BIOL 1406 EXAM 1 (CH 1-4)

For an atom to be electrically neutral, it must be true that the number of _____.

protons equals the number of electrons

The chemical formula for carbon dioxide is CO₂. How would you modify the formula to show six molecules of carbon dioxide?

6CO₂

The atomic number of an element is the number of _____.

protons in the nucleus

The chemical formula of a molecule of glucose is C₆H₁₂O₆. One glucose molecule has how many atoms of oxygen?

6

Methane is a molecule made of one carbon and four hydrogens. Identify the chemical formula for methane.

CH₄

Identify the components of an atom found in the nucleus.

neutrons and protons

Identify the example(s) of energy from the choices provided.

Electricity, light, sound, and heat

Something that has mass and occupies space is referred to as _____.

matter

An atom that has one proton, one neutron, and one electron would have an overall charge of _____.

0

Water can occur in three states: as a solid (ice), as a liquid, and as a gas (water vapor). Which state of matter has a defined volume and a defined shape?

Solid

Matter is something that _____.

has mass and occupies space

If an atom has a net negative charge, it must have _____.

more electrons than protons

Energy is often explained as the ability to _____.

do work

Oxygen has an atomic number of 8. What does this indicate?

Oxygen has 8 protons in its nucleus

What is the difference between nitrogen-14 and nitrogen-15?

Nitrogen-15 has one more neutron than nitrogen-14

Which elementary particle is found orbiting outside the nucleus of an atom?

Electrons

Atoms of the same element that have different numbers of neutrons are called _____.

isotopes

Interpret the chemical formula 6H₂O.

Six molecules of H₂O

Glucose has a chemical formula of C₆H₁₂O₆. What would be the proper way to identify two molecules of glucose?

2C₆H₁₂O₆

Carbon-12 and carbon-13 have the same number of _____.

protons and electrons

If an element has an atomic number of 7 and an atomic mass of 15, that element has _____.

seven protons and eight neutrons

The value that identifies the number of protons and neutrons in the nucleus of an atom is the _____.

atomic mass

What type of elementary particles have negative charges?

electrons

Glucose has the chemical formula C₆H₁₂O₆. Which element is not found in glucose?

Nitrogen

What type of elementary particles have positive charges?

Protons

A compound is a molecule composed of atoms of more than one type of element. Which of the following would be classified as compounds?

CO₂

H₂O

What elements are found in the compound NaCl?

Sodium Chlorine

What would be the expected number of electrons surrounding the nucleus of a neutral atom with an atomic number of 6?

6

For each of the functional groups shown, R represents the remainder of the molecule the functional group is part of.

Which functional group is called an amino group?

Differences in electronegativity lead to _____.

polarity

Which type of bond is formed when one atom loses one or more electrons and another atom gains those electrons?

Ionic

Which type of bond involves the interaction of atoms that carry full negative and full positive charges?

Ionic

Which element listed has the lowest abundance in living organisms?

Magnesium

The formation of which type of bond requires the presence of a catalyst called an enzyme in order to occur at a biologically relevant rate?

Covalent

The electronegativities of the most common elements in biology are as follows:

Hydrogen	2.1
Carbon	2.5
Oxygen	3.5
Nitrogen	3.0

Which element above has the greatest attraction for electrons?

Oxygen

Which type of bond is created when atoms are held together by the sharing of electrons?

Covalent

Identify the most appropriate term for the molecule below.

amphipathic

Hydrogen is much less electronegative than nitrogen. In an N-H bond, the hydrogen would be _____.

partially positive

Which molecule possesses an ionic bond?

The portion of the fatty acid below bound by the red rectangle is _____.

hydrophobic

Which element listed has the lowest abundance in living organisms?

Calcium

The shape below represents an organic (carbon-based) molecule with a functional group consisting of carbon, hydrogen, and oxygen:

 The functional group is called a _____ group.

carboxyl

Recall that the primary elements in biology are carbon (C), hydrogen (H), nitrogen (N), oxygen (O), phosphorous (P), and sulfur (S).  C, H, P, and S have biologically similar electronegativities, while O and N are significantly higher than the others in electronegativity.

Which bond is least likely to demonstrate polarity (partial charge)?

C-H

The shape below represents an organic (carbon-based) molecule with a functional group consisting of oxygen and phosphorous:

 

The functional group is called a(n) _____ group.

phosphate

Bonds formed from the equal sharing of electrons are called _____.

nonpolar covalent

Bonds formed from the unequal sharing of electrons are called _____.

polar covalent

For each of the functional groups shown, R represents the remainder of the molecule the functional group is part of.

Which functional group is called a methyl group?

In what way do hydrogen bonds differ from covalent bonds?

Hydrogen bonds are the result of the weak attraction of the hydrogen in a polar bond with a more electronegative atom in another polar bond.

Which red arrow identifies a hydrogen bond?

For each of the functional groups shown, R represents the remainder of the molecule the functional group is part of.

Which functional group is called a hydroxyl group?

Covalent bonds are formed when _____.

a pair of electrons is shared between two atoms

When the pair of electrons in a covalent bond spend more time around one atom than the other, this is due to a difference in _____ between the two atoms.

electronegativity

Which of the covalent bonds shown is a polar covalent bond?

O-H

The shape below represents an organic (carbon-based) molecule with a functional group consisting of carbon, hydrogen, and oxygen:

 

The functional group is called a _____ group.

carboxyl

Which element listed has the highest abundance in living organisms?

Carbon

The human body is composed primarily of _____.

water

Water exists in three states, solid, liquid, and gas. Identify the state(s) where hydrogen bonding occurs among water molecules.

liquid and solid

The evaporation of sweat cools skin because of the _____ of water.

high heat of vaporization

Identify the property that describes the attraction of water molecules to molecules other than water.

Adhesion

The figure below represents two water molecules interacting with each other:

What type of bond is identified by the red arrow?

Hydrogen bond

When a narrow glass tube is placed in a beaker of pure water, what will happen?

The water will rise in the tube above the level of the water in the beaker

When NaCl (table salt) is dissolved in water, _____ is the solvent and _____ is the solute.

water, NaCl

The figure below is linoleic acid, a common fatty acid in sunflower oil:

 

If drops of sunflower oil are placed into a beaker of water, what is most likely to happen? (Hint: the electronegativity value of carbon is 2.5 and the electronegativity value of hydrogen is a biologically-similar 2.1)

The droplets of oil will accumulate in the center of the beaker of water and form a layer dividing the water in half.

The curved surface of water in a clean glass tube is due to _____.

the high surface tension of the water

Both beakers below contain pure water. The beaker on the left contains 500 ml of water, and the beaker on the right contains 200 ml of water:

 

            

The specific heat of the water in the beaker on the left is _____ the specific heat of the water in the beaker on the right.

the same as

Identify the property that describes the attraction of water molecules to other water molecules.

Cohesion

Which molecule would be insoluble in water?

The figure below represents two water molecules interacting with each other:

What type of bond is identified by the red arrow?

Polar covalent bond

The substance in a solution which is dissolved into the other substance is called the _____.

solute

When oil and water are mixed, why do they immediately begin to separate?

Oil is mostly hydrophobic, and will not dissolve into the water by forming hydrogen bonds with water molecules.

Why does ice float on water?

Ice floats because water molecules in ice are further apart than water molecules in liquid water, and thus less dense.

The substance in a solution which dissolves the other substance is called the _____.

solvent

In a molecule of water, the oxygen is _____ and the hydrogens are _____.

partially negative, partially positive

The evaporation of sweat cools skin because of the _____ of water.

high heat of vaporization

What property of water allows it to moderate the temperature of the Earth?

High specific heat

An insect's ability to walk on water is due to what property of water?

High surface tension

Cohesion in mercury is higher than cohesion in water. If mercury is placed in one container and an equal volume of water is placed in a second container, what is the relationship between the distance traveled for each in similar sized capillary tubes place in the respective containers?

Water will travel a greater distance than mercury.

Which factor or factors contribute to the movement of water from the roots of a tree to the leaves?

Adhesion, capillary action, and cohesion

When a drop of water is placed carefully on a microscope slide, it forms a bead-like drop instead of flattening to a thin layer. This is due to the _____ of the water molecules.

cohesion

Which statement about water is correct?

Water has cohesive properties

A solution with a pH of 2 has a proton concentration _____ than a solution with a pH of 4.

100 times higher

In an aqueous solution, the concentration of hydrogen ions [H⁺] times the concentration of hydroxide ions [OH^–] equals _____.

10^–14 M

Which substance is the most acidic?

Tomatoes

Every unit on a pH scale represents what change in hydrogen ion concentration?

10-fold

A substance that donates hydrogen ions in solution is referred to as a(n) _____.

acid

A substance with a pH value of 8.5 is _____.

basic

Buffers are commonly _____.

weak acids

For simplicity, hydrogen ions are represented as H⁺. What is a more chemically accurate representation of hydrogen ions in pure water?

H₃O⁺

A substance with a pH value of 4.5 is _____.

acidic

What substance has a hydrogen ion concentration of 10^–2 M?

Lemon juice

What is the pH of a solution with a proton (H⁺) concentration of 0.1 M?

1

A base can reduce the hydrogen ion concentration of a solution by _____.

directly accepting hydrogen ions

releasing hydroxide ions which combine with hydrogen ions to form water

What is the reason that NaCl is not considered an acid when it dissolves in water?

No hydrogen ions are released into the solution.

A solution with a pH of 8 has a proton concentration _____ than a solution with a pH of 5.

1,000 times lower

A solution with a high concentration of hydrogen ions (H⁺) _____.

is an acid and has a low pH

Identify the correct statement(s) about a hydronium ion.

It is one of the products of the dissociation of water in solution

It has a formula of H₃O⁺

What is the H₃O⁺ concentration of pure water?

10^–7 M

What is the hydrogen ion concentration of household ammonia?

10^-12 M

Which substance has an equal concentration of hydrogen ions and hydroxide ions?

Pure water

Baking soda has a hydrogen ion concentration _____ than lye.

10⁵ times higher