Pcsst Chemistry Final review Conceptual

What prompted early scientists to propose that the ray of the cathode ray tube was actually a negatively charged particle?

(note that opposite charges are attracted to each other) The correct answer is: The ray was attracted to positively charged electric plates..

If the following generic atom were to undergo ionization, what would be the charge of the most likely product? •X•

+2

Which has the greatest number of molecules? a. 28 g of nitrogen, N2 b. 32 g of oxygen, O2 c. 32 g of methane, CH4 d. 38 g of fluorine, F2

-for each choice except CH4, the number corresponds to the substance's formula mass; thus each mass (in grams) represents one mole (i.e., Avogadro's number) of molecules. Since the formula mass of CH4 is 16, then 32 grams of CH4 would have twice as many (two moles) molecules. The correct answer is: 32 g of methane, CH4.

Which has stronger attractions among its submicroscopic particles: a solid at 25°C or a gas at 25°C?

-particles in a solid have much stronger attractions to each other than do particles in a gas The correct answer is: The attractions among the submicroscopic particles of the solid must be stronger than the attractions among the particles of the gas

Why are exothermic reactions often self-sustaining?

.5--exothermic implies that energy is released; when energy spreads out, entropy is increased The correct answer is: They spread energy out to the surroundings, increasing entropy..

Which of the above reactions would proceed the fastest?

.6--Higher concentrations of reactants lead to more frequent collisions, which in turn leads to a faster reaction rate. The correct answer is: c.

According to the following reaction, which molecule is acting as an acid? H2O + NH3 -> OH- + NH4+

0.1--an acid is a substance that donates H+ (a proton) to another substance The correct answer is: H2O.

Which of the following would cause the worst burn? a. 1 gram of steam at 100°C b. 1 gram of water at 100°C c. 1 gram of water at 50°C d. 1 gram of water at 0°C e. 1 gram of ice at 0°C

1 gram of steam at 100°C.

What is a base according to the Bronsted-Lowry definition?

10.1 a base is a substance that accepts H+ (a proton) from another substance The correct answer is: anything that accepts a hydrogen ion.

For the following reaction, identify whether the compound in *bold is behaving as an acid or a base. H3PO4 + H2O = *H2PO4- + H30+

10.1--Each side of a reversible acid-base reaction (indicated by the double arrow) has one acid and one base. Whichever direction the reaction is viewed (left to right, or right to left), the acid is the substance that donates the H+ (a proton), while the base is the one that accepts it. The correct answer is: base.

According to the following reaction, which molecule is acting as a base? OH- + NH4+ -> H2O + NH3

10.1--a base is a substance that accepts H+ (a proton) from another substance The correct answer is: OH-.

Put the following aqueous solutions in order from least to greatest electrical conductivity: A. 0.001M HCl (hydrochloric acid) B. 10M HCl (hydrochloric acid) C. 0.001M C2H4O2 (acetic acid) D. 10M C2H4O2 (acetic acid)

10.2--the more ions in an aqueous solution, the better that solution conducts electricity. For a strong acid such as HCl, nearly all of the molecules donate H+ to make ions. For a weak acid such as acetic acid, only a small percentage (~1%) of the molecules create ions. Note that the concentrated 10M solution of acetic acid has 10,000 times as many molecules as a dilute 0.001M solution of HCl. So, even though only about 1% of the acetic acid molecules create ions, it will still have about 100 times as many ions as the dilute HCl solution. The correct answer is: C < A < D < B

Which of the above images represents a water solution of the strongest acid (HA)? (Note that the water molecules are not shown.)

10.2--the strength of an acid is defined by what percentage of the molecules in aqueous solution donate their hydrogen ions to water and become ions. The correct answer is: C.

What would the concentration of H3O+ be if the concentration of OH- was 1 x 10-11M?

10.3-- [H3O+] x [OH-] = Kw = 1 x 10-14 Note that the exponents always have to add up to -14. The correct answer is: 1 x 10-3.

What happens to the hydroxide ion concentration if you decrease the hydronium ion concentration in an aqueous solution?

10.3--the product of hydroxide ion and hydronium ion concentrations is always a constant, so when one goes up, the other goes down. The correct answer is: Increases.

If some NaOH is added to a pH 8.0 buffer solution, which of the following is the most likely pH that results?

10.4--a buffer solution is one that resists large changes in pH; when a strong base is added to a buffer solution, the pH will increase only slightly The correct answer is: 8.5.

Which of the following contributes to why scientists have a difficult time estimating the future rate and extent of global warming?

10.6--Increased temperatures may lead to mass plant extinctions or to greater plant growth. In turn, plant growth should help remove carbon dioxide from the atmosphere, but it could lead to increased methane production (another potent greenhouse gas). The correct answer is: They are unsure about whether warming will lead to a net absorption or release of greenhouse gases by plants and microbes..

In the greenhouse-effect analogy between the Earth and a car left out in the sun, which part of the Earth is analogous to the car's windows?

10.6--like a car's windows, the atmosphere transmits visible light, but reflects infrared light that is re-radiated from the earth's surface. The correct answer is: the atmosphere.

Compared to microtechnology, nanotechnology focuses on a scale that is about

1000 times smaller..

Upon ingestion, grain alcohol, C2H6O, is metabolized into acetaldehyde, C2H4O, which is a toxic substance causing headaches as well as joint pains typical of a "hangover". Is the grain alcohol oxidized or reduced as it transforms into acetaldehyde?

11.1, end of Ch 11 question #53--Loss of H atoms by a substance corresponds to oxidation. The correct answer is: The grain alcohol is oxidized..

Which of the following species is the reducing agent? 2 Cu + Br2 -> 2 CuBr

11.1--Br2 is reduced to 2 Br- in the ionic compound CuBr. Since Cu caused this reduction, it is the reducing agent. The correct answer is: Cu.

How many electrons are gained or lost in the following half-reaction? 2Na -> 2Na+

11.1--each of the two Na atoms lose one electron to get a +1 charge The correct answer is: 2 electrons are lost.

Which of the following materials is most likely to undergo reduction? a. K b. Fe c. Al d. Cl2 e. FeCl2

11.1--elements toward the bottom left of the periodic table are more likely to be oxidized The correct answer is: Cl2.

Jewelry is often manufactured by electroplating an expensive metal such as gold over a cheaper metal. A setup for this process can be sketched as follows: What would happen if the battery connections were suddenly reversed?

11.6 and 11.8--if the battery terminals were reversed, the gold electrode would become negatively charged, thereby attracting the gold ions from solution and reversing the flow in the figure. The correct answer is: Gold ions in solution would begin to electroplate onto the gold electrode..

What would the formula be for the following stick model? (a 5 sided ring with 1 stick coming off)

12.1--remember that each line represents a single bond between carbon atoms in the molecule. This molecule will have 6 carbon atoms--5 in the ring, plus one more at the end of the side branch. The correct answer is: C6H12.

Which of the following is a saturated molecule?

12.2--a saturated hydrocarbon has only single bonds (no double or triple bonds) to other carbons, and hence is "saturated" with hydrogen atoms. The correct answer is: None of these .

Which of the above molecules would be acidic?

12.5 and 12.6--carboxylic acid compounds (d) are of course acidic; phenol compounds (a) are slightly acidic as well. The correct answer is: a or d .

Soft-drink makers often react caffeine with phosphoric acid to produce the salt form of caffeine shown below. Why?

12.5--amines are basic, and therefore accept hydrogen ions from acids to become ionized (i.e., to form a salt). Ions are of course very soluble in water. The correct answer is: The salt form of caffeine dissolves well in cold water..

Which of the above molecules would you use to make an ester?

12.6--An ester can be made by reacting an alcohol (a) with a carboxylic acid (d). Note that salicylic acid has both groups, and can thus play either role when making an ester (e.g., compare aspirin to methyl salicylate). The correct answer is: a or d .

Which of the following monomers could be used to make a condensation polymer? a. H2C=CH-CH3 b. CH3CH2CH3 c. HOCH2CH2OH

12.8--a condensation polymer requires a monomer that has two functional groups on the same molecule. The correct answer is: HOCH2CH2OH.

Which of the following monomers could be used to make an addition polymer? H2C=CH-CH3 b. CH3CH2CH3 c. HOCH2CH2OH

12.8--an addition polymer requires a monomer that contains a double or triple bond. This particular monomer would be used to create polypropylene (PP). The correct answer is: H2C=CH-CH3.

Which of the following reaction energies is the least endothermic (but still an endothermic reaction)? a. 540 kJ/mole b. -540 kJ/mole c. 125 kj/mole d. -125 kJ/mole

125 kj/mole.

If a neutral element has 8 neutrons and 7 electrons, which expression correctly identifies the element?

15 N 7 if neutral charge, protons = electrons (=7), so must be N. Then, 8 neutrons implies the isotope is N-15 (=7p+8n).

Given that the bond energy of N2 is 946 kJ/mole, the bond energy of O2 is 498 kJ/mole and the NO bond energy is 631 kJ/mole, how much energy is required for one mole of the following reaction? N2 + O2 -> 2 NO

182 kJ N-N (+946) O-O (+498) = +1444 NO (-631) NO (-631) = -1262 +182

Which of the above stick structures would have the lowest octane rating for use in your engine?

2.1--the less branched the hydrocarbon, the lower the octane rating (and the more likely to cause engine knocking) The correct answer is: a.

How many valence electrons does gallium (Ga, atomic no. = 31) have?

3

How many moles of H-O bonds are formed if you react hydrogen with oxygen according to the following reaction? 2 H2 + O2 -> 2 H2O

4

If you have two molecules of TiO2, how many oxygen atoms would you have?

4

Which of the following provides the minimum amount of protection you need to block the following form of radiation? Gamma

5.1--alpha can be blocked by paper or regular clothing, beta by thick or dense materials such as thick leather or sheets of aluminum, and gamma only by very dense materials such as lead. The correct answer is: lead suit.

Complete the following nuclear equation: 210 ...............4 ...PO -> ?? + He 84 ................2

5.4--alpha emission involves ejection of a Helium-4 nucleus (2 protons + 2 neutrons) from the atomic nucleus, so that the atomic number decreases by 2 and the mass number by 4. The correct answer is: B. 206 Pb 82

If carbon-14 is a beta emitter, what is the likely product of radioactive decay? a. nitrogen-14 b. carbon-12 c. oxygen-18 d. berrylium-10

5.4--beta emission involves a neutron decaying into a proton (which stays in the nucleus) and an electron (which is emitted). Because a neutron transforms into a proton, the atomic number increases by one (C to N), but the mass number stays the same (14). The correct answer is: nitrogen-14.

Which of the following nuclear equations correctly describes beta emission?

5.4--beta emission invovls a neutron decaing into a proton (which stays in the nucleus) and an electron (which is emitted). Because a neutron transforms into a proton, the atomic number increases by one, but the mass number stays the same.

Which type of radiation alpha, beta, or gamma results in the least change in atomic number?

5.4--both alpha and beta radiation involve a change in atomic number (number of protons), but gamma radiation does not (just energy). The correct answer is: gamma radiation.

If a material has a half-life of 24 hours, how long do you have to wait until the amount of radioisotope is 1/4 its original amount?

5.5--In 24 hrs (one half-life) there will be 1/2 the original amont. After another 24 hrs, there will be 1/2 of 1/2, or 1/4, the original amount. The correct answer is: 48 hours.

Which of the following statements about carbon-14 dating is true?

5.6--Carbon-14 dating can closely estimate (with about 15% uncertainty) the age of any once-living object that died less than 50,000 years ago. The correct answer is: None of these .

Which of the following statements about chain reactions is true?

5.7--A critical mass is the minimum amount of material needed for a sustainable chain reaction. The correct answer is: A sustainable chain reaction will only take place when a critical mass of material has been assembled. .

About how many molecules of sucrose are in 1 L of a 1 M solution of sucrose?

6 x 10 (to the 23rd power) molecules of sucrose

Hydrogen selenide is a covalent compound of selenium, Se, and hydrogen, H. What is its chemical formula (Hint: draw the Lewis Dot structure)?

6.5, and Lewis Dot Tutorial in Ch 6 Concept Review--note also that because Se and O are in the same column of the periodic table, they bond in similar ways (H2Se and H2O have similar formulas, bonding, and molecular shapes). The correct answer is: H2Se.

Which of the following molecules should have the same molecular shape and approximate bond angles as water, H2O?

6.6 and Molecular Polarity tutorial in Ch 6 Concept Review--note that all elements in same group have same Lewis dot structure, and thus give same shape (all other things equal) The correct answer is: H2S.

Which of the following intermolecular forces are most relevant to why nonpolar molecules like gasoline (C8H18) have only limited solubility in water?

7.1 and 7.4--mixing molecules requires consideration of 3 types of interactions: 1. solute-solute, 2. solvent-solvent, and 3. solute-solvent. When all are comparable, the substances mix well. Here, they are of 3 different types (1. induced dipole-induced dipole, 2. hydrogen bonding, 3. dipole-induced dipole). The correct answer is: several of these.

Which of the following molecules would you expect to be the least attracted to a Na+ ion? a. H-F b. H-H c. H-Cl d. F- e. HO-

7.1--An ion is most attracted to an oppositely charged ion, next strongly to a polar molecule, and least strongly to a nonpolar molecule. In this case, H-H is the only nonpolar molecule. The correct answer is: H-H.

Which of the following would have the highest boiling point? a. CH4 b. C3H8 c. C5H12 d. C8H18

7.1--for nonpolar molecules, the induced dipole attractions increase in strength as the molecules get larger ('the Velcro concept'). The correct answer is: C8H18.

Which of the following solutions is the most concentrated? a. 0.5 L of a 3 M solution b. 3.0 L of a 0.5 M solution c. 2.0 L of a 1 M solution d. 0.5 L of a 1 M solution e. 2.0 L of a 2 M solution

7.3--molarity (M) is a measure of how concentrated a solution is; 3 M is the highest of these choices. The correct answer is: 0.5 L of a 3 M solution.

Scuba divers are at risk of getting a potentially fatal injury known as the bends. This occurs if they ascend too rapidly after spending a long time deep underwater (where pressure is greater) breathing compressed air. Based on your understanding of the solubility of gases, choose a reasonable explanation for why this might be dangerous.

7.4--this is similar to what happens when you open a carbonated beverage. The correct answer is: Dissolved nitrogen becomes less soluble as pressure decreases, and bubbles out of the blood..

Which of the above (a,b,c,d) might best describe how soap behaves in a nonpolar solvent like turpentine?

7.5--the nonpolar portions would be attracted to the nonpolar solvent molecules, while the polar groups would cluster together away from the solvent. The correct answer is: c.

Why do red blood cells, which contain an aqueous solution of dissolved ions and minerals, burst when placed in fresh water?

7.7, Ch 7 RAT #9--the cell membrane acts like a semi-permeable membrane; the dissolved ions inside the cell cause water to move into the cell through osmosis, eventually bursting the cells open. The correct answer is: More water molecules enter the cell than leave the cell..

If you insulate a mixture of water and ice at 0°C what will happen?

8.2--a mixture of water and ice can co-exist at a temperature of 0 deg C (at normal pressures), since the rate at which molecules go from liquid to solid is exactly balanced by the rate they go from solid to liquid. If you were to add heat, you would increase the rate of melting relative to freezing, and the ice would eventually melt; if you were to remove heat, the opposite would happen. The correct answer is: The overall proportions of water and ice will remain constant..

When a plant grows, where does most of the increased mass of the plant come from?

9.1, 9.5 and 2.2--atoms are conserved in all chemical processes. Most of a plant's mass is made up of C, H, and O-containing carbohydrate molecules, which are created through the process of photosynthesis. In this process, carbon dioxide from the air and water (from the air and roots) are chemically reacted to make carbohydrate molecules that provide the plant's structure, and oxygen that is released to the atmosphere. Since this reaction is endothermic (energy-absorbing), it must be driven by an outside energy source (sunlight). The correct answer is: the air.

A 100-gram sample of which of the following will contain the fewest atoms?

9.2--just as 10 pounds of golf balls will contain fewer balls than 10 pounds of ping-pong balls, the heaviest element will contain the fewest number of atoms in an equivalent mass sample. The correct answer is: Fe .

For the above energy profiles, which reaction would proceed the slowest? d. starts low rizes sharply, goes down a wee bit, then level out.

9.6--d has the highest activation energy, corresponding to the 'height of the hill' as compared to the reactant energy The correct answer is: d.

How might the spectrum of an atom appear if its electrons were not restricted to particular energy levels?

A broad spectrum of all colors would be observed..

Which of the following statements best describes a critical mass?

A critical mass is the minimum amount of material that will sustain a chain reaction.

Describe how a boiling liquid can be used to cool something (i.e., a refrigerator).

A low boiling liquid absorbs heat energy, dropping the temperature..

Distinguish between a scientific hypothesis and a theory.

A scientific hypothesis is a testable assumption, while a theory is a well-verified idea used to explain a broad range of phenomena.

What do the components of a conceptual model have in common?

All components interact with each other.

Which of the following statements about carbon dioxide are true?

All: a. Human activities emit more carbon dioxide than any other gas. b. Atmospheric carbon dioxide concentration has increased since the Industrial Revolution. c. Carbon dioxide is being released at a faster rate than it is being absorbed. d. Carbon dioxide is not the most abundant greenhouse gas.

A potential application of hydrogen sulfide induced suspended animation is

All: a. the protection of transplant organs prior to the transplant surgery. b. slowing down the bodily damage caused by heart attacks and strokes. c. long distant manned space voyages.

Why is reproducibility such a vital component of science?

An experiment can only be considered valid if other scientists can reproduce the results.

How might the demand for reproducibility in science have the long-run effect of compelling honesty?

Any false claims are eventually uncovered. Scientists, therefore, stand to gain most from reporting their results truthfully. b. A scientist who has knowingly falsifies any bit of evidence runs the risk of losing credibility for all his or her life's work. c. Science is about discovering the rules of nature. A scientist who creates his or her own rules through dishonesty, which may not be reproducible in other laboratories, is not truly doing science.

Why does a lake freeze from the top down?

As near-freezing water cools further, it gets less dense and floats..

As an ice cube floating in a glass of water melts, what happens to the water level?

As the ice melts, the water level does not change--the melting ice "caves in" and exactly fills the open spaces..

If you remove two protons and two neutrons from a gold atom (Au), what new element is formed?

Au has 79 protons; 2 less would be 77, which is Ir (number of neutrons does not affect which element). The correct answer is: Ir.

Account for the observation that ethyl alcohol, C2H5OH, dissolves readily in water but dimethyl ether, CH3OCH3, which has the same number and kinds of atoms, does not.

Because dimethyl ether lacks an -OH group, it is less polar than is ethyl alcohol and is not as soluble in water

Which color of light comes from the higher energy transition, red or blue?

Blue is a higher frequency and therefore corresponds to a higher energy level transition.

How are the disinfecting properties of chlorine and ozone similar to each other?

Both are effective at destroying bacteria..

Which of the following molecules would probably be isolated closest to the top of a fractionating tower at a refinery? a. C4H10 b. C8H18 c. C10H22 d. C20H42 e. C40H82

C4H10.

Which of the following compounds is found in alcoholic beverages? a. CH3CH2OH b. CH3CH2CH3 c. CH3OH d. CH3CH=CH2 e. CH4

CH3CH2OH

Which of the following compounds is likely to have the best water solubility? a. CH3CH2OH b. CH3CH2CH2CH2OH c. CH3CH2CH2CH2CH2CH2OH d. CH3CH2CH2CH2CH2CH2CH2CH2OH

CH3CH2OH

Which of the following substances contains F- ions?

CaF2.

What would be the best explanation for the fact that most natural water has a pH of about 5.6?

Carbon dioxide reacts with water to form an acid..

Given that the total number of atoms on our planet remains fairly constant, how is it possible for a nation to deplete a natural resource such as a metal?

Concentrated sources of metal atoms are used up, leaving dispersed sources that are not economically viable.

How do the electron-dot structures of elements in the same group in the periodic table compare with one another?

Elements of the same group have the same number of valence electrons.

Which of the following is most likely to have the weakest induced dipole-induced dipole interaction? a. Cl2 b. Br2 c. F2 d. I2

F2

How is a fuel cell different from a battery?

Fuel cells will run continuously as long as fuel is supplied..

Which of the following statements about fusion is true? Select one: a. Fusion is easier than fission. b. Fusion reactions have no critical-mass requirement. c. Fusion reactions can be easily controlled to make energy. d. Fusion produces no harmful radiation. e. None of these

Fusion reactions have no critical-mass requirement..

Which of the following is a mixture? a. oxygen b. nitrogen c. water d. granite rock e. copper

Granite is a mixture of several different compounds. All of the other choices are pure substances (elements or compounds). The correct answer is: granite rock.

Which of the following compounds has polar covalent bonds?. H2O b. BaF2 c. S8 d. Ne e. CH4

H2O

Which of the following is not a chemical change?

In this case, a large object is simply broken into smaller pieces. There is no rearrangement at the atomic level to form a new substance. The correct answer is: a rock being crushed to powder.

How many grams of water can be formed from the reaction of 16 grams of oxygen with 4 grams of hydrogen?

In this case, all 16g of the oxygen will be used up, along with 2g of the hydrogen, to make 18g of water; 2g of hydrogen will remain unreacted since there is insufficient oxygen available. The correct answer is: 18.

Which of the following statements best describe water, but not most other substances?

Increases in density as it melts..

Which of the following statements accurately describes the action of ozone?

It absorbs UV radiation and converts it to heat..

Why does soap decrease the surface tension of water?

It disrupts hydrogen bonding among water molecules at the surface..

Where does most of the solid mass of raw sewage end up after being collected at a treatment facility?

It is buried in landfills..

What is the valence shell?

It is the outermost shell of electrons in an atom..

How does a catalyst increase the rate of a reaction?

It lowers the activation energy..

In the reaction below, what does the = symbol mean? (its actually a double arrow sign with and arrow going both ways) OH- + NH4+ = H2O + NH3

It means that the forward and backward reactions are happening at the same time..

Which of the following statements does not describe a proton?

It orbits around the nucleus of an atom.

Which of the following experiments helped to determine the ratio of the charge of an electron to its mass?

J.J. Thompson's cathode ray deflection experiments.

Which of the following metals would be the hardest to reduce to its native form from an ore? a. Cu b. Ni c. Fe d. Ti e. K

K

You take 50 mL of small BB's and combine them with 50 mL of large BB's and you get a total of 90 mL of BB's of mixed size. Which of the following statements best explains this?

Many of the smaller BB's are able to fit within the pockets of space that were empty within the number of large BB's.

Mercury forms a convex meniscus with glass and not the concave meniscus formed by water. What does this tell you about the cohesive forces within mercury versus the adhesive forces between mercury and glass?

Mercury sticks to itself (cohesive forces) better than it sticks to the glass (adhesive forces)..

What property of metal atoms account for many of the observed bulk phenomena seen in metal samples?

Metal atoms easily lose one or more outer electrons..

Which of the following elements will most likely form an ion with a +2 charge? a. Na b. Mg c. Ne d. Si e. Cl

Mg

Which element has the atomic number 12?

Mg.

Magnesium ions carry a 2+ charge, and chloride ions carry a 1- charge. What is the chemical formula for the ionic compound magnesium chloride?

MgCl2

Why does water have a high specific heat?

Much of the added energy is required to break hydrogen bonds..

List the following bonds in order of increasing polarity:

N-N < N-O < N-F < H-F.

For the following balanced reaction, which of the following is a solid?

NaCl . - because it has a (s) next to it.

Oxygen atoms are used to make water molecules. Does this mean that oxygen, O2, and water, H2O, have similar properties?

No, compounds are uniquely different from the elements from which they're made

Which of the following boxes represents a compound?

Note that A shows a mixture of elements, while B shows a pure element. The correct answer is: only C.

What is the name of the following compound? SF3

Note that for a compound made up of 2 nonmetal elements, follow Guideline 2. The correct answer is: sulfur trifluoride.

What is the name of the following compound? CaCl2

Note that for a compound made up of a metal and a nonmetal, follow Guideline 1. The correct answer is: calcium chloride

Which of the following is a heteroatom? a. O b. C c. H d. O and C

O

In a hydrogen fuel cell,

O2 is reduced at the cathode

Ozone is a molecule made up of atoms of the element _______.

Ozone has the chemical formula O3 - Oxygen

Why is a phenol more acidic than a regular alcohol?

Phenols have the ability to spread out the negative charge that forms..

Phosphate ions, PO43-, were once added to detergents to assist in cleaning. What function did they serve?

Phosphate ions would bind to and remove calcium ions, thus acting as a water softening agent..

Which contributes more to an atom's mass: electrons or protons? Which contributes more to an atom's size?

Protons contribute more to an atom's mass while electrons contribute more to its size.

Given that the above energy profiles have the same scale, which of the reactions is the most exothermic?

R starts in middle of scale goes up a wee bit, then drops long way to the bottom and levels out P.

Radium-226 is a common isotope on Earth, but has a half-life of about 1600 years. Given that Earth is some 5 billions years old, why is there any radium at all?

Radium-226 is a "daughter" isotope and the result of the radioactive decay of uranium

An electron in the outermost shell of which group 1 element experiences the greatest effective nuclear charge?a. Sodium, Na b. Potassium, K c. Rubidium, Rb

Sodium, Na. the one with the fewest electrons.

Which of the following polymers might be given credit for ending World War II?

TEFLON

Aluminum metal undergoes the same basic corrosion process that iron does yet it does not decompose as rapidly. Why?

The aluminum oxide acts as a protective layer for the underlying metal..

In which are the molecules moving faster: a swimming pool of boiling water or a cup of boiling water?

The average motion of the molecules in each is the same.

A chemical equation for the combustion of propane, C3H8, is shown below. Through this reaction is the carbon oxidized or reduced? C3H8 + 5O2 -> 3CO2 + 4H2O

The carbon is oxidized.

Why does evaporation cool a liquid?

The departing high-speed molecule takes some kinetic energy with it as it leaves the liquid surface.

Where does the earth receive most of its energy?

The earth receives most of its energy from the Sun, which generates the energy from nuclear fusion reactions. A smaller amount is generated by fission reactions occurring within the core of the earth. The correct answer is: external fusion.

If you add heat energy to water molecules in the form of ice, where does the energy go?

The energy is used to break hydrogen bonds..

Water coming out of volcanic sea vents at the bottom of the ocean can reach temperatures in excess of 300°C without boiling. How is this possible?

The extreme pressure exerted by the miles of ocean water above prevent the formation of any bubbles of water vapor. .

Which of the following statements best describes the strong nuclear force?

The force is very strong but has a very short range..

How do fission power plants work?

The heat from a nuclear reaction is used to boil water..

What chemical change occurs when a wax candle burns?

The heated wax molecules combine with oxygen molecules. .

Does a 2 kg solid iron brick have twice as much mass as a 1 kg solid block of wood? Twice as much volume?

The iron brick has twice the mass, but its volume compared to the block of wood depends on the density of the wood..

The following set of redox reactions takes place when iron is dipped into a solution of copper ions. Fe -> Fe+2 + 2e- Cu+2 + 2e- -> Cu If you had two containers filled with the ion solutions described above with a wire connecting a piece of iron (in container A) and a piece of copper (in container B) and a salt-bridge connecting the two containers, describe what happens.

The iron is transformed into iron ions and the copper ions are transformed into copper metal..

Lakes lying in granite basins, such as those in the northeastern U.S., tend to become acidified by acid rain more readily than lakes lying in limestone basins, such as those found in the midwestern U.S. Why is this so?

The limestone, which is calcium carbonate, serves to neutralize the acid in the rain..

Why does liquid water expand slightly when it is cooled at near-freezing temperatures?

The molecular vibrations slow and the molecules move farther apart due to directional hydrogen bonds..

Which of the following describes what happens when you increase the temperature of a typical substance?

The molecules vibrate faster and move farther apart..

Why might the following nuclear reaction not be very good for energy production in a fusion reactor?

The reactants are too stable and it would cost energy to produce the product due to strong nuclear force..

Imagine that you can see individual molecules. You watch a small collection of molecules that are moving around slowly while vibrating and bumping against each other. The slower moving molecules then start to line up. Soon all the molecules are aligned and vibrating about fixed positions. What is happening?

The sample is being cooled and the material is freezing.

What is the purpose of adding aluminum salts and a base to water during water treatment?

The two together gel and trap dirt and bacteria..

Suppose that water is used in a thermometer instead of mercury. If the temperature is at 4°C and then changes, why can't the thermometer indicate whether the temperature is rising or falling?

The water at 4°C would expand whether the water was cooled or heated..

Why does water expand when it goes from a liquid to a solid?

The water molecules become aligned in a way that creates extra volume..

What do the electron configurations for all the group 18 noble gases have in common?

Their outermost occupied shells are filled to capacity..

How does n-type silicon differ from pure silicon?

There are other elements with more valence electrons than silicon in the silicon matrix..

Would you expect to find more dissolved oxygen in polar or tropical ocean waters? Why?

There would be more dissolved oxygen in the polar oceans because the solubility of oxygen in water increases with decreasing temperature

Why is it so easy for a magnesium atom to lose two electrons?

These two electrons are well shielded from the nuclear charge..

Why aren't solar stills used in more large urban areas?

They take up too much space..

What property of a car's windows cause its interior to heat up when the car is left in the sun?

They transmit visible light but reflect infrared radiation..

Given the following generic chemical reaction, which is the product? X -> Y

Y is the product.

Why might increasing the concentration of a set of reactants increase the rate of reaction?

You have increased the chances that any two reactant molecules will collide and react..

Which of the following statements best describes an element?

a material consisting of only one type of atom

What is an organic compound?

a molecule that is made mostly of carbon with no metals in it.

The following statement describes which subatomic particle best? It does not have an electrical charge.

a neutron.

What does the following element description actually mean? 238 U 92

a uranium atom with 92 protons and 146 neutrons.

Which of the following is the least amount of energy?

a. 1.0 joules b. 1.0 kilojoule c. 1.0 Calorie d. 1.0 kilocalorie e. 1.0 calorie 2.5--note that 1 Calorie = 1 kilocalorie = 1000 calories, and that a joule is about one-fourth of a calorie. The correct answer is: 1.0 joules.

Which temperature is the highest?

a. 100°C b. 100 K c. 100°F The correct answer is: 100°C.

What happens to the freezing temperature of a salt water solution as it becomes more concentrated?

a. As salt water becomes more concentrated, the temperature at which it freezes becomes lower because liquid water molecules are hindered from joining the ice.

Which of the following statements regarding a nucleon is true?

a. Attraction between nucleons changes their mass. b. The mass of a nucleon depends on which nucleus it is in. c. Some of the mass of a nucleon can be converted into energy by breaking certain nuclei. d. a and b e. All of these******

Which of the following best describes a gas?

a. The molecules are moving quickly and are widely spaced.

Which of the following might best explain the reason why electrons are restricted to certain energy levels in an atom?

a. They behave like standing waves that are self-reinforcing.

Which of the following solutions is the most basic? a. a solution with a pH = 14 b. a solution with a pH = 10 c. a solution with a pH = 7 d. a solution with a pH = 4 e. a solution with a pH = 1

a. a solution with a pH = 14

Which of the following materials, with the given specific heats, would cool the fastest under similar circumstances?

a. ammonia, 4.70 J/(g°C) b. water, 4.184 J/(g°C) c. aluminum, 0.90 J/(g°C) d. silver, 0.24 J/(g°C) ********

Which of the following would be a negative ion with a single charge?

a. an atom with 11 protons and 12 electrons

Which element would have chemical properties the most similar to chlorine (Cl)?

a. argon (Ar) b. lead (Pb) c. cerium (Cr) d. indium (In) e. lithium (Li) ****

Which of these properties describes a metal?

a. conducts heat very well b. brittle c. fragile d. transparent e. doesn't conduct electricity very well Answer: poor conductor of electricity.

The bucky ball led to the discovery of a whole new class of molecules called fullerenes. Fullerenes are useful in

a. nanotechnology. b. conducting electricity. c. strengthening materials.

A closed film canister with 30 pennies inside has a greater _______ than the same canister with 15 pennies.

a. volume b. mass c. density d. b and c The correct answer is: b and c.

Which of the following can be classified as matter?

a. water b. sand c. perfume d. ice cream e. All of these *

The functional groups in the molecule below have been circled and numbered. Correctly identify the functional group in this organic molecule that is marked as #2.

amide. CH3-N=O (Nitrogen)

Which of the following atoms is the largest? Cs b. Ba c. Al d. N e. He

atoms tend to get larger as you move down and to the left across the Periodic Table The correct answer is: Cs.

When the benefits of a technological innovation are seen to outweigh the risks

b. the technology is accepted and applied.

Which of the following sources of radiation provides most of our yearly exposure?

background radiation.

Why did Rutherford propose a model for the atom with a very small nucleus containing the bulk of the mass and a positive charge?

because a beam of positively charged particles (alpha particles) were partially reflected by a thin gold foil.

Which loses its outermost electrons more easily: bromine, Br, or krypton, Kr?

because of increasing effective nuclear charge, it gets harder to remove an electron as you move across the Periodic Table from left to right The correct answer is: Br.

The image below shows a beam of radiation passing between two electrically charged plates. Which of the beams is due to a high energy electron?

beta particle (which is simply a high energy electron) is negatively charged and is therefore attracted by the positively charged plate (opposites attract), causing its path to bend as it flies past. The correct answer is: a.

Chemistry is the study of ________.

both matter and transformations of matter .

What is "dry ice" made of?

carbon dioxide.

The chlorinated fluorocarbons molecules are acting as a(n) ________ by converting hundreds of thousands of molecules before they are inactivated.

catalyst.

Is the following transformation representative of a physical change or a chemical change? (2 different atoms paired together > 2 identical atoms paired together.

chemical change because the atoms are connected differently.

Which of the following molecules is a straight-chain hydrocarbon?

continuous flow of sticks

Which of the following is the correct electron dot structure for chlorine (atomic no. = 17)?

d. 7 dots. 3 double pairs and one single electron

As the hydroxide ion concentration decreases, the pH ________.

decreases.

Based on experimental evidence, John Dalton postulated that

each element consists of indivisible, minute particles called atoms.

From a chemical standpoint, recharging a battery is the same as

electrolysis.

A misleading "artifact" of an experiment can be the result of

faulty equipment.

Which of the following is something that is best described as having mostly potential energy?

food. section 2.5--food contains mostly potential energy (contained within its chemical bonds); the other choices involve a great deal of motion and hence would be described as having more kinetic energy.

Heat is given off when a substance

freezes..

Which direction do the photo-ejected electrons in a photovoltaic cell travel?

from the n-type, through a wire, to the p-type, and then back across the junction to the n-type silicon.

Rank the following by relative frequency from highest to lowest:

gamma rays, blue light, red light, radio waves

How would you classify the following material? (filtered) swimming pool water? a. homogeneous mixture b. heterogeneous mixture c. a pure element d. a pure compound e. depends on how many children have been in it

homogeneous mixture.

An old remedy for separating a pair of nested drinking glasses stuck together is to run water at one temperature into the inner glass and then run water at a different temperature over the surface of the outer glass. Which water should be hot and which should be cold?

hot water will cause outer glass to expand, while cold water will cause inner glass to contract. The correct answer is: fill the inner glass with cold water while running hot water over the outer glass.

Which of the following is the main form of intermolecular attraction between water molecules?

hydrogen bonding.

A sample of radium is usually a little warmer than its surroundings because

its atoms are continually being struck by alpha and beta particles.

Which of the above has the highest frequency?

least amount of space between the peaks. More peaks per distance.

How would you describe the size of the following object? a blood cell

microscopic

In a solution of 77 percent nitrogen and 23 percent oxygen, which is the solvent?

nitrogen

According to the following balanced chemical equation, if you want to generate 20 molecules of H2O, how many molecules of O2 do you need? 2 H2 + O2 -> 2 H2O

note that coefficients in the reaction equation indicate the lowest whole number ratios in which the substances react. Since 2 water molecules are produced for each oxygen molecule, 20 water molecules will be produced from 10 oxygen molecules. The correct answer is: 10.

What coefficients balance the following equation? _______P4(s) + _______H2(g) -> _______PH3(g)

note that these coefficients indicate the lowest whole number ratios in which the substances react The correct answer is: 1, 6, 4.

The hypothesis that the moon may have resulted from an asteroid collision with Earth was prompted by

noting that the chemical composition of rocks on the moon is very similar to that of Earth.

What is the difference between a dipole-dipole interaction and an ion-dipole interaction?

one involves an attraction between neutral molecules while the other involves an interaction between a neutral molecule and an ion.

The repeating trends that take place when examining the elements are called ________.

periodicity

What is the name for the following polyatomic ion? PO4-3

phosphate.

Dmitri Mendeleev

predicted the existence of elements not yet discovered.

Why do aerosol cans explode if heated?

pressure increases proportionally with (absolute) temperature The correct answer is: An increase in temperature will increase the pressure inside the aerosol can. When the pressure inside the can exceeds the pressure limit of the can, it explodes..

How would you refine a metal from a metal sulfide?

react it with oxygen at high temperature.

In a battery, the following two oxidation-reduction reactions are taking place:Which of the following is true? rxn A: Zn -> Zn+2 + 2e- rxn B: 2NH4+ + 2e- -> 2NH3 + H2

rxn A is oxidation and occurs at the anode.

What physical quantities discussed in this chapter change most when a junked car is neatly crushed into a compact cube?

section 2.4--the mass of an object does not change when it is crushed, but its volume decreases and hence its density increases. The correct answer is: The volume of the car changes as well as its average density..

Which of the following would best describe heat?

section 2.6 The correct answer is: Heat is energy that moves from high to low temperature objects..

Organic synthesis is

the building of organic molecules. .

What is a reduction?

the gain of electrons

Which of the following would not be considered a chemical property?

the temperature at which a liquid will boil b. light sensitivity c. whether a metal will rust or not d. whether a material will dissolve in acid or not e. the tendency of a material to explode 3.1, Boiling, like other changes of state, is a physical change--a new substance is not formed. The correct answer is: the temperature at which a liquid will boil.

Which of the following does not describe volume?

the weight of a given object

Because aspirin is acidic, when someone takes an overdose of aspirin, their blood pH decreases. What is their body's natural physiologic response?

to breathe faster so as to eliminate CO2 and thereby increase pH

Which produces more energy, the fissioning of a single uranium nucleus or the fusing of a pair of deuterium (hydrogen-2) nuclei? Why?

using a pair of deuterium nuclei produces more energy because there is a larger change in the mass per nucleon during the process..

What was the first synthetically enhanced polymeric hydrocarbon extensively utilized for its material properties?

vulcanized-rubber.

What is the gas found within a bubble of boiling water?

water vapor.

Can an object have mass without having weight? Can it have weight without having mass?

yes and no