Chapter 2a and 2b Exam 1

Question 1

What are the four most common elements in living organisms?
A) C, H, O, Fe.
B) C, H, O, Na.
C) C, H, O, N.
D) C, N, O, Na.

Answer 1

C) C, H, O, N.
Note: C is carbon, H is hydrogen, O is oxygen, and N is nitrogen. The next common elements are phosphorus(P), sulphur (S), sodium (Na), potassium (K), and calcium (Ca), and iron (Fe)

Question 2

Which of the following is a trace element in the human body?
A) nitrogen
B) zinc
C) oxygen
D) hydrogen

Answer 2

B) Zinc.
Other trace elements needed in the body include: Cu,Zn, Mo, I, F, Co, Se, etc. The following elements are NOT considered trace elements: C,H,O, N, S (sulphur), P (phosphorus), Na, K, Ca, and Fe. All other elements needed by the body that are not these are considered “trace elements”. The choices in the actual exam WILL change.. Note, you are also expected to recognize the symbols of these common elements, and you may NOT get the word in the actual exam.

Question 3

Which of the following statements regarding matter is false?
A) All life is composed of matter.
B) All matter has mass.
C) All matter is composed of elements.
D) All matter exists in the form of compounds.

Answer 3

D) All matter exists in the form of compounds.
Note: Compounds are made up of one or more elements.

Question 4

Which statement best describes a compound?
A) A compound is a pure element.
B) A compound contains two or more different elements in a fixed ratio.
C) A compound is exemplified by sodium.
D) A compound is a solution.

Answer 4

B) A compound contains two or more different elements in a fixed ratio.

Question 5

In the equation 2 H2 + O2 → 2 H2O, which is true?
A) H2, O2, and H2O are all compounds.
B) H2, O2, and H2O are all elements.
C) only H2O is a compound.
D) only H2 and O2 are compounds.

Answer 5

C) only H2O is a compound.
Note: The left side of a chemical equation are the reactants and the right side are the products. Compounds are made up of more than 1 element.

Question 6

Which particles are found in the nucleus of an atom?
A) protons and neutrons
B) protons and electrons
C) only protons
D) only electrons

Answer 6

A) Protons and neutrons.
Note: electrons orbits (roams very quickly !) the positively charged nucleus. Please also remember each proton has 1 positive charge, each electron has 1 negative charge, and neutrons have no charge.

Question 7

What is the atomic mass of an atom with 6 protons, 6 neutrons, and 6 electrons?
A) 6
B) 8
C) 12
D) 18

Answer 7

C) 12.
Note: Atomic mass is the number of protons plus the number of neutrons. The actual question will change in the exam ! Each proton and each neutron in an atom is assigned 1 unit of mass. Electrons are much much lighter than protons and neutrons and are not included in the calculations of atomic mass.

Question 8

An uncharged atom of boron has an atomic number of 5 and an atomic mass of 11. How many electrons does an uncharged atom of boron with atomic number 5 have?
A) 11
B) 15
C) 5
D) 2

Answer 8

C) 5.
Note: Atomic number is the number of protons only. Mass number (atomic mass) is the number of protons + number of neutrons. In an element of the elemental state, the number of electrons equals the number of protons. The actual number will change in the exam.

Question 9

What is another term used for atomic mass?
A) darwin
B) mendel
C) dalton
D) calvin

Answer 9

C) Dalton.

Question 10

What is the mass number of sodium with 11 electrons, 11 protons, and 12 neutrons?
A) 11
B) 22
C) 23
D) 34

Answer 10

C) 23.
Note: Mass number is the number of protons + number of neutrons. Number of electrons is irrelevant. For any element in its native elemental state, the number of electrons should equal the number of protons.

Question 11

What best describes the atomic number of an atom?
A) the number of protons in the atom
B) the number of electrons in the atom
C) the number of neutrons in the atom
D) the number of protons, electrons, and neutrons in the atom

Answer 11

A) The number of protons in the atom.

Question 12

An isotope of nitrogen could have more what?
A) be positively charged.
B) be negatively charged.
C) have more protons than the usual nitrogen atom.
D) have more neutrons than the usual nitrogen atom.

Answer 12

D) have more neutrons than the usual nitrogen atom.
Note: you must have the same number of protons to be the same element. Isotopes means the same element with the same number of protons but different numbers of neutrons

Question 13

When full, the innermost electron shell of argon contains ________ electrons, and the outermost shell contains ________ electrons.
A) 2 . . . 2
B) 2 . . . 8
C) 4 . . . 8
D) 8 . . . 8

Answer 13

B) 2 . . . 8.

Question 14

What happens if the electrons in the outer shell of an atom are altered?
A) The atom becomes radioactive.
B) The atom will disintegrate.
C) The properties of the atom will change.
D) The atom’s characteristics change and it becomes a different element.

Answer 14

C) The properties of the atom will change.
Note: if an atom loses an electron, the atom becomes positively charged and is called a cation. If an atom gains an electron, it becomes negatively charged and is called an anion.

Question 15

What forms when two atoms share electrons?
A) ion
B) covalent bond
C) ionic bond
D) hydrogen bond

Answer 15

B) Covalent bond.

Question 16

How many covalent bonds can a hydrogen atom form?
A) one covalent bond
B) two covalent bonds
C) four covalent bonds
D) no covalent bonds

Answer 16

A) One covalent bond.
Note: hydrogen can either form a single covalent bond or loses the electron to form H+ ion and form ionic bonds with other anions

Question 17

Table salt is formed when?
A) chlorine gives an electron to sodium.
B) a hydrogen bond forms between sodium and chlorine.
C) sodium and chlorine share electrons to form a bond.
D sodium ions forms ionic bonds with chloride ions

Answer 17

D) sodium ions form ionic bonds with chloride ions.

Question 18

Medicines are often administered in pill form. In many cases, the active ingredient of the pill (the drug) is joined to another substance by ________. This forms a(n) ________, which is stable in the dry environment of a pill bottle but dissociates under the wet conditions of the digestive system to release the drug to the body.
A) ionic bonds . . . salt
B) hydrogen bonds . . . base
C) ionic bonds . . . acid
D) covalent bonds . . . salt

Answer 18

A) Ionic bonds . . . salt.
Note: any ionic compounds formed by a cation and an anion can be called “salt”. It doesn’t not necessarily mean sodium chloride (the common table salt)

Question 19

What is the fundamental difference between covalent and ionic bonding?
A) In a covalent bond, the partners share a pair of electrons; in an ionic bond, oppositely charged ions attract each other
B) In covalent bonding, both partners end up with filled outer electron shells; in ionic bonding, one partner does and the other does not.
C) Covalent bonding involves only the outermost electron shell; ionic bonding also involves the next electron shell inside the outermost shell.
D) Covalent bonds form between atoms of the same element; ionic bonds form between atoms of different elements.

Answer 19

A) In a covalent bond, the partners share a pair of electrons; in an ionic bond, oppositely charged ions attract each other.

Question 20

Which statement regarding the oxygen atom of a water molecule is true?
A) Oxygen is more positively charged than the hydrogen atoms.
B) Oxygen attracts electrons less strongly than the hydrogen atoms.
C) Oxygen is more electronegative than the hydrogen atoms.
D) Oxygen is attracted to the negatively charged atoms of other molecules.

Answer 20

C) Oxygen is more electronegative than the hydrogen atoms.

Question 21

In a water molecule, how are hydrogen and oxygen held together?
A) double covalent
B) nonpolar covalent
C) hydrogen
D) polar covalent

Answer 21

D) Polar covalent.

Question 22

What type of bonds hold a water molecule together?
A) a single covalent bond.
B) a double covalent bond.
C) two polar single covalent bonds.
D) hydrogen bonds.

Answer 22

C) two polar single covalent bonds.
Note: hydrogen and oxygen share electrons unequally, they form polar covalent bonds as a result

Question 23

What type of bonds are between hydrogen atoms of a water molecule and the oxygen atom?
A) hydrogen . . . polar covalent
B) polar covalent . . . hydrogen
C) ionic . . . covalent
D) polar covalent . . . ionic

Answer 23

B) Polar covalent . . . hydrogen.
Note: covalent bonds are typically represented by solid lines. Hydrogen bonds are typically represented by dotted lines. Covalent bonds are >100 times stronger than hydrogen bonds. When you boil water to evaporation, you’ll only be separating the hydrogen bonds between adjacent water molecules. The covalent bonds within the water molecules stay intact!

Question 24

________ are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
A) Ionic bonds
B) Covalent bonds
C) Polar covalent bonds
D) Hydrogen bonds

Answer 24

D) Hydrogen bonds.

Question 25

Water molecules stick to other water molecules because A) water molecules are neutral, and neutral molecules are attracted to each other. B) hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules. C) covalent bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules. D) the oxygen atoms of adjacent water molecules are attracted to one another.

Answer 25

B) hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.

Question 26

Which statement regarding chemical reactions is false? A) Chemical reactions involve the making and breaking of chemical bonds. B) Some chemical reactions create electrons; others destroy them. C) The reactants contain the same number of atoms as the products. D) Although the atoms of a reaction's reactants and products are identical to each other, their molecular formulae differ.

Answer 26

B) Some chemical reactions create electrons; others destroy them. Note: That’s never true. If electrons/protons/neutrons are transferred or created, those are called nuclear reactions, NOT chemical reactions.

Question 27

In the equation 2 H2 + O2 → 2 H2O, the H2 molecules are ________ and the H2O molecules are ________. A) reactants . . . products B) products . . . reactants C) created . . . destroyed D) used . . . stored

Answer 27

A) Reactants . . . products.

Question 28

What is the tendency of water molecules to stick together called? A) adhesion. B) polarity. C) cohesion. D) transpiration.

Answer 28

C) Cohesion.

Question 29

What accounts for water's surface tension and heat storage capacity? A) orbitals. B) hydrogen bonds. C) mass. D) size.

Answer 29

B) Hydrogen bonds.

Question 30

What happens as ice melts? A) hydrogen bonds are broken. B) water molecules become less tightly packed. C) the water becomes less dense. D) heat is released.

Answer 30

A) hydrogen bonds are broken.

Question 31

Which statement about water is false? A) Ice is more dense than liquid water. B) Water naturally exists in all three physical states on Earth. C) Floating ice on a pond insulates the liquid water below, slowing its rate of freezing. D) If ice sank, the oceans would eventually freeze solid.

Answer 31

A) Ice is more dense than liquid water. Note: ice is less dense than water because the distance between adjacent water molecules is actually greater than that in liquid water. Therefore, ice floats on water.

Question 32

What have you prepared by dissolving instant coffee and sugar in hot water? A) You've just prepared an aqueous solution. B) The water is the solute portion of the drink. C) The instant coffee and sugar are solvents. D) The instant coffee and sugar dissolve because they have no charged regions to repel the partial positive and partial negative regions of the water molecules.

Answer 32

A) You've just prepared an aqueous solution. Note: water is the solvent, the coffee is the solutes, and dissolving a solute in a solvent makes a solution

Question 33

What is dependent on the ability of water molecules to form hydrogen bonds with other molecules? A) the evaporative cooling of skin surfaces B) the milder temperatures of coastal regions compared to inland areas C) the ability of certain insects to walk on the surface of water D) the universality of water as a solvent

Answer 33

D) The universality of water as a solvent. Note: The first 3 are inherent properties of water

Question 34

What is a solution with a pH of 7? A) strongly acidic. B) weakly acidic. C) neutral. D) weakly basic.

Answer 34

C) Neutral. Note: You are expected to know pH>7 is alkaline and pH< 7 is acidic. The value of this question WILL change.

Question 35

Compared to a solution of pH 3, a solution of pH 1 is? A) 100 times more acidic. B) 10 times more acidic. C) 10 times more basic. D) 100 times more basic.

Answer 35

A) 100 times more acidic. Note: You’ll need to calculate the difference in acidity level with any given pH numbers. The number appearing on this question WILL change.. You should know that pH is a negative log scale. Every unit decrease means 10 times more acidic than the previous one! For instance, pH2 is 10x10x10x10 =104 or 10000 times more acidic than pH 6. The easiest way to compute this is simply 10(6-2) = 104 = 10,000 times. You should be familiar with scientific notation format. Answers are likely given in scientific notations instead of a number of zeros written out.

Question 36

Which statement about pH is true? A) The pH scale is a measure of oxygen ion concentration. B) A single unit change on the pH scale is equivalent to a 1% change in hydrogen ion concentration. C) An increase in hydrogen ion concentration means a decrease in pH scale units. D) Basic pH levels are less than 7.

Answer 36

C) An increase in hydrogen ion concentration means a decrease in pH scale units. Note: A single unit change on the pH scale is equivalent to 10 times change in H+ concentration !

Question 37

What is true about household ammonia and bleach? A) Both of these substances are strong acids. B) The ammonia has 10 times as many OH- ions as the bleach. C) The ammonia has 10 times as many H+ ions as the bleach. D) A solution that could buffer the bleach and ammonia would remove excess OH- ions.

Answer 37

C) The ammonia has 10 times as many H+ ions as the bleach. Note: Remember pH is a logarithmic scale. Every time you go up and down a pH unit, you are adding or removing 1 zero. pH12 is has 10x more H+ (or more acidic than) pH13, or pH13 has 10x more OH- (more alkaline) than pH12. In this case, ammonia has 10 times less H+ compared to household bleach.

Question 38

What is a buffer? A) is an acid that is used to offset overly basic conditions in the body. B) is a base that is used to offset overly acidic conditions in the body. C) donates H+ ions when conditions become too basic and accepts H+ ions when conditions become too acidic. D) donates OH- ions when conditions become too basic and accepts OH- ions when conditions become too acidic.

Answer 38

C) donates H+ ions when conditions become too basic and accepts H+ ions when conditions become too acidic.

Question 39

What do the hydrogen bonds shown in the figure represent? A) between two hydrogen atoms. B) between an oxygen and a hydrogen atom of the same water molecule. C) between an oxygen and a hydrogen atom of different water molecules. D) between two atoms with the same charge.

Answer 39

C) between an oxygen and a hydrogen atom of different water molecules. Remember: with the H2O molecule, hydrogen and oxygen are held together by polar covalent bonds (real electron sharing, albeit unequally) , and adjacent water molecules are attracted to each other by weak hydrogen bonds. A covalent bond is at least 100x stronger than a hydrogen bond. You've been experiencing acid indigestion lately, and you'd like a quick fix for the problem. You do a little research on the Internet and discover that your problem is caused by excess stomach acid. In the pharmacy aisles, however, you're having a little trouble deciding what to purchase to address the problem. At the pharmacy counter, the clerk recommends that you purchase Pepcid-AC® or Alka-Seltzer® tablets.

Question 40

What would you expect the pH of the recommended tablets to be? A) higher than 7. B) lower than 7. C) exactly 7. D) pH neutral.

Answer 40

A) higher than 7. Note: most antacid tablets (e.g. calcium carbonate or milk of magnesia) when dissolved in water will give you are pH of about 10.

Question 41

What would you find in stomach fluids after taking two tablets? A) more hydrogen ions. B) fewer hydrogen ions. C) the same number of hydrogen ions. D) that the pH in your stomach has decreased.

Answer 41

B) fewer hydrogen ions. Remember lower pH means more acidic or more H+ ions present. After taking 2 antacid tablets, you’ll expect some of the acid has been neutralized and the pH has increased or less H+ ions.

Question 42

Which are the most electronegative elements?

Answer 42

#1: Fluorine, #2: Oxygen, #3: Chlorine. you’ll need to be able to rank these 3 in the exam.