CHM 1020 Final

Which vibrational mode for carbon dioxide is not expected to contribute to the greenhouse effect?

*Remember that vibrations that cancel each other out do not contribute to warming.

Free radicals are

- species with unpaired electrons - species such as H• and •OH - highly reactive chemical species.

Assume that coal can be represented by the chemical formula C135H96O9NS. If 15.0 tons of coal is burned, what mass of sulfur is formed in the SO2 produced by this process?

0.252 tons

How many moles of sodium chloride are there in 250 mL of a 1.20 M sodium chloride solution?

0.30

Calculate the mass of 2.50 × 104 molecules of nitrogen gas.

1.16 × 10¯18 g *Remember that one mole is 6.02 × 1023 items and that nitrogen is diatomic.

There are approximately 2 × 1022 molecules and atoms in each breath we take and the concentration of CO in the air is approximately 9 parts per million. Approximately how many CO molecules are in each breath we take?

1.8 × 10^17

There are approximately 2 × 10^22 molecules and atoms in each breath we take and the concentration of CO in the air is approximately 9 parts per million. Approximately how many CO molecules are in each breath we take?

1.8 × 10^17

How many oxygen atoms are in 6.02 x 1023 molecules of ozone?

1.81 x 1024 O atoms

Calculate the pH of a solution prepared by dissolving 1.2 g of potassium hydroxide (KOH) in 1,250 mL of water.

12.23 *Find the hydroxide ion concentration, then the pOH then take 14 - pOH = pH.

How many cm are in 0.129 m?

12.9 cm

The nuclear fission of 235U can occur via a number of different pathways. If 3 neutrons and 89Se are produced, what is the other fission product?

144Ce

The nuclear fission of 235U can occur via a number of different pathways. If 2 neutrons and 90Rb are produced, what is the other fission product?

144Cs

Choose the proper coefficients for each substance to yield a balanced equation.

2, 1, 2 *make sure that the total number of each element is the same on both sides of the equation.

If 1.8 × 10^14 J is released in a nuclear reaction, how much matter was lost?

2.0 × 10^¯3 kg *E = mc2 where c = 3.0 × 10^8 m/s.

A coal-burning power plant generates 6.0 x 1016 J per year. If the combustion of coal yields 29 kJ/g, how many grams of coal was burned each year?

2.1 x 1012 g

Which of the following would be described as "fine particles?"

2.5 μm diameter soot *remember that these are solids and not gases

What is the mass of exactly 500 sulfur atoms?

2.66 × 10¯20 g *Remember that one mole is 6.02 × 1023 items and one sulfur has a molar mass of 32 g/mole.

A Big Mac® has a nutritional value of 563 Calories. Assuming that all the energy produced from consuming the burger goes towards keeping your heart beating, approximately how many days can the Big Mac sustain a heartbeat of 82 beats/minute? (Note: 1 Cal = 1000 cal, 1 cal=4.184 J, 1 heartbeat requires 1 J of energy)

20 days

What is the balanced chemical equation for the complete combustion of ethane (C2H6) to produce carbon dioxide and water?

2C2H6 (g) + 7O2 (g) ⟶4CO2 (g) + 6H2O (g)

Numbers 1 through 4 are used to identify four different elements. Based on periodic table trends, which number identifies the element that is expected to have the greatest tendency to attract a shared pair of electrons?

3

Hydrogen gas (H2) is a promising alternative to fossil fuels. How many molecules are present in 1.0 kg of hydrogen gas?

3.0 × 1026 *Remember that one mole is 6.02 × 1023 items and that hydrogen has a molar mass of 2.016 g/mole.

Although coal is a complex mixture of substances, its elemental composition can be approximated by the formula C135H96O9NS. Using this formula, predict the amount of CO2 released from the combustion of 1.00 × 106 metric tons of coal (about the annual average for a coal-fired power plant). 1 metric ton = 1 ×103 kg.

3.11 × 109 kg *Remember that you will have to write and balance a combustion equation for coal.

The heat of combustion of butane (C4H10) is 91.4 kJ/g. How much heat is produced if 7.0 moles of butane undergoes complete combustion?

3.7 x 104 kJ

The recommended daily requirement of calcium is 1,000 mg. Tap water in a Midwestern city contains approximately 150 mg Ca/L. A person living in the city who drinks two liters of water in one day would receive ________ percent of his/her RDA of calcium.

30 *Use the concentration times the volume to get the total consumption, then divide by 1000 to get a percent.

What is the frequency of light with a wavelength of 634 nm?

4.73 x 10^14 Hz

As of 2007, what is the maximum efficiency of a multijunction solar cell?

40 percent

Consider the following equation that describes the complete combustion of propane, C3H8. The bond energies are: C H 416 kJ/mol; C C 356 kJ/mol; OO 498 kJ/mol; CO 803 kJ/mol; H O 467 kJ/mol. Which is the total amount of energy required to break all of the bonds in propane?

4040 kJ/mol

Find the molar mass of ethanol, C2H6O.

46.07 g/mol

In a 45 minute road trip a vehicle emitted 16.7 g of nitrogen dioxide (NO2) from its exhaust. What is the mass of nitrogen atoms in this amount of NO2?

5.08 g

Yellow light has a wavelength of 580 nm. What is the frequency of this light?

5.17 × 1014 s¯1 *remember that wavelength is in meters and c = 3.0 × 108 m/s.

The heat of combustion of ethane, C2H6, is 1560 kJ/mol. What is the heat of combustion of ethane, in kJ per gram?

51.9 kJ/g

The isotope 48Ti is produced by the alpha decay of which of the following?

52Cr

The heat of combustion for n-heptane is 4,187 kJ/mol. How much heat is produced if 200 kg of n-heptane (C7H16) is completely combusted?

8.36 x 106 kJ

The heat of combustion of methane, CH4, is 50.1 kJ/g. How much heat would be generated if 1.00 mol of methane undergoes complete combustion?

804 kJ

What is the mass percent of carbon in octane (C8H18)?

84 %

Consider the following equation that describes the complete combustion of propane, C3H8.The bond energies are: C H 416 kJ/mol; C C 356 kJ/mol; OO 498 kJ/mol; CO 803 kJ/mol; H O 467 kJ/mol. Which is the amount of energy gained on making all the bonds in carbon dioxide and water according to the equation?

8554 kJ/mol *Remember to take the sum of all bonds formed minus all broken. Take the stoichiometric coefficients into account.

The quantity 8.7 × 105 g expressed in standard decimal notation.

870,000 g *positive power of ten move the decimal to the right.*

How much energy is equivalent to 1.0 × 10¯4 kg of matter? (Speed of light = 3.0 × 108 m/s)

9.0 × 1012 J *E = mc^2 where c = 3.0 × 10^8 m/s.

Which one of the following is an example of a homogeneous mixture?

A glass of pulp-free lemonade

In which example is the entropy of the initial state lower than the entropy of the final state?

A pot of water boils to produce water vapor at 100°C *Remember that this means going to a state of more order.

The drawing shows two water molecules. Which statement is correct?

A: covalent bond; B: hydrogen bond; A is stronger *Remember that covalent bonds are a sharing of electrons while hydrogen bonds are more like attractions between molecules.

Which of the following is the chemical symbol for silver?

Ag

An inversion layer happens when a certain weather pattern traps cooler air near the surface of the earth with a warmer air mass above it. Why is this a problem?

Air pollution concentrates in the inversion layer

Which naturally occurring radioactive particles are the size of a helium nucleus?

Alpha particles

What metal is used to dope an n-type semiconductor?

Arsenic *Silicon can't be doped with itself and only one of these has one more electron than silicon.

Which of these represents the best Lewis structure for acetylene (C2H2)?

B *Remember that you must use all the valence electrons and give all the atoms an octet (except hydrogen with a duet).

Why is the mileage a vehicle gets less when burning E85 than 100 percent gasoline?

Ethanol has a lower heat of combustion *Remember that it is the amount of energy that comes from the fuel that determines how much work can be done.

Which is produced in the greatest amount from a barrel of petroleum?

Gasoline *This is the main component used to run automobiles and trucks.

HCFCs have been developed to replace CFCs as refrigerants. Which property of these new compounds makes them environmentally superior to CFCs?

Greater reactivity leads to decomposition at elevations below the stratospheric ozone concentration maximum *it is the stable compounds of chlorine that caused the ozone hole in the first place.

Which covalent bond is the most polar?

H — O *Find the one with the largest difference in electronegativities.

Which is the balanced chemical equation showing hydrogen peroxide (H2O2) decomposing into hydrogen (H2) and oxygen (O2)?

H2O2 → H2 + O2

Which is the correct Lewis structure?

H:Cl: (: above Cl, : below Cl as well) --> all atoms must have an octet but hydrogen may only have 2 electrons

Which of the following compounds is useful for putting out fires and does not deplete stratospheric ozone concentrations?

Halon-1211

How is heat energy used to generate electricity in a modern power plant?

Heat boils water to make steam, which drives a turbine

Which square(s) contain(s) only one or more compounds?

I 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

I, II and III *As our energy needs increase and both global dynamics and pollution control needs change, there is a place for solar energy in the mix.

Which increases the efficiency of a photovoltaic or solar cell? I. Replacing crystalline silicon with its non-crystalline form II. Increasing the number of alternating p- and n-type layers of semiconductors III. Decreasing the thickness of each alternating p- and n-type layer of semiconductor

I, II, and III *There are many ways to increase efficiency, although they are not easy to accomplish in an industrial setting.

Which diagram(s) best represent(s) only individual atoms?

III only *the atoms are not bound to other atoms

Where is most of the carbon on earth stored?

In the form of fossil fuels and carbonate minerals and rocks

Which is not a benefit associated with nuclear power plants?

Inexpensive to operate *The benefits and drawbacks of nuclear power are basically the opposite of other methods of producing power.

Which is not a known advantage of natural gas over other fossil fuels?

It is far more abundant than any other fossil fuel *Remember that natural gas is usually found with oil but it is made of fairly small molecules.

Predict the products of this reaction: KOH + HNO3 →

KNO3 + H2O *Acid and base make a salt and water.

In a solar cell, semiconductors of the p-type and n-type are placed in contact with each other via a conducting wire. In order to generate an electric current, which of the following must be true?

Light shining on the system must have enough energy to set electrons in motion from the n-type semiconductors to the p-type

In which example is the entropy of the initial state greater than the entropy of the final state?

Liquid water freezes into ice *Remember that an increase in entropy means an increase in disorder in the system.

Which concentration is consistent with a basic solution?

MOH- = 3.4 × 10^-3 M

What is the primary component of an exhaled breath?

N2

Which is the balanced chemical equation for the reaction of nitrogen (N2) with oxygen (O2) to form NO?

N2 + O2 → 2 NO *make sure that the total number of each element is the same on both sides of the equation.

A proton released by an acid in aqueous solution quickly reacts with water to form a hydronium ion. What product is formed when a proton reacts with ammonia (NH3)?

NH4+ *Just add the hydrogen and its charge to the ammonia molecule.

Mixing which of the following will produce a precipitation reaction (give an insoluble product)?

Na2SO4(aq) and Ba(OH)2(aq) *Swap the positive and negative ions to have the other partner then see if that is a soluble product.

What weighs more; 6.022 x 1023 molecules of water (H2O), 6.022 x 1023 molecules of methane (CH4), 6.022 x 1023 molecules of ammonia (NH3) or 6.022 x 1023 molecules of nitrogen monoxide (NO)?

Nitrogen monoxide

Which two gases make up more than 95 percent of an inhaled breath?

O2 and N2 *think about the two main components of the atmosphere

Which one of the following compounds is considered to be a molecular compound?

PCl3

Which type of renewable energy has most commonly been adapted for use on an individual home basis?

Photovoltaic

Which of the following is not seen as an advantage of increasing our use of solar energy?

Production and storage of solar energy is cost-efficient compared to fossil fuels

Alternative energy sources are currently being researched in effort to replace our dependence on fossil fuels. Which is not a current research effort in this regard?

Reintroducing the use of tetraethyl lead to increase the octane rating of gasoline *Remember that lead causes brain damage.

Argon, which comprises almost 1 percent of the atmosphere, is approximately 27 times more abundant than CO2, but does not contribute to global warming. Which explanation accounts for this fact?

Single atoms do not have bonds, therefore do not vibrate *Remember that it is vibration of bonds that causes warming.

The O2 molecule breaks apart at lower wavelengths than the O3 molecule. What is the main reason for this? (Hint: Draw the Lewis structures.)

The average bond in O2 is shorter and stronger than that of O3 *Remember that multiple bonds are shorter and stronger than their single counterparts.

Which is a known risk associated with nuclear power plants?

The cooling water source can suffer thermal pollution *This is assuming that there is no accident, meltdown, etc.

The ability of a molecule to absorb infrared radiation is measured with IR spectrometers, which report the frequency of light absorbed in units of cm¯1. Which explanation best describes this unit?

The number of wavelengths in 1 cm for a specific frequency of light *Remember that this would tell the amount of light "per centimeter."

What two factors are considered when determining the risk assessment for air pollutants?

Toxicity and exposure *remember that some things are poisonous in the short time frame and others are toxic after long time frames.

Which region of the ultraviolet spectrum is absorbed least by the atmosphere?

UV-A *the more energetic wavelengths are absorbed by oxygen gas and ozone molecules

Which statement is correct?

UV-C is the most energetic of the three forms of UV light *remember that UV-A has the longest wavelength while UV-C has the shortest wavelength

Increasing wavelength of light goes in this order.

Ultraviolet -> visible -> infrared

Which color of visible light has the shortest wavelength?

Violet

Which compounds are used in mineral-based sunscreens?

ZnO and TiO2

Which of the following molecules are polar? a) H2S b) CO2 c) BCl3 d) H2O

a, d

The energy needed to initiate a chemical reaction is called the

activation energy.

The "doping" of a semiconductor to improve its performance means

adding small amounts of other elements to the pure semiconductor to change the freedom of electron motion throughout the crystal. *This is necessary to allow electrons to flow.

The structure of ozone most closely resembles a

bent molecule with the same length of chemical bonds, for example,

The general term for plant matter such as trees, grasses, agricultural crops, or other biological material is

biomass

Light behaves like

both a particle and a wave.

The name of the compound formed by combining one carbon atom with two oxygen atoms to form is

carbon dioxide.

Given this diagram, this semiconductor is

carrying an extra electron *Notice the electron environment around the doped atom.

A substance that can be broken down into two or more simpler substances by chemical methods is called a(n)

compound

What is the greatest source of indoor air pollution in developing countries?

cookstoves

A recent set of advertisements has a picture of an aluminum can with an aluminum-frame bicycle, along with a hypothetical quote from the can that reads: "I want to be a bike. Recycle me." The analysis of the life cycle of an item starting with its raw materials and ending with the used item becoming the raw material for new products is called

cradle-to-cradle.

Rank the following solutions in order of increasing concentration: a) 32.3 g of NaCl in 100 mL of water b) 0.10 mol of NaCl in 10 mL of water c) 62.1 g of NaCl in 1 L of water d) 0.25 M NaCl solution

d < c < a < b

P2O5 is the chemical formula for

diphosphorus pentoxide.

The process by which a solution is heated to its boiling point and the vapors are condensed and collected is known as

distillation *This is a method of purifying substances that is used widely in industry.

What term is defined as the flow of electrons from one location to another?

electricity

Oxidation and reduction of atoms involves a change in the number of ________ in the atom.

electrons

Radiative forcings are

factors that influence the balance of Earth's incoming and outgoing radiation. *Remember that forcings can be positive or negative.

Radiative forcings are

factors that influence the balance of Earth's incoming and outgoing radiation. *remember that forcings can be positive or negative

The more toxic the pollutant, the higher the concentration is set when concerning air quality standards.

false

To date, solar radiation is not a practical source for the production of electricity used to power

fleets of taxis. *Solar cells must be stationary and have batteries to store energy for times that the sky is not sunny.

A gasoline's octane rating is a measure of the

gasoline's resistance to causing knocking in a vehicle's engine.

On a Periodic Table, the columns of elements with similar properties are

groups *the horizontal rows are the periods

Cracking is

the breaking of larger molecules into smaller ones. *This is just what it sounds like, just like cracking an egg.

Semiconductors are more effective than metals as converters of solar radiation into electricity because

the energy contained in sunlight gives the valence electrons in the semiconductor atoms the extra energy they need to "flow" throughout the solid. *Semiconductors are made to interact with the wavelengths of light in sunlight while metals are not.

Which symbol(s) represent(s) elements in the noble gas family?

the red column

The main reason that water supplies are chlorinated is

to kill disease-causing organisms in the water.

Ozone is considered an air pollutant in the ________ but is a valuable protective layer in the ________.

troposphere; stratosphere *remember that we live in the troposphere

Even though the concentration of air pollution has gone down over time, people in some metropolitan areas still breath are that contains unhealthy levels of pollutants.

true

Soft lignite (brown coal) is the lowest grade of coal. Since it has undergone the least change since burial, its chemical composition—and hence its heat of combustion—is most similar to that of

wood

Which is a correct statement of the second law of thermodynamics?

Entropy of the universe is constantly increasing

The property of matter that determines the direction of heat flow is the

temperature

Which best symbolizes the hydrogen bonding between two water molecules?

*Remember that the hydrogen bond is between H and a F, O, or N on another molecule.

What type of radiation is given off in this nuclear reaction?

Beta *mass #: no change Atomic #: increased by 1

Which of these statements about biodiesel is not true?

Biodiesel has been withdrawn from several states due to health concerns

Which of these colors in the rainbow has the shortest wavelength?

Blue *Remember ROY G. BIV to help with the colors from red (longest wavelength) to violet (shortest wavelength).

Scientists have correlated average global temperature with atmospheric carbon dioxide levels for the last 160,000 years using ice cores from Antarctica. How is the carbon dioxide level determined?

By measuring the CO2 concentration in trapped air bubbles in the ice layers *Remember that atmospheric gases are trapped in the ice layers.

Which one of the following hydrocarbons would have the highest boiling point?

C

Which reaction accounts for the fact that the pH of rain is naturally slightly acidic?

CO2 + H2O → H+ + HCO3¯

Although carbon dioxide is the primary compound discussed with respect to global warming; of the common atmospheric components the global warming potential (GWP) of a carbon dioxide molecule is very low. Which statement best explains this pair of facts?

CO2 exists in relatively high concentrations *Remember that it is both concentration and GWP which determine what level of warming might come from any one gas.

What is the chemical formula for carbon disulfide?

CS2

What is the role of polar stratospheric clouds (PSCs) on the destruction of ozone?

Chemical reactions occur on the clouds that convert molecules that do no damage to those that deplete ozone. *remember that PSCs only form in the antarctic and that is where the ozone hole exists.

Which form of water disinfection continues to provide antibacterial protection after the water leaves the purification plant?

Chlorination

Which contributes to the ozone hole?

Chlorofluorocarbons (CFCs) *Only CFCs contain chlorine, which acts as a catalyst for ozone destruction. The others are environmental concerns, but don't contribute to the ozone hole.

Which is not a form of chlorine used to disinfect water?

Chloroform

Which is an advantage of using coal over petroleum as a source of energy in the United States?

Coal reserves in the United States are far greater than petroleum reserves

Which corresponds to the composition of the ion typically formed by magnesium?

D

In the famous equation E = mc2, the symbols represent

E = energy, m = mass, c = speed of light.

Which characteristics pertain to the problem of global warming? i. Possible consequences include altered climate and increased sea level. ii. Heat energy radiated by the earth is captured by atmospheric molecules. iii. Increased skin cancer incidence and damage to radiation sensitive species has been observed. iv. The concentration of stratospheric ozone is declining.

i and ii only *Remember that global warming is leading to climate change but has nothing to do with UV radiation or ozone.

Which practices might be described as carbon sequestration?i. Planting treesii. Deforestationiii. Pumping carbon dioxide deep into the oceaniv. Increasing combustion of fossil fuels

i and iii only *Remember that sequestration means trapping the CO2 where it cannot enter the atmosphere.

Methane is approximately 23 times more powerful than carbon dioxide as a greenhouse gas. Which are significant sources of methane emissions? i. The digestive systems of ruminants (cows, sheep, etc.) ii. Automobile exhaust iii. Rice cultivation iv. Decaying wetland vegetation

i, iii, and iv only

Which occurrences or processes are expected to reduce the level of atmospheric carbon? i. Decaying plant and animal remains ii. The growth of trees iii. Formation of carbonate rock in the ocean iv. Animal respiration

ii and iii only *Remember that plants take in CO2 while animals exhale CO2.

Which is not true of radioactive half-life? Radioactive half-life is

increased by heating the isotope. *Remember that half-life is a characteristic of the substance and nothing else.

Chlorofluorocarbons rise to the stratosphere and

interact with UV energy to produce free radicals that destroy ozone.

The speed of light in air

is independent of the wavelength and frequency of light. *Remember that light can travel in vacuum and is a constant.

Land use changes have a big impact on global warming because of their effect on albedo. Albedo

is the ratio of electromagnetic radiation reflected by a surface to the amount of radiation hitting that surface. *Remember that is very influential when examining how much heat the earth absorbs.

Compounds with the same chemical formulas but different molecular structures are called

isomers

Which of the following is a proper use for a calorimeter?

measuring heat of combustion *Remember that these work to find temperature change that occurs due to a chemical reaction.

The most numerous of the elements are the

metals

Air is a(n)

mixture *there are several substances in air

Which is a fossil fuel?

natual gas *Remember that fossil fuels are formed of plants and animals that lived millions of years ago and now are transformed.

Ozone is a secondary pollutant. A secondary pollutant is

not produced directly but as the product of the interaction of two or more pollutants. *this has nothing to do with safety

The atomic number is the

number of protons in the nucleus *the protons define the element

Sunlight (solar radiation) may be turned directly into electricity using ________ cells.

photovoltaic

The Industrial Revolution is a key point in the Earth's atmospheric history because

prior to that time large deposits of petroleum and coal were not being used as energy sources. *Remember that it is combustion of fossil fuels that facilitated the Industrial Revolution.

Which one of the following is a subatomic particle located in the center of the atom and has a positive charge?

protons

Which compound should be the most soluble in water?

refer to image

The fact that carbon (C) is less electronegative than nitrogen (N) means that in a C — N bond, the

shared electrons are closer to the N atom than to the C atom. *Remember that electronegativity is a measure of how much an atom attracts electrons in a covalent bond.