1. Review Questions for 1st year chemistry

2. If gold has a density of 20 g/cm3, what is the mass of a cube of gold with sides of 2 cm?
Answer: A Use density = mass/volume
20 = mass/(2×2×2)
20 = mass/8
so mass = 160

3. 100. grams of water is heated from 30 degrees Celsius to 60 degrees Celsius, calculate the amount of energy added.
10,000 J
12,500 J
16,300 J
40 kJ
Answer: B
100 g x 4.18 x 30 = J

4. Balance the following equation:
__Al + __H3PO4  __AlPO4 + __H2
2,2,2,3
1,2,2,4
2,1,4,1
3,1,3,3
Answer: A
Balance H’s so both sides are 6
Balance PO4’s as a group
Then balance Al’s last

5. How many electrons are in the VALENCE shell of oxygen?16 10 8 6
Answer: D
Oxygen has 8 electrons total but
two of them are in the first shell of the
Bohr Model. The six remaining electrons
are found in the outer shell of the model.

6. Which of the following statements is true about the nucleus?
A. It is positively charged.
B. It contains only neutrons.
C. It is negatively charged.
D. It contains electrons and neutrons.
Answer: A
The nucleus has a positive charge because it contains positively charged protons to attract the electrons surrounding it.

7. What group on the periodic table contains elements that are very malleable, are good conductors, and are ductile?
Halogens
Alkaline-Earth Metals
Noble Gases
Metalloids
Answer: B
The structure of metals includes a sea of electrons which allows heat to more easily flow through the substance. It also allows metals to bend without breaking easily.

8. Which of the following statements is true?
The reaction presented by the graph is endothermic.
The reaction presented by the graph is exothermic.
The reaction above has a negative delta H.
The reaction above has a catalyst.
Answer: A
The reaction presented by the graph is endothermic because it is absorbing energy instead of releasing it, shown by the positive change in delta H (difference between products and reactants).

9. How many moles of O2 are in 64 grams of O2?
2.5 4
128 2
Answer: D
64 g O2 1 mol O2 = 2 mol O g O2

10. What is the formula mass of 𝐾 2 𝑆𝑖𝑂?
83.19 g/mol
g/mol
120 g/mol
g/mol
Answer: B
(39.098*2)+(28.085)+(16) =

11. If the wavelength of light is 5.8x10-7 m, what color is the light?
Yellow
Orange
Blue
Green
Answer: A
Check reference table page 8. Yellow is correct because the wavelength falls between 5.7x10-7 m and 5.9x10-7 m.

12. Which of the following changes would increase the pressure of a gas in a closed container?
Increased volume of container
Increased number of particles in the container
Decreased temperature
Decreased number of particles in the container
Answer: B
The more particles there are in a container, the more collisions that occur which raises the pressure.

13. Which element has the highest electronegativity?
Chlorine
Iodine
Fluorine
Bromine
Answer: C
Electronegativity decreases as you move down the periodic table because as you move down, there are more valence shells which shield the pull of the protons in the nucleus. Fluorine is the first element in its group and therefore has the highest electronegativity.

14. For an atom that is neutral, which of the following statements is FALSE?
The number of protons is equal to the number of neutrons.
The atomic number is equal to the number of protons.
The number of protons is equal to the number of electrons.
The atomic mass is equal to the sum of protons and neutrons in the atom.
Answer: A

15. Which of the following has the highest boiling point?
CO2
SO2 HF
Answer: D
An H-F bond is a type of hydrogen bond. This bond has a stronger intermolecular force, so it will have the higher boiling point.

16. The molecular geometric shape of H2S is: Bent Linear Trigonal Planar
Trigonal Pyramidal
Answer: A
Since the lone pairs want to repel each other, it causes the bond pairs to bend towards each other, causing the molecular form of the compound to be bent.

17. If an electron drops from the 6th energy level to the 2nd, what type of light is released?
Visible
Infra-red
Ultraviolet
X rays
Answer: A
Visible is correct because the wavelength of light released based on the Bohr model falls in the visible light range. Use page 8 of the reference tables.

18. Which image shows a representation of a compound?B C
None of the images
Answer: B
The molecules are made of two kinds of atoms bonded together. All particles are the same.

19. 19 grams of water are heated from ice at 0 degrees Celsius to 15 degrees Celsius, calculate the amount of energy added.
9,000 J
7,500 J
17 kJ
1,900 J
Answer: B
(19 x 4.18 x 15) + (19 x 334) =

20. What is the percent composition of hydrogen in ethylene glycol ( 𝐶 2 𝐻 6 𝑂 2 )?
1.62%
10.00%
4.87%
9.74%
Answer: D
(1.008 × 6)/ × 100 = 9.74%

21. What type of bonding is found between carbon and hydrogen in CH4?
Metallic
Covalent
Ionic
Answer: B
A bond between two nonmetals is covalent. Both Carbon and Hydrogen are nonmetals so the bond between them is Covalent.

22. The volume of a gas at 99. 0 kPa is 300 mL
The volume of a gas at 99.0 kPa is 300 mL. If the pressure increases to 188 kPa, what is the final volume?
569 mL
52.1 mL
158 mL
None of the above
Answer: C
Using Boyle’s Law P1V1=P2V2, to find the final volume × 300 = 188 × V2

23. What does T represent on the graph?
The products of the reaction.
The reverse activation energy.
The effects of a catalyst.
The heat of reaction.
Answer: D
T displays the energy absorbed during the reaction, which is the positive difference between Y (reactants) and X (products) in this case.

24. How many moles are in 25 grams of water?
Answer: B
25 g H2O 1 mol H2O = mol H2O g H2O

25. What type of reaction is this?
PbCl2 + AgNO3 —-> Pb(NO3)2 + AgCl
combustion
decomposition
synthesis
double replacement
Answer: D
Because two compounds traded ions.

26. Which element matches the following Bohr model?
A. Boron
B. Magnesium
C. Neon
D. Sodium
Answer: D
Sodium has 11 electrons and needs 3 electron shells. The Bohr model represents the electrons by the 11 dots.

27. As you move across the periodic table
Atomic radii increases
Atomic radii decreases
Atomic radii stay the same size
Answer: B
As you move across the periodic table, elements have more protons. Their increasingly stronger pull on the outer shell draws the outer shell closer to the nucleus, decreasing the size of the element.

28. Which of the following elements will NOT be surrounded by an octet of electrons in a correctly drawn Lewis structure?
Hydrogen
Oxygen
Chlorine
Carbon
Answer: A
The hydrogen atom only has one valence electron in the outermost shell. Its outer shell (its only shell) is the 1s orbital, which only needs two electrons.

29. 1s22s22p63s2 is what element?
magnesium
manganese
sodium
silicon
Answer: A
Magnesium has 12 electrons. It is located in the 3rd row, 2nd column.

30. An ice cube is placed in a cup of hot tea
An ice cube is placed in a cup of hot tea. What is the nature of the change that occurs?
The ice becomes liquid water, chemical change
The ice becomes tea, chemical change
The ice becomes liquid water, physical change
The ice becomes tea, physical change
Answer: C
Ice melting is a physical change from solid to liquid.

31. What is it called when a solid proceeds directly to the gas state skipping the liquid state?
Sublimation
Deposition
Vaporization
Freezing
Answer: A

32. What is the empirical formula of propanedinitrile (C8H4N2 ) ?
Answer: C
Simplify the subscripts. Empirical formula has the most simplified ratio.

33. At what temperature will 0. 654 moles of neon gas occupy 12. 30 L at 1
At what temperature will moles of neon gas occupy L at 1.95 atm?
447 K
18 K
273 K
None of the above
Answer: A
Using the ideal gas law, PV=nRT, T=PV/nR, plug in all the given information and solve for the temperature.
1.95 × = × × T

34. Different isotopes of an element have different numbers of _____________?
neutrons
protons
voltrons
electrons
Answer: A
Different numbers of neutrons result in different masses.

35. What is the molar mass of Ca3 N2 ?
g/mol
g/mol
54.09 g/mol
100.0 g/mol
Answer: B
( × 3) + (14.01 × 2) =

36. Which of the following does not form hydrogen bonds?
H2S
H2O
NH3 HF
 Answer: A
Hydrogen bonds can occur when a hydrogen atom is attracted to either a nitrogen atom, a fluorine atom, or an oxygen atom.

37. What does U represent on the graph?
The activation energy for the forward reaction.
The activation energy for the reverse reaction.
The heat of reaction.
The effect of a catalyst.
Answer: B
U represents the energy required to undergo the reverse reaction from X back to Y.

38. If an atom’s outermost electron is in a
d-orbital then the atom is a(n)
alkali metal.
alkaline-earth metal.
halogen.
transition metal.
Answer: D
Transition metal because only transition metals have an outermost electron in the d-orbital.

39. What happens to water as it boils?
The hydrogen and oxygen atoms separate and become gases.
The water molecules move slower.
Nothing
Hydrogen bonds between molecules break.
Answer: D
Water’s molecules remain intact, but bonds between molecules are weakened.

40. What is the point at which a substance coexists in solid, liquid, and gaseous forms?
equivalence point
equilibrium point
triple point
physical point
Answer: C

41. What kind of compound is Ca3N2?
Covalent
Ionic
Metallic
Other
Answer: B
It is composed of a metal and a nonmetal.

42. Which of the following is a part of Dalton’s Atomic Theory?
All matter is made up of atoms.
Atoms cannot be subdivided, created, or destroyed.
Atoms of different elements can combine in whole-number ratios to form chemical compounds.
All of the above
Answer: D
Dalton’s Atomic Theory states all of these.

43. The half-life of beryllium-14 is 4. 84 seconds
The half-life of beryllium-14 is 4.84 seconds. How much of a 16 gram sample of beryllium-14 is left after seconds?
4 g
8 g
20 g
2 g
Answer: D
14.52/4.84 = 3 half-lives
16/2/2/2 = 2 g (cut 16 in half 3 times)

44. Identify the correct products:
Na + CaF2 
NaF + Ca
Ca2F + Na
No reaction
NaF2 + Ca
Answer: C
Na is below Ca on the activity series. Always check the activity series for single replacement reactions.

45. What is FALSE about the relationship between 147N and 167N?
These are two different isotopes of nitrogen.
Both atoms have 7 protons.
The atoms have different atomic masses.
Both atoms have 7 neutrons.
Answer: D
These isotopes have different masses (14 and 16), but the same number of protons (7). To find the neutrons, calculate mass minus protons.

46. Which of the following is the best example of a trigonal planar molecule?
CO2
BF3
NH3
H2O
Answer: B
This molecule does not have enough valence electrons to follow the octet rule because it only needs six valence electrons. The fluorine atoms repel each other at 120 degree angles.

47. The wavelength of light released when an electron drops from n=4 to n=3 is
1282 nm
656 nm
1875 nm
97 nm
Answer: C
According to the Bohr model on page 8 of the reference tables, the wavelength is 1875 nm when the electron makes that transition from ring 4 to ring 3.

48. A + B ↔ C
What is the equilibrium constant for this reaction?
[A][B]
Answer: D
Keq = products divided by reactants

49. In what state is water at extremely low pressure and high temperature according to a phase diagram?
Liquid
Gas
Solid
Solid and Liquid
Answer: B

50. What is the formula of lithium phosphate?
Li2PO4
Li3 PO3
Li2PO2
Li3PO4
Answer: D
Lithium has a +1 charge, and phosphate has a -3 charge. You can look up phosphate on the list of polyatomic ions. When you cross charges, your subscripts will be 3 and 1, respectively.

51. What is the forward activation energy for the following reaction
What is the forward activation energy for the following reaction? (in kilojoules)
20 kJ
50 kJ
100 kJ
150 kJ
Answer: B
The activation energy is represented by (a), and is the difference between 200 kJ and 150 kJ.

52. The pressure of a mixture of nitrogen, carbon dioxide, and oxygen is 150 kPa. What is the partial pressure of oxygen if the partial pressure of nitrogen is 100 kPa and that of carbon dioxide is 24 kPa?
51 kPa
26 kPa
35 kPa
Not enough information is given
Answer: B
Dalton’s Law of Partial Pressures: Ptotal=P1+P2+P3+… Plug in the given pressures and subtract to solve.

53. When a metal oxide reacts with water, _______________ is always produced.
a base
a pink precipitate
an acid
some bubbles
Answer: A
This is a synthesis type 1b reaction.
MO + H2O  base
Remember that bases have the formula MOH.

54. Which ion is represented by this Bohr model?
Si2-
Neon
Al3+
Ca+2
Answer: C
The aluminum ion has a positive charge of 3, thus losing 3 electrons. 13 – 3 = 10
So its Bohr model would have 10 electrons.

55. Which of these types of electromagnetic radiation has the highest frequency?
X rays
Visible Light
Microwaves
Radio waves
Answer: A
It has the shortest wavelength and therefore the highest frequency. Use page 8 of the reference tables.

56. What type of reaction is:
C2H4 + O2  CO2+ H2O
combustion
decomposition
synthesis
double replacement
Answer: A
It is a reaction between a hydrocarbon and oxygen that produces CO2 and H2O. Reaction type 5 in the reference tables.

57. Which set contains a correctly named chemical formula?
Iron(III) phosphate, FePO4
Iron(II) phosphate, FePO4
Iron phosphate, FePO4
None of the above
Answer: A
Iron has to show its charge in its name because it may vary in charge number. Because the iron and phosphate have the same charge, they have a 1:1 mole ratio.

58. A gas at 89C occupies a volume of 0. 671 L
A gas at 89C occupies a volume of L. At what temperature will the volume increase to 1.12 L?
66.7C
331C
100C
None of the above
Answer: B
Put T1 in Kelvin, use Charles’ Law : V1/T1=V2/T2, to find the final temperature, then convert back to Celsius

59. Predict the products of the reaction
NaHCO3
Na + H2 + CO2
Na2O + H2O + CO2
NaO + H2O + CO2
C2H6 + Na
Answer: B
This is a decomposition type 2c, metallic hydrogen carbonate decomposes into metal oxide, water and carbon dioxide.
MHCO3 MO + H2O + CO2
Remember to cross charges to get formula for MO.

60. How many electrons are in the sodium ion? (Na+ )23 20 11 10
Answer: D
When an ion of sodium forms, it loses an electron. Originally sodium has 11 electrons so when the ion forms, the number of electrons decreases to 10 to have a filled outer shell.

61. Which of the following changes to a system will not result in an increase in pressure?
Adding more gas molecules
Increasing the volume of the container
Raising the temperature
Decreasing the volume of the container
Answer: B
Increasing the volume of the container gives the molecules more room, thus decreasing the number of collisions with the surfaces and decreasing the pressure.