 45.06 amu d. 46.08 amu

9.

The molar mass of NO2 is 46.01 g/mol. How many moles of NO2 are present in 114.95 g?
 a. 0.4003 mol b. 1.000 mol c. 2.498 mol d. 114.95 mol

10.

The molar mass of CCl4 is 153.81 g/mol. How many grams of CCl4 are needed to have 5.000 mol?
 a. 5 g b. 30.76 g c. 769.0 g d. 796.05 g

11.

The molar mass of H2O is 18.02 g/mol. How many grams of H2O are present in 0.20 mol?
 a. 0.2 g b. 3.6 g c. 35.9 g d. 89.9 g

12.

The molar mass of NH3 is 17.03 g/mol. How many moles of NH3 are present in 107.1 g?
 a. 0.1623 mol b. 3.614 mol c. 6.289 mol d. 107.1 mol

13.

How many oxygen atoms are there in 0.500 mol of CO2?
 a. 6.02 1023 b. 3.01 1023 c. 15.9994 d. 11

14.

How many molecules are there in 5.0 g of methyl alcohol, CH3OH?
 a. 9.4 1022 b. 3.0 1024 c. 3.6 1024 d. 3.8 1024

15.

What is the percentage composition of CF4?
 a. 20% C, 80% F c. 16.8% C, 83.2% F b. 13.6% C, 86.4% F d. 81% C, 19% F

16.

What is the percentage composition of CO?
 a. 50% C, 50% O c. 25% C, 75% O b. 12% C, 88% O d. 43% C, 57% O

17.

The percentage composition of sulfur in SO2 is about 50%. What is the percentage of oxygen in this compound?
 a. 25% b. 50% c. 75% d. 90%

18.

A formula that shows the simplest whole-number ratio of the atoms in a compound is the
 a. molecular formula. c. experimental formula. b. ideal formula. d. empirical formula.

19.

What is the empirical formula for a compound that is 31.9% potassium, 28.9% chlorine, and 39.2% oxygen?
 a. KClO2 b. KClO3 c. K2Cl2O3 d. K2Cl2O5

20.

What is the empirical formula for a compound that is 43.6% phosphorus and 56.4% oxygen?
 a. P3O7 b. PO3 c. P2O3 d. P2O5

21.

A compound contains 259.2 g of F and 40.8 g of C. What is the empirical formula for this compound?
 a. CF4 b. C4F c. CF d. CF2

22.

A compound contains 64 g of O and 8 g of H. What is the empirical formula for this compound?
 a. H2O b. H2O2 c. HO2 d. HO

23.

A molecular compound has the empirical formula XY3. Which of the following is a possible molecular formula?
 a. X2Y3 b. XY4 c. X2Y5 d. X2Y6

24.

A compound's empirical formula is C2H5. If the formula mass is 58 amu, what is the molecular formula?
 a. C3H6 b. C4H10 c. C5H8 d. C5H15

25.

A compound's empirical formula is N2O5. If the formula mass is 108 amu, what is the molecular formula?
 a. N2O5 b. N4O10 c. NO3 d. N2O4

26.

A compound's empirical formula is CH. If the formula mass is 26 amu, what is the molecular formula?
 a. C2H2 b. CH3 c. CH4 d. C4H

27.

What is the mass percentage of chlorine in NaCl?
 a. 35.45% c. 60.7% b. 50% d. 64.5%

28.

To find the molecular formula from the empirical formula, one must determine the compound's
 a. density. c. structural formula. b. formula mass. d. crystal lattice.

29.

A compound's empirical formula is CH3. If the formula mass is 30 amu, what is the molecular formula?
 a. CH3 c. C2H6 b. CH4 d. C3H9

30.

How many grams of phosphorus are in 500.0 grams of calcium phosphorus?
 a. 49.92 grams c. 310.2 grams b. 99.84 grams d. 130.1 grams

31.

Calculate the number of molecules in 4.0 mol H2O.
 a. 0.60 ´ 1023 molecules c. 2.4 ´ 10–23 molecules b. 2.4 ´ 1024 molecules d. 2.4 ´ 1023 molecules

32.

Which of the following elements exists as a diatomic molecule?
 a. neon c. nitrogen b. lithium d. sulfur

33.

All of the following are equal to Avogadro's number EXCEPT ____.
 a. the number of atoms of bromine in 1 mol Br b. the number of atoms of gold in 1 mol Au c. the number of molecules of nitrogen in 1 mol N d. the number of molecules of carbon monoxide in 1 mol CO

34.

Which of the following compounds has the highest oxygen content, by weight?
 a. NaO c. BaO b. CO d. HO

35.

What is true about the molar mass of chlorine gas?
 a. The molar mass is 35.5 g. b. The molar mass is 71.0 g. c. The molar mass is equal to the mass of one mole of chlorine atoms. d. none of the above

36.

What is the number of moles of beryllium atoms in 36 g of Be?
 a. 0.25 mol c. 45.0 mol b. 4.0 mol d. 320 mol

37.

The volume of one mole of a substance is 22.4 L at STP for all ____.
 a. gases c. solids b. liquids d. compounds

38.

What is the number of moles in 500 L of He gas at STP?
 a. 0.05 mol c. 22 mol b. 0.2 mol d. 90 mol

39.

Given 1.00 mole of each of the following gases at STP, which gas would have the greatest volume?
 a. He c. SO b. O d. All would have the same volume.

40.

The lowest whole-number ratio of the elements in a compound is called the ____.
 a. empirical formula c. binary formula b. molecular formula d. representative formula

41.

What is the percent composition of carbon, in heptane, CH?
 a. 12% c. 68% b. 19% d. 84%

42.

Which of the following is NOT an empirical formula?
 a. CNH c. BeCrO b. CHO d. SbS

43.

What is the empirical formula of a compound that is 40% sulfur and 60% oxygen by weight?
 a. SO c. SO b. SO d. SO

44.

How many moles of tungsten atoms are in 4.8 10 atoms of tungsten?
 a. 8.0 10 moles c. 1.3 10 moles b. 8.0 10 moles d. 1.3 10 moles

45.

Which of the following is NOT true about empirical and molecular formulas?
 a. The molecular formula of a compound can be the same as its empirical formula. b. The molecular formula of a compound can be some whole-number multiple of its empirical formula. c. Several compounds can have the same empirical formula, but have different molecular formulas. d. The empirical formula of a compound can be triple its molecular formula.