Midterm 3 (practice questions)

The attractive interaction that holds atoms together in molecules

Chemical bond

A solid chunk of ice or a container filled with the same mass of water in the gaseous state. Which is more ordered? chunk of ice water in the gaseous state

Chunk of ice

A set of molecular orbitals so tightly spaced that the energies overlap each other.

Conduction band

An electron which is not focused around any one nucleus.

Delocalized electrons

In a bonding orbital between two atoms, where is the electron density the highest? (Where do you have the highest probability of detecting an electron?)

In between the two atoms

The chemical bond that binds metallic ions to nonmetallic ions by electrical attraction.

Ionic bonding

A process which goes in only one direction; its effects cannot be undone. Most processes which occur in nature are this way.

Irreversible process

A reversible process does what to the total disorder in the universe?

It does not change

If a certain LED (doped semi-conductor) is cooled in liquid nitrogen, the color moves to a higher frequency. What happens to the band gap?

It increases in energy

An refrigerator causes a cool place (the inside) to become colder, but at the same time heats up a warmer space. (A refrigerator blows hot air out the back into the room.) Which of the following correctly applies the law of increasing disorder to a refrigerator?

It is true that the heat flow from the cold region to the hotter region increases order, but this is made up for by increasing the disorder of energy from another source.

How does a catalyst affect a reaction?

It lowers the activation energy

The geometry around a carbon atom with a triple bond

Linear

The ability of atoms to change relative position without weakening the bonds between them.

Malleability

Positive nuclei surrounded by a "sea" of electrons.

Metallic bonding

Which of the following is a correct comparison of metals and semi-conductors?

Metals' resistance increases when temperature increases while a semi-conductors resistance decreases.

The structural organization of water.

Molecular substances

Which of the following is atomic matter rather than molecular or network matter?

Neon gas

Which of the following tends to have the highest melting and boiling points?

Network matter

Property of absorbing photons throughout the electromagnetic spectrum.

Opacity

Which of the following is not a compound?

Oxygen molecule

Which of the following pairs of metals is most likely to form alloys of all proportions? Cs and In Pb and K Pt and Au

Pt and Au

A chamber with two compartments, one containing pure oxygen and the other containing pure nitrogen or the same chamber in which the two gases have been allowed to mix. Which is more ordered? pure oxygen the mixed chamber

Pure oxygen

How easily light bounces off the surface of a substance.

Reflectivity

A measure for how difficult it is to make a current move through a substance.

Resistibility

A process which naturally occurs equally well forward or backwards.

Reversible process

A substance formed from the ionic bond of a metal with a nonmetal.

Salt

Substances that conduct electricity better than insulators but not as good as conductors.

Semiconductors

Locate the elements palladium (Pd, atomic #46) and nickel (Ni, atomic #28) on the periodic table. If Pd is combined with Ni, which of the following characteristics will the product show at room temperature?

Shiny, malleable solid.

Which of the following pairs of metal is most likely to form alloys of all compositions? Ba and Ga Sn and Pb Li and Bi

Sn and Pb

Which is the best definition of an alloy?

Solid mixture of metals

The gasoline engine of an automobile is considerably less than 100% efficient. This means that not all of the energy in the gasoline is turned into kinetic energy of the car. Which of the following best explains why?

Some of the chemical potential energy in the gasoline must become ambient thermal energy if the rest is to supply the kinetic energy of the automobile. This means some energy must be wasted.

Everything outside what we have defined to be the system.

Surroundings

A small piece of the world around which we mentally draw a box and upon which we focus our attention.

System

If analyzing a fridge in relationship to its surroundings, what would the fridge be considered?

System

The geometry around a carbon atom with four single bonds.

Tetrahedron

Disorder in the universe increases or stays the same anytime a process occurs.

The Law of Increasing Disorder

Which of the following is the best description of activation energy?

The energy that must be put into a system before a reaction can take place.

An refrigerator causes a cool place (the inside) to become colder, but at the same time heats up a warmer space. (A refrigerator blows hot air out the back into the room.) A refrigerator is normally run with its door closed. What would happen if the refrigerator were placed in the middle of a closed room with its door open and turned on?

The room would heat up because all of the energy absorbed by the refrigerator, both thermal and electrical potential, is released back into the room as thermal energy.

The degree to which a substance conducts heat.

Thermal conductivity

A temporary product of a chemical reaction that typically has more chemical potential energy than either the reactants or the final products.

Transition state

(T/F) A reaction usually goes faster at higher temperatures.

True

(T/F) An energetically favorable reaction gives off heat.

True

(T/F) Bonding MOs have electron energies that are lower than electron energies for unbound valence electrons.

True

(T/F) Compounds containing transition metals are often brightly colored.

True

(T/F) Electrons in a bonding molecular orbital are most likely to be found between the nuclei in a molecule.

True

(T/F) Energy and entropy are both involved in chemical reactions.

True

(T/F) Gravitational potential energy is a more ordered form of energy than electrical potential energy.

True

(T/F) Light can only be seen through metal that is so thin it is only a few atoms thick.

True

(T/F) Metals do not have a band gap.

True

(T/F) Metals do not let light through.

True

(T/F) Metals have a greater tendency than non-metals to lose electrons.

True

(T/F) Semiconductors conduct better at higher temperatures.

True

(T/F) Sodium chloride (NaCl) and Magnesium (Mg) are examples of network substances.

True

How do semiconductors change with increasing temperatures?

When you heat them up, semiconductors act more like metals.

The energy that must be put into a system before a reaction can take place.

Activation energy

Metal-metal compound.

Alloy

Compounds between two different metals are called

Alloys

Which of the following processes is closest to an ideal reversible process?

An ice cube floating in a glass of water at zero degrees.

The high energy orbital of the pair of MO's formed when two atomic orbitals combine.

Anti-bonding orbital

The structural organization of Group 8A elements.

Atomic matter

The low energy orbital of the pair of molecular orbitals (MO's) formed when two atomic orbitals combine.

Bonding orbital

The substance most likely to be a pure element is

copper

In an irreversible process, the overall disorder of the universe

increases

An ice cube melts in a glass of warm water. This is an example of which type of process?

irreversible

A large, solid chunk of table salt and a beaker of pure water or a solution made by mixing the salt and water together. Which is more ordered? salt water solution pure water and pure salt

pure water and pure salt

Overall disorder remains unchanged in

reversible processes

Of the quantities listed, the one associated with the most disorder is hemical potential energy. gravitational potential energy. macroscopic kinetic energy. nuclear potential energy. thermal energy in a glass of water.

thermal energy in a glass of water.

(T/F) The energies of the orbitals that form when metals interact are very widely spaced in energy.

False

(T/F) The probability waves (orbitals) that describe the possible locations for an electron in a molecule are exactly the same as those for an electron in an isolated atom.

False

Which type of energy is the most ordered?

Gravitational potential energy

Each molecule of nitric acid has the formula HNO3. If there are 6000 oxygen atoms present and 6000 nitrogen atoms present, how many hydrogen atoms will be required to convert all of the oxygen atoms into nitric acid?

2000

The Law of Increasing Disorder places limits on the efficiency of energy conversion. Which of the following is allowed?

100% conversion of any other form of energy into ambient thermal energy.

The 2nd Law of Thermodynamics (Law of Increasing Disorder) places limits on the efficiency of energy conversion. Which of the following is allowed?

100% conversion of electricity to ambient temperature thermal energy.

Two or more different elements that are chemically combined are always

A compound

A metal can best be described as which of the following?

A network solid consisting of positively charged atoms in a sea of electrons

A quantitative measure of disorder. It increases as the disorder increases

Entropy

In order for a chemical reaction to occur:

Entropy must increase as a result of the reaction.

The point in a chemical reaction in which the forward and reverse reaction rates are equal.

Equilibrium

The structural organization of salts and metals.

Extended or network substances

(T/F) A catalyst is a chemical that is present at the beginning of a reaction but not at the end.

False

(T/F) A salt shaker and a pepper shaker get knocked off the table and spill onto the floor. If you collected every last grain of salt and pepper and separated them back into their shakers this can be considered a reversible process.

False

(T/F) A very fast reaction has a very high activation energy.

False

(T/F) Alloys have a higher conductivity

False

(T/F) An increase in temperature also means that disorder increases.

False

(T/F) Compositions of alloys are generally fixed in simple ratios.

False

(T/F) For an alloy to form, the atoms must be different sizes.

False

(T/F) From our current understanding, sometime in the future engineers will design a car that is completely efficient, i.e., a car that creates no additional disorder in the universe.

False

(T/F) In a chemical formula, subscripts are placed to the left of the chemical symbol to indicate the number of that type of atoms in a molecule.

False

(T/F) In the future, engineers will be able to design a car that is turns 100% of the energy in the gasoline into kinetic energy.

False

(T/F) Irreversible processes are always spontaneous and occur on their own without any intervention.

False

(T/F) Mass spectrometry provides information about the energy associated with motions within molecules.

False

(T/F) Metals conduct better at higher temperatures.

False

(T/F) Metals have higher ionization energies than non-metals do.

False

(T/F) Molecular orbitals are the same shape as atomic orbitals.

False

(T/F) Molecular substances melt at very high temperatures.

False

(T/F) Often alloys are better conductors than either of the metals, in their pure form, that make up the alloy.

False

A balloon filled with helium at room temperature at sea level or the same balloon at an altitude of 8000 feet where the air is colder. Which is more ordered? balloon at 8000 feet balloon at sea level

balloon at 8000 feet

in the upper atmosphere (also known as the ozone hole). As a catalyst, Cl may

be lowering the activation energy of some reaction involving ozone.

An auto engine cannot convert all of its fuel's chemical potential energy into macroscopic kinetic energy because

disorder would be decreased.

Complete conversion of one form of energy to another can occur only in the direction

from higher to lower organized forms