Chemistry Chapter 2 Flashcards

Questions and Answers

Adhesion is best described as _____.

the clinging of one substance to another substance

You can fill a glass of water to just slightly above the rim without it spilling over the glass. What property of water best explains this phenomenon?

None of the listed responses is correct

Surface tension (correct)

Adhesion

Evaporative cooling

Its polarity

Which action would involve the greatest transfer of heat?

Evaporating 1 g of water at 25°C

Condensing 5 g of steam to liquid water (correct)

Changing the temperature of 1 g of water from 10°C to 90°C

Raising the temperature of 10 g of ethyl alcohol by 25°C

Cooling 10 g of water from 80°C to 40°C

Imagine that organisms consisted of 70-95% alcohol instead of 70-95% water. Alcohol's specific heat is about half that of water. How would living things be different?

Systems for temperature regulation would have to be much more efficient. Signup and view all the answers

The amount of heat required to change the temperature of 1 g of any substance by one °C is defined as _____.

The specific heat of that substance Signup and view all the answers

The amount of heat required to convert 1 g of any substance from the liquid to the gaseous state is defined as _____.

The heat of vaporization of that substance Signup and view all the answers

The reason that coastal climates are more moderate than inland climates is due primarily to water's high _____.

Specific heat Signup and view all the answers

Sweating has a cooling effect because of water's high _____.

Heat of vaporization Signup and view all the answers

Because molecules of water are farther apart in ice than in liquid water, _____.

Ice floats Signup and view all the answers

Water is a very versatile solvent because water molecules are _____.

Polar Signup and view all the answers

How does the polarity of water contribute to its ability to dissolve so many substances?

Because it is polar, water's oppositely charged ends are attracted to positively and negatively charged ions and molecules. Water molecules form a hydration shell around oppositely charged particles. Signup and view all the answers

Nonpolar molecules that cluster away from water molecules are called _____ molecules.

Hydrophobic Signup and view all the answers

A molecule that has all nonpolar covalent bonds would be _____.

Hydrophobic Signup and view all the answers

Hydrophobic molecules are _____ water.

Repelled by Signup and view all the answers

Why are cell membranes composed primarily of hydrophobic molecules?

In order to perform their function of separating the aqueous solutions outside of cells from the aqueous solutions inside of cells, cell membranes cannot be soluble in water. Signup and view all the answers

Hydrophilic substances, but not hydrophobic substances, _____.

Have charges and partial charges to which water molecules can adhere Signup and view all the answers

Some substances, such as oil and gasoline, will not dissolve in water because _____.

Their molecules have no charges or partial charges to which water molecules can adhere Signup and view all the answers

A mole of ethyl alcohol weighs 46 g. How many grams of ethyl alcohol are needed to produce 1 L of a 2-millimolar (2 mM) solution?

0.092 g Signup and view all the answers

An acid is _____.

A compound that donates hydrogen ions to a solution Signup and view all the answers

Adding acid tends to _____ of a solution.

Increase the hydrogen ion concentration and lower the pH Signup and view all the answers

Which of the following dissociations is that of an acid?

HF → H+ + F- Signup and view all the answers

A glass of grapefruit juice, at pH 3, contains _____ H+ as a glass of tomato juice, at pH 4.

Ten times as much Signup and view all the answers

A solution at pH 6 contains _____ than the same amount of solution at pH 8.

100 times more H+ Signup and view all the answers

Adding a base tends to _____ of a solution.

Lower the hydrogen ion concentration and increase the pH Signup and view all the answers

When the pH of a solution shifts from 7 to 3, how has the hydrogen ion concentration changed?

It has increased by 10,000 times. Signup and view all the answers

A substance that minimizes changes in the concentration of H+ and OH- in a solution is a _____.

Buffer Signup and view all the answers

Sucrose has a molecular mass of 342 daltons. To make a 2-molar (2 M) solution of sucrose, _____

Stir 342 g of sucrose in water to dissolve the sugar, and then add enough water to bring the total volume of the solution up to 0.5 L Signup and view all the answers

Why is the increasing amount of carbon dioxide being taken up by the oceans a cause for concern?

More carbon dioxide causes an increase in carbonic acid (H2CO3), which leads to a decrease in the concentration of carbonate ion (CO32-). Signup and view all the answers

The reactivity of an atom arises from __________.

the existence of unpaired electrons in the valence shell Signup and view all the answers

Which of the following statements correctly describes any chemical reaction that has reached equilibrium?

The rates of the forward and reverse reactions are equal. Signup and view all the answers

Many mammals control their body temperature by sweating. Which property of water is most directly responsible for the ability of sweat to lower body temperature?

The absorption of heat by the breaking of hydrogen bonds Signup and view all the answers

We can be sure that a mole of table sugar and a mole of vitamin C are equal in their __________.

number of molecules Signup and view all the answers

Measurements show that the pH of a particular lake is 4.0. What is the hydrogen ion concentration of the lake?

10^-4 M Signup and view all the answers

The atomic number of sulfur is 16. What is the molecular formula of the compound formed when sulfur combines with hydrogen by covalent bonding?

H2S Signup and view all the answers

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products? C6H12O6->C2H6O+ CO2

2; 2 Signup and view all the answers

A slice of pizza has 500 kcal. If we could burn the pizza and use all the heat to warm a 50-L container of cold water, what would be the approximate increase in the temperature of the water?

10 degrees C Signup and view all the answers

Oxygen is not a greenhouse gas; therefore, gases containing oxygen, such as ozone, nitrous oxide, and carbon dioxide, are not greenhouse gases either.

False Signup and view all the answers

There are _____ naturally occurring elements.

92 Signup and view all the answers

Which of the following is a trace element?

Copper Signup and view all the answers

What are the four most abundant elements found in living systems?

hydrogen, oxygen, nitrogen, and carbon Signup and view all the answers

Which of the following has negligible mass?

Electron Signup and view all the answers

Which of the following subatomic particles has appreciable mass and lacks a charge?

Neutron Signup and view all the answers

The number of protons in an uncharged atom equals the number of electrons.

True Signup and view all the answers

How many neutrons does an atom with an atomic number of 4 and a net electronic charge of +1 have?

The answer cannot be determined from the information provided. Signup and view all the answers

An uncharged atom of nitrogen (atomic number = 7) has _____ protons.

7 Signup and view all the answers

Isotopes of an element will always differ in _____?

Atomic mass Signup and view all the answers

A particular carbon isotope has an atomic number of 6 and an atomic mass of 14. What are the respective numbers of neutrons, protons, and electrons?

8, 6, and 6 Signup and view all the answers

Phosphorus-32 (radioactive) has _____ than phosphorus-35 (normal).

Three fewer neutrons Signup and view all the answers

The most common form of calcium has 20 protons, 20 neutrons, and 20 electrons. Which of the following elements would be an isotope of calcium?

An atom with 20 protons, 21 neutrons, and 20 electrons Signup and view all the answers

Radioactive isotopes are useful in scientific research because _____.

They can be used as tracers to follow particular atoms and molecules through metabolic pathways. Signup and view all the answers

Potassium (atomic number 19, mass number 40) and sodium (atomic number 11, mass number 23) have similar chemical properties because uncharged atoms of potassium and sodium ______.

Have different mass numbers and each has one electron in its outermost electron shell. Signup and view all the answers

The chemical characteristics or reactivity of an element depend mostly on the _____?

Number of electrons in its outermost shell. Signup and view all the answers

Some groups of elements react chemically in similar ways. For example, the chemistry of sodium and the chemistry of lithium are similar. These similarities in chemistry result from different elements having similar _____.

Numbers of outer-shell electrons. Signup and view all the answers

How many electrons would be present in the valence shell of a sulfur atom (atomic number 16, mass number 32)?

Six electrons Signup and view all the answers

For most atoms, a stable configuration of electrons is attained when the atom _____.

Has eight electrons in its outermost shell. Signup and view all the answers

An atom that normally has _____ in its outer shell would not tend to form chemical bonds with other atoms.

Eight electrons Signup and view all the answers

When one or more pairs of valence electrons are shared by two neutral atoms, what type of bond is formed?

A covalent bond Signup and view all the answers

A polar covalent bond is a bond that _____.

Has shared electrons pulled closer to the more electronegative atom Signup and view all the answers

A covalent bond is likely to be polar if _____.

One of the atoms sharing electrons is much more electronegative. Signup and view all the answers

When the proton number and electron number are unequal, the atom or molecule _____.

Is an ion Signup and view all the answers

A sodium atom has a mass number of 23. Its atomic number is ______. How many electrons does it have if it is not an ion?

11 Signup and view all the answers

Copper has an atomic number of 29 and a mass number of 64. What would result if an uncharged copper atom lost two electrons?

The atomic number would remain 29, the mass number would remain 64, and the atom would be a cation with a +2 charge. Signup and view all the answers

The compound CaSO4 ionizes into a calcium ion and a sulfate ion (SO4). Calcium has two electrons in its outer shell. What would you expect the charge on the sulfate ion to be?

-2 Signup and view all the answers

Ionic bonds form as a result of _____.

Attraction between ions that have opposite charges. Signup and view all the answers

A hydrogen bond _____?

Is a weak chemical bond. Signup and view all the answers

What is the role of van der Waals interactions in biological molecules?

Although they are weak bonds, van der Waals interactions help to reinforce the three-dimensional shapes of large molecules. Signup and view all the answers

Which of the following molecules has the shape of a completed tetrahedron?

Methane (CH4) Signup and view all the answers

Pharmaceutical researchers are often interested in blocking particular receptor proteins on cell surfaces. What chemical property of a molecule would be most important for this type of application?

The molecule's shape Signup and view all the answers

Which of the following statements describes a reversible reaction that has reached chemical equilibrium?

The rate of the reverse reaction equals the rate of the forward reaction. Signup and view all the answers

Cells are surrounded by water, and cells consist of about 70 to 95% water. As a result, _____?

All of the listed responses are correct. Signup and view all the answers

Water is a polar molecule. This means that _____?

True Signup and view all the answers

The partial charges on a water molecule occur because of _____?

The unequal sharing of electrons between the hydrogen and the oxygen atoms of a water molecule. Signup and view all the answers

In a group of water molecules, hydrogen bonds form between _____?

The oxygen atom in one water molecule and a hydrogen atom in another water molecule. Signup and view all the answers

If water were not a polar molecule, how would the effects of global warming differ from what are currently observed or predicted to occur in the future?

The effects would be drastically worse because the loss of the polar nature of water would greatly reduce its specific heat and its ability to moderate temperature. Signup and view all the answers

The tendency of water molecules to stay close to each other as a result of hydrogen bonding _____?

All of the listed responses are correct. Signup and view all the answers

What do cohesion, surface tension, and adhesion have in common with reference to water?

All are properties related to hydrogen bonding. Signup and view all the answers

Most of water's unique features (for example, its versatility as a solvent, ability to moderate temperature, and cohesive behavior) result from the fact that _____?

Oxygen attracts electrons more than hydrogen does. Signup and view all the answers

The ability of water molecules to form hydrogen bonds with other water molecules and water's ability to dissolve substances that have charges or partial charges are _____?

Both caused by water's partial charges. Signup and view all the answers

Study Notes

Atomic Structure and Reactivity

Reactivity of an atom is mainly due to unpaired electrons in the valence shell.
A mole of different substances, such as table sugar and vitamin C, contains an equal number of molecules.
An uncharged nitrogen atom (atomic number 7) has 7 protons, 7 neutrons, and 7 electrons.

Chemical Reactions and Equilibrium

Equilibrium in a chemical reaction is achieved when the rates of forward and reverse reactions are equal.

Properties of Water

Water's ability to absorb heat is attributed to the breaking of hydrogen bonds, aiding in temperature regulation in living organisms.
Water is a polar molecule with opposite ends carrying partial charges, influencing its interactions and properties.
Hydrogen bonds between water molecules lead to cohesive and adhesive properties, essential for plant water transport and creating surface tension.

pH and Hydrogen Ion Concentration

A lake with a pH of 4.0 has a hydrogen ion concentration of 10^-4 M.

Isotopes and Atomic Mass

Isotopes of an element differ in atomic mass due to varying numbers of neutrons.
A specific carbon isotope with an atomic number of 6 and mass of 14 has 6 protons, 6 electrons, and 8 neutrons.

Chemical Bonds

Ionic bonds form from the attraction between oppositely charged ions.
Covalent bonds involve sharing valence electrons between atoms, potentially leading to polar covalent bonds if the atoms have different electronegativities.

Elements and Trace Elements

There are 92 naturally occurring elements, with trace elements, like copper, essential in small amounts for biological functions.
The four most abundant elements in living organisms are hydrogen, oxygen, nitrogen, and carbon.

Heat and Temperature Regulation

Water has a high specific heat, allowing it to moderate temperature changes, which is crucial for sustaining life.
Evaporative cooling and high heat of vaporization assist in temperature regulation.

Chemical Characteristics

Chemical behavior of elements is primarily determined by the number of electrons in the outermost shell.
Similarities in chemical reactivity among groups of elements stem from having similar outer-shell electron configurations.

Van der Waals Interactions

While weak, van der Waals interactions play a significant role in maintaining the three-dimensional structure of large biological molecules.

Liquid Water and Temperature Interactions

Water's unique characteristics, like its solvent properties and high specific heat, greatly contribute to various biological and ecological processes.

Adhesion and Cohesion

Cohesion leads to high surface tension in water, while adhesion enables water to interact with different substances.

Specific Heat and Temperature Change

The specific heat of a substance is the amount of heat needed to raise the temperature of 1 g by 1°C, impacting thermal regulation in biological systems.

Organism Temperature Regulation Change

If organisms were primarily composed of alcohol instead of water, temperature regulation systems would need to be more efficient due to alcohol's lower specific heat.### Molecular Cohesion
Molecular cohesion refers to the intermolecular attraction between similar molecules, contributing to the formation of surface tension in liquids.

Heat of Vaporization

The heat required to convert 1 g of a substance from liquid to gas is known as the heat of vaporization.

Specific Heat

Water's high specific heat moderates coastal climates, maintaining stable temperatures compared to more extreme inland climates.

Sweating and Cooling

Sweating cools the body due to water's high heat of vaporization, which absorbs significant heat from the body as it transitions from liquid to vapor.

Ice and Water Density

Ice floats because its molecules are farther apart in solid form than in liquid, making it less dense than liquid water.

Water as a Solvent

Water is a highly versatile solvent due to its polar nature, facilitating interactions with various ions and polar molecules.

Polarity and Solubility

Water's polarity allows it to form hydration shells around oppositely charged particles, enhancing its ability to dissolve ionic compounds like salt.

Hydrophobic Molecules

Nonpolar molecules that do not interact with water are termed hydrophobic and tend to cluster away from water.

Properties of Hydrophobic and Hydrophilic Substances

Hydrophilic substances possess charges or partial charges allowing water molecules to adhere, whereas hydrophobic substances do not have these characteristics and are repelled by water.

Cell Membrane Composition

Cell membranes are primarily made of hydrophobic molecules, which help separate internal cellular environments from external aqueous solutions.

Acid Definition

An acid is identified as a compound that donates hydrogen ions (H+) to a solution, thus lowering the pH.

Impact of Adding Acid to Solutions

Adding an acid increases the hydrogen ion concentration and lowers the pH of a solution.

Measuring H+ Concentration

A grapefruit juice at pH 3 contains ten times more H+ ions than tomato juice at pH 4.

pH and H+ Concentration Change

When pH shifts from 7 to 3, the hydrogen ion concentration increases by 10,000 times.

Buffers in Solutions

Buffers are substances that minimize changes in the concentration of H+ and OH- in a solution, maintaining pH stability.

Molar Mass and Concentration

To prepare a 2-molar (2 M) solution of sucrose (molecular mass 342 g), dissolve 342 g in water, adding water to reach a volume of 0.5 L.

Oceanic Carbon Dioxide Concerns

Increased CO2 uptake by oceans leads to more carbonic acid, causing a decrease in carbonate ion concentration, impacting marine ecosystems.

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Test your knowledge with these flashcards covering key concepts from Chapter 2 of Chemistry. These questions focus on atomic reactivity and the characteristics of chemical reactions. Perfect for students looking to reinforce their understanding of chemistry fundamentals.