Chem 100 Exam 2

How many moles of sodium chloride are there in 250 mL of a 1.20 M sodium chloride solution? a) 0.30 b) 0.60 c) 1.2 d) 2.4

0.30

If the lead concentration in water is 1 ppm, then we should be able to recover 1 mg of lead from _____ L of water. a) 0.01 b) 0.1 c) 1 d) 10

1

What is the molarity of sodium chloride in a solution containing 0.50 mol of sodium chloride in 500 mL of water? a) 0.25 M b) 0.50 M c) 1.0 M d) 5.0 M

1.0 M

What percentage of a radioactive isotope would remain after three half-lives? a) 6.3% b) 12.5% c) 25.0% d) 50.0%

12.5%

A 4-L sample of water contains 80 µg of lead. What is this lead concentration, in parts per billion (ppb)? a) 20 b) 80 c) 320 d) 500

20

If you have 200.0 g of radioisotope with a half-life of 5 days, how much isotope would remain after 15 days? a) 12.5g b) 13.3g c)25.0g d) 40.0g

25.0g

The half-life of carbon-14 is 5,730 years. If you started with 100.0 g of carbon-14, how much would remain after 4-half lives? a) 25.0g b) 12.5g c) 6.25g d) 57.3g

6.25g

A student wants to prepare exactly 250 mL of a 0.500 M aqueous potassium hydroxide solution. What mass of potassium hydroxide (molar mass = 56.10 g/mol) must the student dissolve in the 250 mL of solution? a) 56.1g b) 28.1g c) 14.0g d) 7.01g

7.01g

What percentage of Earth's water is in the oceans? a) 97% b) 50% c) 3% d) 0.014%

97%

The drawing shows two water molecules. Which statement is correct? a) A: covalent bond; B: hydrogen bond; B is stronger b) A: hydrogen bond; B: covalent bond; A is stronger c) A: covalent bond; B: hydrogen bond; A is stronger d) A: hydrogen bond; B: covalent bond; B is stronger

A: covalent bond; B: hydrogen bond; A is stronger

Which correctly describes groundwater? a) Any fresh water found above ground in lakes and rivers; usually needs treatment to remove harmful contaminants b) Any water found above ground in lakes and rivers; usually free of harmful contaminants c) Any water taken from aquifers d) None of these choices are correct

Any water taken from aquifers

In this photovoltaic (solar) cell, the n-type semiconductor is in the region labeled a) A b) B c) C d) D

B

Which compound is insoluble in water? a) Sodium carbonate b) Potassium nitrate c) Ammonium chloride d) Calcium carbonate

Calcium carbonate

In this electrochemical cell, the reduction half reaction is a) Cu2+(aq) + 2 e¯ → Cu(s) b) Zn(s) → Zn2+(aq) + 2 e¯ c) Zn(s) → Cu(s) d) Cu2+(aq) → Zn2+(aq)

Cu2+(aq) + 2 e¯ → Cu(s)

Which covalent bond is the most polar? a) H — H b) H — O c) H — N d) H — S

H — O

Which chemical equation shows the dissociation of two protons from trihydrogen phosphate (phosphoric acid)? a) H3PO4 → H 2++ HPO4¯ b) H3PO4 → H 22++ PO4 2¯ c) H3PO4 → 2H+ + HPO4 2¯ d) H3PO4 → H 33+ + PO43¯

H3PO4 → 2H+ + HPO4 2¯

Which reaction most accurately represents the dissociation of nitrous acid (HNO2) in water? a) HNO2 + H2O → H3O+ + NO2¯ b) HNO2 + H2O → H3O2+ + NO¯ c) HNO2 + H2O → HN + HO+ + HO2¯ d) HNO2 + H2O → H3O+ + N + O2¯

HNO2 + H2O → H3O+ + NO2¯

Which compounds are not soluble in water at room temperature? a) I and II only b) II and III only c) III and IV only d) I and IV only

I and II only

Which argument(s) for the increasing use of solar energy is/are valid? I. Solar cells are becoming cheaper and increasingly more efficient II. The cost of generating electricity from fossil fuels is increasing III. Limited and uncertain supply and the increasing requirements for pollution control are raising the cost of using fossil fuels a) I and III only b) I, II and III

I, II and III

What sort of energy is associated with energy from wind? a) Potential energy b) Thermal energy c) Kinetic energy d) Chemical energy

Kinetic energy

Which chemical equation shows the dissociation of magnesium hydroxide? a) Mg(OH)2 → Mg2+ + 2OH¯ b) MgOH → Mg2+ + OH2¯ c) Mg(OH)3 → Mg3+ + 3OH¯ d) Mg(OH)2 → Mg2+ + H2O + O2−

Mg(OH)2 → Mg2+ + 2OH¯

Mixing which of the following will produce a precipitation reaction (give an insoluble product)? a) HNO3 (aq) and Sr(OH)2(aq) b) LiNO3 and NaI c) Na2SO4(aq) and Ba(OH)2(aq) d) NaOH and KBr

Na2SO4(aq) and Ba(OH)2(aq)

What condition must be met for a battery to be rechargeable? a) Either its anode or its cathode must generate a gas as a result of the electrochemical reaction b) It must generate electricity via an acid-base reaction rather than via an oxidation-reduction reaction c) The battery must be open to the outside so that it can vent any internal pressure that builds up from gases within it d) The electrochemical reaction of the battery must be reversible

The electrochemical reaction of the battery must be reversible

How is wind energy related to the Sun? a) It has no relation b) Wind turbines need solar panels to operate correctly c) The heat of the Sun drives large-scale movements of air d) Wind turbines only operate during daylight hours

The heat of the Sun drives large-scale movements of air

A 0.25 M aqueous solution of potassium chloride, KCl, is tested for conductivity using the type of apparatus shown. What do you predict will happen? a) The bulb will not light up - KCl is a nonelectrolyte b) The bulb will not light up - KCl is in the molecular form when dissolved in water c) The light bulb will shine dimly - KCl is only partially ionized in aqueous solution d) The light bulb will shine brightly - KCl is highly ionized in aqueous solution

The light bulb will shine brightly - KCl is highly ionized in aqueous solution

Why can the lead-acid batteries used in cars generate electricity for several years before running down? a) A lead-acid battery is so large that it holds large quantities of the chemicals whose electrochemical interaction creates the electricity b) The mechanical motion of the engine drives an alternator that generates electricity to recharge the battery

The mechanical motion of the engine drives an alternator that generates electricity to recharge the battery

What is the primary determinant of the voltage developed by a battery? a) The nature of the materials in the reaction b) The age of the battery c) The overall size of the galvanic cells d) The size of the electrodes

The nature of the materials in the reaction

Which is the best definition of specific heat? a) The quantity of heat energy that must be absorbed to cause one gram of a liquid substance to boil b) The quantity of heat energy that must be absorbed to increase the temperature of one gram of a substance one degree Celsius c) The boiling point of a liquid substance in degrees Celsius

The quantity of heat energy that must be absorbed to increase the temperature of one gram of a substance one degree Celsius

Which is the cathode in this galvanic cell? a) The solid zinc electrode b) The Zn2+(aq) ions in the 1 M solution c) The solid silver electrode d) The Ag+(aq) ions in the 1 M solution

The solid silver electrode

Which is an oxidation half-reaction? a) 2 H2 + O2 → 2 H2O b) Zn → Zn2+ + 2 e¯ c) 2 HCl + Ba(OH)2 → 2 H2O + BaCl2 d) Cl2 + 2 e¯ → 2 Cl¯

Zn → Zn2+ + 2 e¯

Which is the best representation showing a sodium cation in water? a) a b) b c) c d) d

a

Chemical energy is converted directly into electrical energy in a) a galvanic cell. b) an electrical power plant. c) an electrolytic cell. d) an automobile's engine.

a galvanic cell.

The "doping" of a semiconductor to improve its performance means a) mixing large amounts of a metal with small amounts of a semiconductor so that the metal itself becomes a semiconductor. b) adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal.

adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal.

The "doping" of a semiconductor to improve its performance means a) mixing large amounts of a metal with small amounts of a semiconductor so that the metal itself becomes a semiconductor. b) adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal. (REPEAT QUESTION FROM #29!)

adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal.

The diagram below shows a simplified version of a fractionating column used in the petroleum industry. The compounds that are obtained at position D are a) asphalt b) gasoline c) jet fuel d) refinery gases

asphalt

The general term for plant matter such as trees, grasses, argricultral crops, or other biological material is a) biomass b) cornstarch c) diesel d) fossil fuel

biomass

Which shows the Lewis structure of water with the correct partial charges and nonbonding electrons? a) a b) b c) c d) d

c

What atmospheric component is responsible for the natural acidity of rain? a) nitrogen b) ozone c) oxygen d) carbon dioxide

carbon dioxide

Given this diagram, this semiconductor is a) made of pure silicon. b) carrying an extra electron. c) missing an electron. d) excited by a photon.

carrying an extra electron.

Smokestacks at these plants release sulfur oxides and carbon dioxide into the air: a) coal-burning plants b) nuclear plants c) coal-burning and nuclear plants d) none of theses choices are correct

coal-burning plants

Which feature or process is unique to nuclear power plants when compared to conventional coal-burning power plants? a) formation of steam b) smoke stacks c) steam turbines d) control rods

control rods

Complete the following statement while ignoring any thermodynamic considerations. A candle may be considered a more efficient producer of light than a flashlight because it a) converts chemical energy directly into light. b) produces more heat than a flashlight. c) does not have a battery to recharge or replace. d) may be used in remote locations far from electrical networks or power lines.

converts chemical energy directly into light.

Which best symbolizes the hydrogen bonding between two water molecules? a) a b) b c) c d) d

d

The process by which a solution is heated to its boiling point and the vapors are condensed and collected is known as a) combustion b) cracking c) crystallization d) distillation

distillation

The first law of thermodynamics states that a) energy is the capacity to do work b) doing work is defined as causing movement against a resisting force c) heat flows from a warmer body to a cooler body d) energy is neither created nor destoryed

energy is neither created nor destoryed

In a refinery, the components of petroleum are separated by a) combustion reactions b) crystallization c) fractional distillation d) isomerization

fractional distillation

Which example is both a type of nuclear radiation and electromagnetic radiation? a) microwave radiation b) gamma radiation c) alpha rays d) ultraviolet radiation

gamma radiation

Which is produced in the greatest amount from a barrel of petroleum a) asphalt and road oil b) gasoline c) home heating oil d) lubricants and waxes

gasoline

In general, a modern plug-in hybrid vehicle is less polluting than a standard vehicle because it runs on both a a) gasoline engine and an electric motor run by a rechargeable battery. b) gasoline engine and a fuel cell. c) fuel cell and an electric motor run by a rechargeable battery. d) gasoline engine and a cleaner diesel engine

gasoline engine and an electric motor run by a rechargeable battery.

The energy that flows from a warmer body to a colder body is called a) heat b) temperature c) potential d) work

heat

How is heat energy used to generate electricity in a modern power plant? a) heat warms wires casuing electrons to move through them more rapidly b) heat boils water to make steam, which drives a turbine c) heat warms the fins on a turbine, causing them to spin

heat boils water to make steam, which drives a turbine

In an exothermic chemical reaction a) the mass of the products is greater than the mass of the reactants b) the mass of the products is less than the mass of the reactants c) heat is released as the reactions proceeds d) heat is absorbed as the reaction proceeds

heat is released as the reaction proceeds

petroleum (crude oil) is a complex mixture of thousands of substances, the majority of which are a) carbohydrates b) hydrocarbons c) natural gases d) proteins

hydrocarbons

The attractions between anions and cations throughout a crystal are known collectively as a) covalent bonds b) polar covalent bonds c) hydrogen bonds d) ionic bonds

ionic bonds

Electronegativity a) is a measure of an atom's attraction for an electron in a chemical bond. b) is the total negative charge on a polyatomic anion. c) is the same for all of the elements in a family or group. d) decreases from left to right across a period on the periodic table.

is a measure of an atom's attraction for an electron in a chemical bond.

Any chemical or physical change that absorbs energy a) has high activation energy b) is an endothermic process c) is an exothermic process d) is a catalyzed process

is an endothermic process

In the petroleum industry, what does a refinery do? a) it separates crude oil into fractions consisting of compounds with similar boiling points b) it separates crude oil from the coal which is is almost always found c) It produces the machinery by which crude oil is removed from the ground

it separates crude oil into fractions consisting of compounds with similar boiling points

The heat energy released or absorbed by a chemical reaction is generally determined by the difference between the energy that a) must be put in to break the bonds in the reactants and the energy that must be put in to make the bonds in the products. b) must be put in to break the bonds in the reactants and the energy that is released upon making the bonds in the products.

must be put in to break the bonds in the reactants and the energy that is released upon making the bonds in the products.

Which is a fossil fuel? a) wood b) uranium c) ethanol d) natural gas

natural gas

During the chemical reaction in an electrochemical cell, a) a substance is oxidized and gains electrons. b) electrons travel from the cathode to the anode. c) oxidation takes place alone, without an accompanying reduction d) oxidation occurs at the anode.

oxidation occurs at the anode.

Combustion is a chemical process in which a fuel combines with ________ to release energy and form products. a) nitrogen b) oxygen c) methane d) hydrogen

oxygen

Sunlight (solar radiation) may be turned directly into electricity using ______ cells. a) fuel b) photovoltaic c) electrolytic d) lead-acid

photovoltaic

The energy stored in the chemical bonds of fossil fuels is a form of ________ energy. a) electrical b) mechanical c) potential d) kinetic

potential

The current through a wire is most closely related to the a) energy of the electrons flowing through the wire b) type of electrons flowing through the wire. c) rate of electron flow through a wire. d) oxidation potential of the electrons flowing through the wire.

rate of electron flow through a wire.

The fact that carbon (C) is less electronegative than nitrogen (N) means that in a C — N bond, the a) shared electrons are closer to the C atom than to the N atom. b) shared electrons are closer to the N atom than to the C atom. c) C atom takes the electrons from the N atom forming C¯ and N+. d) N atom takes the electrons from the C atom forming C+ and N¯.

shared electrons are closer to the N atom than to the C atom.

Over the very long run, the energy source that has the greatest potential to meet humanity's needs is a) coal b) hydropower c) renewable biomass d) solar (the sun)

solar (the sun)

Whenever a substance is oxidized, a) it is called the oxidizing agent. b) some other substance must be reduced. c) it gains electrons. d) hydronium ions are produced.

some other substance must be reduced.

Fission is the process of creating energy by a) combining small nuclei to form a larger, more stable nucleus b) combining small nuclei to form a larger, less stable nucleus c) splitting large nuclei to form smaller, more stable nuclei d) splitting large nuclei to form smaller, less stable nuclei

splitting large nuclei to form smaller, more stable nuclei

Which is a common characteristic of both nuclear and conventional electric power plants? a) smoke stacks b) fuel rods c) controls rods d) steam turbines

steam turbines

The property of matter that determines the direction of heat flow is the a) mass b) temperature c) volume d) density

temperature

In an electrochemical cell, the anode is a) the electrode at which oxidation takes place. b) the material used to connect the two half cells to each other. c) always used up before the cathode. d) never a metal.

the electrode at which oxidation takes place.

Semiconductors are more effective than metals as converters of solar radiation into electricity because a) it is easier for the atoms of a semiconductor to absorb solar energy and to move from place to place within the solid, thereby conducting electricity. b) the energy contained in sunlight gives the valence electrons in the semiconductor atoms the extra energy they need to "flow" throughout the solid.

the energy contained in sunlight gives the valence electrons in the semiconductor atoms the extra energy they need to "flow" throughout the solid.

A polar covalent bond is created when a) a metallic element reacts with a nonmetallic element. b) two atoms share their bonding electrons unequally. c) two atoms share three or more electrons. d) two atoms of the same element form double or triple bonds.

two atoms share their bonding electrons unequally.

Which source of renewable energy has seen the greatest growth in the last decade? a) wind b) Photovoltaic c) Hydroelectric d) Biodiesel

wind