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# CHEM 101-Introductory Chemistry I-EXAM 1CHAPTERS 2, 3, 4 and 5

CHAPTER 2

1. A piece of plastic weighing 1.157 g has a volume of 1.48 cm3. A piece of wood has the same volume but weighs 3.85 g. The density of liquid X is 0.765 g/mL and the density of liquid Z is 1.13 g/mL. The two liquids are immiscible. If the plastic and wood are added to the two liquids, what is the order of layers from top to bottom in the container?

b. liquid X, plastic, liquid Z, wood

2. A sample of hard plastic, mass of 25.00 grams, floats when you put it in water. If we wanted to determine the density of the ball by using the displacement of a liquid to determine its volume which of the following liquids might we choose?

a. Water

3. A rectangular piece of tin foil has a mass of 571 milligrams and measures 5.1 cm by 10.25 centimeters. What is the thickness of foil given the density of tin is 7.28 g/cm3?

a. 0.0015 cm

Chemistry 101 Spring 2020

4. An empty flask has a mass of 79.31 grams. A 25.0 mL sample of an unknown liquid was pipetted into the flask and gave a total mass (flask plus liquid) of 97.010 grams. What is the density of the unknown liquid?

density = mass of liquid / volume of liquid

= (97.01-79.31)/25

= 0.708 gm/ml

5. What is the mass in grams of a 2.00 L volume of carbon tetrachloride (CCl4, density = 1.60 g/mL)?

density of CCl4 = 1.6 g/ml

Volume of CCl4 = 2Lit = 2000ml

mass of CCl4 = density * volume

= 1.60 g/ml * 2000 ml

= 3200 g

= 3.2 kg

6. The American Heart Association recommends that for every 1000 dietary calories consumed, the sodium intake should be 1000 mg or less and should not exceed a daily limit of 3300 mg for an adult. What is the yearly limit on sodium intake in pounds?

b. 2.7 lb

7. A mass of mercury occupies 0.950 L. What volume would an equal mass of ethanol occupy? The density of mercury is 13.546 g/mL and the density of ethanol is 0.789 g/mL.

c. 16.3 L

8. The density of aluminum is 2.702 g/cm3. What is the final liquid level of water if 1.130 ounces of aluminum is dropped into a graduated cylinder containing 15.90 mL of water?

c. 27.76 mL

9. When the mathematical operation is carried out, how many significant figures should be reported in the answer?

d. 4

10. Calculate the volume in milliliters of a sample of glycerine that has a mass of 0.150 kilograms. The density of glycerine is 1.26 g/cm3.

density = mass/volume in g/ml

mass = 0.150 × 1000 = 150 g

volume = mass/density

= 150/1.26

= 119.04 ml

CHAPTER 3

11. Which of the following is an example of matter?

c. helium in a balloon

12. Which of the following does not apply to a chemical compound?

d. Compounds can be separated into their constituent elements using only physical methods.

13. Which of the following pairs of substances are compounds?

b. KBr, CO

14. Which of the following does NOT involve a chemical change?

d. the melting of a piece of gold

15. Given the following combinations:

a. a homogeneous liquid mixture of bromine, Br2, and carbon tetrachloride, CCl4

b. a heterogeneous mixture of sand and silver

c. a homogeneous liquid mixture of benzene and octane, both hydrocarbons

d. a layer of octane floating on a layer of water

e. a gaseous mixture of helium, He, and argon, Ar

FOR TWO POINTS EACH circle the letter of the combination that fits the following definitions. Please note that there are five definitions and five combinations. This means that there is one AND ONLY ONE correct letter for each of the definitions. This is worth 10.

Which of the pairs is a solution of two elements?

(e)

Which of the pairs is a solution of an element and a compound?

(a)

Which of the pairs is an undissolved mixture of two compounds

(d)

Which of the pairs is a solution of two compounds?

(c)

Which of the pairs is an undissolved mixture of an element and a compound?

(b)

16. The relative inertness of neon is an example of the following?

b. chemical property

17. A mixture of gasoline and air exploding is an example of which of the following?

b. chemical property

18. Which of the following is the lowest temperature?

a. 84o C

19. Which of the following is a physical property of the chemical element cesium (Cs)?

e. turns to a silvery white liquid at 28 oC

20. A sample of matter described as “a colorless gas that cannot be separated into simpler substances using physical means and that reacts with copper to produce both a copper-nitrogen compound and a copper-oxygen compound” is a(n)

b. compound

21. Which of these materials will require the greatest amount of energy to warm from 30o C to 40o C

a. ethanol

22. I didn’t like the last calibration that we did on the quiz so this time when I calibrated my thermometer and used the Hankie scale (oH) I changed the calibration points. I assigned the boiling point of water as 200 oH and the freezing point of water as –200 oH. What is a temperature of 35 oC equivalent to on the Hankie scale now?

(H-(-200))/400=(c-0)/100=(F-32)/180=(K-273)/100

(H+200)/400=(C-0)/100

H=-60

23. Calculate the mass of water in grams that can be heated from 0 oC to 15 oC by the amount of heat evolved from cooling 1.00 kg of water from 100 oC to 25 oC.

1kg=1000g

q=1000*4.185*(100-25)=313875J

M=313875/2.05*15=10207.3g of water

24. Calculate the mass of copper in grams used if 210.0 J of heat is absorbed when copper is heated from 25.0 oC to 65.0 oC. Specific Heat of copper is 0.385 J/(g x oC).

210 = m*0.385*(65-25)

210 = m*15.4

m = 210/15.4 = 13.64g

The mass of copper = 13.64g

25. Find the specific heat of an unknown metal if a 35.5 gram sample at 99.6 oC produced a resulting temperature of 26.1 oC when placed in a calorimeter containing 100.5 grams of water at 20.2 oC.

35.54*C*(26.1-99.6)=-100.5*4.18*(26.1-

26. Metallic mercury (Hg) reacts with oxygen (O2) in air when heated to form dark red brown mercury(II) oxide (HgO). If 2.017 grams of mercury is completely converted into 2.178 grams of mercury(II) oxide, how many milligrams of oxygen was combined with the mercury in the process?

a. 161 mg

27. A 43 g serving of a chocolate candy has 2.10 x 102 Calories. Convert this energy to units of joules.

a. 879 J

28. What was the initial temperature of a 15.0 g sample of iron if adding 524 J of heat resulted in a final temperature of 100.0°C? The specific heat of iron is 0.448 J/(g°C).

524=15*0.488(100-T)

77.98=100-T

T=22C

29. An object starts at 85 oC, energy is added until the temperature increase to 100. oC for a total temperature change of 15 oC. What is the temperature change as expressed in degrees Fahrenheit?

d. 59 oF

30. What’s the final temperature in kelvin of 1.50 gallons of water with an initial temperature of 50oF if you add 432 kJ to the water?

(432*10^3)/(4838.4*4.186)=21.33C

50F=283.15K

283.15+21.33=304.48K

31. A small candy bar has 52.0 Calories. If all the energy is converted to heat by how much would it raise the temperature of 1.00 L of water?

b. 52.0 oC

32. If the temperature of water in a freezer decreases from 22°C to -25°C, what is the decrease in temperature in units of degrees Celsius and Kelvin?

c. 47°C, 47 K

33. Indium has a specific heat of 0.0568 cal/(g x oC). How many calories of heat energy are required to heat 0.9652 grams of indium from 68 oF to 311.0 oF?

d. 7.4 cal

CHAPTER 4

34. Arrange the five atoms – 42Ca, 39K, 44Sc, 37Ar and 43Ti in order of

INCREASING MASS (SMALLEST MASS FIRST)

Ar < K < Ca < Ti < Sc

INCREASING NUMBER OF ELECTRONS (SMALLEST NUMBER OF ELECTRONS FIRST)

Ar < K < Ca < Sc < Ti

DECREASING NUMBER OF NEUTRONS (LARGEST NUMBER OF NEUTRONS FIRST)

Ti < Sc < Ca < K < Ar

DECREASING NUMBER OF PROTONS (LARGEST NUMBER OF PROTONS FIRST)

Sr > Ca > Ti > K > Ar

35. Which of the following two atoms are isotopes?

b. and

36. What is the identity of element Q if the ion Q2+ contains 10 electrons?

d. Mg

37. Consider particle A with a mass number of 62, atomic number 32 and an ionic charge of +2. Which of the following is correct

c. A has an equal number of neutrons and electrons

38. Atom A has 5 protons and 6 neutrons; atom B has 6 protons and 5 neutrons. These atoms are

a. isotopes

39. In the gold foil experiment, Rutherford used alpha particles He2+ (mass number 4) to bombard a gold foil. An alpha particle is simply a helium atom that has lost two electrons to give it a +2 charge. Which of the following is FALSE about an alpha particle?

An alpha particle has four neutrons in its nucleus

40. Fill in the following table. This is worth 8 points – one point for each correct row.

Symbol

Z

A

Number of Protons

Number of Neutrons

Number of Electrons

Charge

Fe2+

26

54

26

28

24

2+

Ag

47

107

47

60

47

0

Ti

22

49

22

27

18

14

Ba+2

56

137

56

81

54

2+

O2-

8

16

8

8

10

-2

Ca

20

44

20

24

20

0

Br-

35

79

35

44

36

1-

Kr

36

80

36

44

36

0

41. Calculate the atomic mass for the unknown element hankie given the following data for its natural isotopes:

58Ha 57.933 amu 0.33%

57Ha 56.935 amu 2.19%

56Ha 55.935 amu 91.66%

54Ha 53.940 amu 5.82%

(57.933*0.033)+(56.935*0.0219)+(55.935*0.9166)+(53.94*0.0582)

=55.8473844

=55.847amu

42. Rhenium has two naturally occurring isotopes: Re-185 with a natural abundance of 37.40% and Re-187 with a natural abundance of 62.60%. The sum of the masses of the two isotopes is 371.9087 amu. Find the masses of the individual isotopes.

Re-185: (0.3740)(x) = 0.3740x

Re-187: (0.6260)(371.9087 - x) = 232.8148462 - 0.6260x

0.3740x + 232.8148462 - 0.6260x = 186.207

0.3740x + 232.8148462 - 0.6260x - 232.8148462 = 186.207 -232.8148462

0.3740x - 0.6260x = -46.6078462

-0.2520x = -46.6078462

-0.2520x/-0.2520x = -46.6078462/-0.2520

x = 184.9517706 amu = 184.952

The atomic weight o Re-185: 184.952 amu

The atomic weight of Re-187 is: 371.9087 minus 184.952 = 186.957 amu

43. Among the main group elements in the periodic table the more metallic ones are more likely to be found

a. toward the left and down

44. Give an element name and symbol as an example of each of the following (Only one element is necessary for each category):

a. an alkali metal Lithium

b. an alkaline earth metal Beryllium

c. a halogen Fluorine

d. a noble gas Neon

e. a representative element in the fifth period Rubidium

f. a transition element in the fifth period Silver

g. a metalloid Boron

h. a nonmetal left of the metalloids Germanium

i. six valence electrons Neon

j. an element in the fifth period that gains electrons when it undergoes chemical changes Zirconium

CHAPTER 5

45. Write the FORMULA AND NAME THE COMPOUND that results from the following combinations of different elements. Assume that the first element in the combination comes first in the formula. Carbon dioxide is provided as an example. This is worth 10 points.

ELEMENT

NUMBER OF ATOMS

ELEMENT

NUMBER OF ATOMS

FORMULA

NAME

CARBON

1

OXYGEN

2