Ch2/3 test

The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20kg of water how many degrees Celsius?

10.0 degrees Celsius

From its atomic number of 15, it is possible to predict that the phosphorus atom has

15 protons and 8 electrons in its outermost electron shell

If helium has an atomic mass of 4, and an atomic number of two, it is pretty safe to assume that it has how many neutrons?

2

Calcium has an atomic number of 20 and an atomic mass of 40. Therefore, a calcium atom must have

20 protons

What coefficients must be placed in the following blanks so that all atoms are accounted for in the products C6H12O6-->____C2H6O+____CO2

2;2

A moleclue of CO2 is formed when one atom of carbon (atomic #6) is covalently bonded with two atoms of oxygen (atomic #8). What is the total number of electrons that must be shared between the carbon atom and the oxygen atoms in order to complete the outer electron shell of all three atoms?

4

At what temperature is water at its densest?

4 degrees Celsius

You have two beakers. One contains a solution of HCl at pH=1.0. The other contains a solution of NaOH at pH=13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCl and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be

7.0

The unit of measurement (that honors the British scientist who helped develop the atomic theory around 1800) used to measure atoms, atomic particles, and molecules is the

Dalton (amu)

The nucleus of the atom found in the central region of the atom and is large and maintains the most of the nuclear mass. This is why the atom is often compared to a solar system with a large central sun (nucleus) and smaller planets (electrons) orbiting around it (T/F)

False

Which of the following best describes the relationship between the atoms described below? atom 1 atom 2 31 32 P P 15 15

They are both isotopes of phosphorus

Which of the following is a hydrophobic material?

Wax

A group of molecular biologists is trying to synthesize a new artificial compound to mimic the effects of a known hormone that influences sexual behavior. They have turned to you for advice. Which of the following compounds is most likely to mimic the effects of the hormone?

a compound with the same three-dimensional shape as part of the hormone

Sometimes atoms form molecules by sharing two pairs of valence electrons. When this occurs, the atoms are said to be joined by

a double covalent bond

The symbol "C" could potentially stand for both the element Carbon and

a single Carbon atom

Which of the following effects is produced by the high surface tension of water?

a water strider can walk across the surface of a small pond

Water's high specific heat is mainly a consequence of the

absorption and release of heat when hydrogen bonds break and form

A given solution contains 0.0001(10^-4) moles of hydrogen ions per liter. Which of hte following best describes this solution?

acidic: H+ donor

The smallest unit of matter that still retains the properties of an element is called

an atom

The number of protons in an atom (written as subscript to the left of the element symbol) is the

atomic #

The number that is used to distinguish the various elements (and orders them on the periodic table) is the

atomic #

Atoms whose outer electron shells contain eight electrons tend to

be stable and chemically nonreactive, or inert

The ionic bond of sodium chloride is formed when

chlorine gains an electron from sodium

If the pH of a solution is described from 9 to 8, it means that the

concentration of H+ ion has increased 10-fold compared to what it was at pH 9; concentration of OH- has decreased to 1/10 what it was at pH 9

A carbon atom is most likely to form what kind of bond (s) with other atoms?

covalent

What is the difference between covalent bonds and ionic bonds?

covalent bonds involve the sharing of electrons between atoms, and ionic bonds involve the transferring of electrons due to electrical attraction between atoms

If you are lacking one of the essential elements of the "disease" is called a(n)

deficiency

Which of the following would be regarded as compound(s)? a. H2 b. H2O c. O2 d. CH4 e. B and D, but not A and C

e. B and D, but not A and C

Nitrogen is much more electronegative than hydrogen. Which of the following statements is correct about the atoms in ammonia?

each hydrogen atom has a partial positive charge

Van der Waals interactions result when

electrons are not symmetrically distributed in a molecule

Which of the following solutions has the greatest concentration of hydrogen ions?

gastric juice at pH 2

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

hydrogen bond

Which of the following explains most specifically the attraction of water molecules to one another?

hydrogen bond

Why does ice float in liquid water?

hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water

If an atom has more neutrons than it would have at its "common elemental form," we would call it a(n)

isotope

Different atomic forms of an element contain the same number of protons but a different number of neutrons. What are these different atomic forms called?

isotopes

When two atoms are equally electronegative, they will interact to form

nonpolar covalent bonds

Hydrophobic substances such as vegetable oil are

nonpolar substances that repel water molecules

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

number of molecules

A covalent chemical bond is one in which

outer-shell electrons of two atoms are shared so as to satisfactorily fill the outer electron shells of both atoms

In a single molecule of water, two hydrogen atoms are bonded to a single oxygen atom by

polar covalent bonds

Based on your knowledge of the polarity of water molecules, the solute molecule is most likely

positively charged

If the nucleus of an atom is "decaying" spontaneously, giving off particles and energy, it would be a(n)

radioactive isotope

Which of the following solutions has the greatest concentration of hydroxyl ions?

seawater at pH 8

One of the buffers that contribute to pH stability in human blood is carbonic acid. Carbonic acid is a weak acid that dissociates into a bicarbonate ion and a hydrogen ion. Thus, H2CO3<-->HCO3+H+ If the pH of theblood drops, one would expect

the HCO3 to act as a base and remove excess H+ with the formation of H2CO3

Which of the following statements correctly defines a kilocalorie?

the amount of heat required to raise the temperature of 1kg of water by 1 degree Celsius

Which statement is true of all atoms that are anions?

the atom has more electrons than protons

Pure, freshly distilled water has a pH of 7. This means that

the concentration of H+ions in the water equals the concentration of OH- ions in the water

The reactivity of an atom arises from

the existence of unpaired electrons in the valence shell

Why are hydrocarbons insoluble in water?

the majority of their bonds are nonpolar covalent carbon-to-hydrogen linkages

A van der Waals interaction is the weak attraction between

the nucleus of one molecule and the electrons of a nearby molecule

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

the rate of the forward reaction is equal to the rate of the reverse reaction