Reaction Chemistry (10%)

Question 1

Which of the following elements does not have a noble gas configuration?

(A) Na (sodium)
(B) He (helium)
(C) Ar (argon)
(D) Ne (neon)
(E) they are all noble gases

Answer 1

(A) Na (Sodium)

Question 2

The atomic masses of carbon and oxygen are 12 and 16, respectively. What is the approximate percent by mass of oxygen in carbon dioxide, CO2?

(A) 25% 
(B) 50% 
(C) 66% 
(D) 75%
(E) 85%

Answer 2

(D) 75%

12 (C) + 16 (O) + 16 (O) = 44

32 (O2) / 44 = 0.73 (73%) - Closest answer.

Question 3

Within molecules of a compound, atoms are held together by chemical bonds that are primarily

(A) thermal 
(B) frictional 
(C) gravitational 
(D) electrostatic 
(E) magnetic

Answer 3

(D) electrostatic

Question 4

CaO+CO2→CaCO3

What mass of CaO is needed to absorb 22 grams of CO2 according to the balanced chemical equation above? (Molar masses: CaO=56g/mol, CO2=44g/mol
)

(A) 112 g 
(B) 100 g 
(C) 56 g 
(D) 28 g 
(E) 22 g

Answer 4

(D) 28 g

How to solve:

56 44
—- —-
x 22

Question 5

2NO2(g)→←N2O4(g)

The equation above represents a system that has reached a state of chemical equilibrium. Which of the following is a true statement about the system?

(A) All chemical reaction rates have dropped to zero.
(B) The system will eventually contain only N2O4 molecules.
(C) The concentration of NO2(g) must be twice that of N2O4(g).
(D) The concentration of NO2(g) must be less than that of N2O4(g).
(E) N2O4 molecules are being consumed as fast as they are produced.

Answer 5

(E) N2O4 molecules are being consumed as fast as they are produced.

Question 6

The following reaction is an example of which type of reaction?

2NaN3(s)→3N2(g)+2Na(s)

(A) combination 
(B) replacement 
(C) decomposition
(D) double displacement 
(E) none of the above

Answer 6

(C) decomposition

Question 7

In old-fashioned flashbulbs, light was produced by the reaction of magnesium metal, Mg, sealed in the bulb with oxygen gas, O2. After the flash, the mass of the sealed bulb was

(A) definitely greater than it was before use
(B) definitely smaller than it was before use
(C) essentially the same as it was before use
(D) greater or smaller depending on the amount of O2
consumed
(E) greater or smaller depending on the amount of light produced

Answer 7

(C) essentially the same as it was before use

Question 8

Which term best describes the bonds between Hydrogen and Oxygen in a molecule of water?

(A) salt 
(B) strong 
(C) ionic 
(D) covalent 
(E) non-polar

Answer 8

(D) covalent

Reason: The formation of water molecules provides an example of covalent bonding. The hydrogen and oxygen atoms that combine to form water molecules are bound together by covalent bonds. The electron from the hydrogen splits its time between the incomplete outer shell of the hydrogen atoms and the incomplete outer shell of the oxygen atoms. To completely fill the outer shell of oxygen, which has six electrons in its outer shell but which would be more stable with eight, two electrons (one from each hydrogen atom) are needed: hence the well-known formula H2O. The electrons are shared between the two elements to fill the outer shell of each, making both elements more stable.

Question 9

Which of the following are the four elements that are the basis of organic chemistry?

(A) H, O, P, S 
(B) C, H, O, N
(C) B, C, N, O 
(D) Na, K, Mg, Ca 
(E) C, H O, F

Answer 9

(B) C, H, O, N

Question 10

A _____ is two or more atoms held together by shared electrons – like H2.

(A) Molecule
(B) Compound
(C) Covalent
(D) Ionic

Answer 10

(A) Molecule

Question 11

A _____ is two or more different elemental atoms bond together through the sharing of electrons – like water!

(A) Molecule
(B) Compound
(C) Covalent
(D) Ionic

Answer 11

(B) Compound

Question 12

Atoms will exchange or share electrons in order to fill the valence shell. This is called

(A) Covalent
(B) Ionic
(C) Chemical bonding
(D) Valence shell electrons

Answer 12

(C) Chemical bonding

Question 13

There are two common modes of bonding: _____, where a pair of electrons is SHARED. _____ where electrons are EXCHANGED.

(A) Ionic, Covalent
(B) Covalent, Ionic
(C) Molecular, Compound
(D) Compound, Molecular

Answer 13

(B) Covalent, Ionic

Question 14

H20 (Water) has _____ valence shell electrons. The magic number!

(A) 2
(B) 4
(C) 6
(D) 8

Answer 14

(D) 8

Question 15

When a molecule is presented in a stick configuration (H-0-2), the “sticks” represent

(A) Electrons being shared
(B) Electrons being exchanged
(C) Protons being shared
(D) Protons being exchanged

Answer 15

(A) Electrons being shared

Question 16

In _____, one atom loses an electron and another takes it.

(A) Covalent bonding
(B) Ionic bonding
(C) Chemical bonding
(D) None of the above

Answer 16

(B) Ionic bonding

Question 17

In ionic bonding, the atom that loses an electron has a (+) charge, and is called a

(A) Anion
(B) Cation
(C) Ion

Answer 17

(B) Cation

Question 18

In ionic bonding, the atom that gaines an electron has a (-) charge, and is called a

(A) Anion
(B) Cation
(C) Ion

Answer 18

(A) Anion

Question 19

Chemical reactions occur when molecules or atoms interact with each other. Reactions are symbolized with an arrow showing reaction progress from _____ to _____.

(A) Products to reactants
(B) Reactants to products

Answer 19

(B) Reactants to products

Question 20

In this chemical reaction type, the reaction often starts with a single reactant that degrades into multiple products:

AB → A + B

(A) Decomposition
(B) Combination
(C) Replacement
(D) Double displacement

Answer 20

(A) Decomposition

Question 21

In this chemical reaction type, the reaction often starts with multiple reactants that react to form a single product:

A + B → AB

(A) Decomposition
(B) Combination
(C) Replacement
(D) Double displacement

Answer 21

(B) Combination

Question 22

In this chemical reaction type, one compound breaks apart and forms a new compound with a different reactant:

AB + C → AC + B

(A) Decomposition
(B) Combination
(C) Replacement
(D) Double displacement

Answer 22

(C) Replacement

Question 23

In this chemical reaction type, two compounds break apart and exchange components to form new compounds:

AB + CD → AC + BD

(A) Decomposition
(B) Combination
(C) Replacement
(D) Double displacement

Answer 23

(D) Double displacement

Question 24

A chemical reaction can also be categorized as an oxidation or a reduction. (Remember LEO GER). Element that loses electrons = _____.

(A) Oxidation
(B) Reduction

Answer 24

(A) Oxidation

Question 25

A chemical reaction can also be categorized as an oxidation or a reduction. (Remember LEO GER). Element that gains electrons = _____.

(A) Oxidation
(B) Reduction

Answer 25

(B) Reduction

Question 26

Chemical reactions are either

(A) Exothermic
(B) Thermic
(C) Endothermic
(D) A and C
(E) B and C

Answer 26

(D) A and C (Exothermic and Endothermic)

Question 27

This type of chemical reaction releases energy.

(A) Exothermic
(B) Endothermic

Answer 27

(A) Exothermic

Question 28

This type of chemical reaction requires an input of energy to proceed.

(A) Exothermic
(B) Endothermic

Answer 28

(B) Endothermic

Question 29

All reactions must follow the laws of

(A) Exothermic
(B) Endothermic
(C) Thermodynamics

Answer 29

(C) Thermodynamics

Question 30

In the laws of thermodynamics, matter and energy can be created and destroyed.

(A) True
(B) False

Answer 30

(B) False

1. The law of conservation of energy and matter – matter and energy can be neither created or destroyed.

Energy and matter must always be balanced.

Question 31

In the laws of thermodynamics, all reactions spread energy, which will tend to diminish its availability.

(A) True
(B) False

Answer 31

(A) True

2. The law of increasing disorder (entropy) – all reactions spread energy, which will tend to diminish its availability.

Reactions progress to degrade potential energy.

Question 32

_____ has a number of properties that make it a unique substance:

• It is polar
• It expands when frozen (solid phase is less dense than liquid phase)
• High specific heat
• High surface tension

(A) Gas
(B) Water
(C) Metal
(D) Vapor

Answer 32

(B) Water

Question 33

Water’s hydrogen bonding interactions lead to

(A) Low surface tension
(B) High surface tension
(C) Low pressure
(D) High pressure

Answer 33

(B) High surface tension

Question 34

In organic chemistry, _____ is really important because the skeleton of the organic compound is often built up almost entirely of this.

(A) Carbon
(B) Hydrogen
(C) Oxygen
(D) Nitrogen

Answer 34

(A) Carbon