posted by Winona .
I have a chemistry test that I need help with. My answers have stars by them Can someone please help me with the answers to this test???
Part 1 – Matter as Energy & Structure
1. When a pair of electrons is shared between two atoms, a covalent bond is said to have formed. Most often, the pair is formed
a. by excess valence electrons b. as one atom contributes both electrons* c. as each atom contributes one electron d. as one atom “steals” two electrons from the other
2. A molecule of water is composed of two atoms of hydrogen and one atom of oxygen (H2O). If the atomic mass number of hydrogen is 1 and the molecular mass of water is 18, the atomic mass of oxygen must be
a. 36 b. 16* c. 18 d. 14
3. Physical properties of matter include all of the following except
a. reactivity* b. odor c. density d. solubility
4. Regarding phases of matter, which statement is true?
a. The kinetic, but not the potential, energy of a gas is higher than that of a liquid.
b. The kinetic and potential energy of a gas are higher than those of a liquid. *
c. the potential, but not the kinetic, energy of a gas is higher than that of a liquid.
d. The potential energy of a gas is always lower than that of a liquid.
5. The forces that will establish chemical bonds between atoms result from the interaction of attractive and repulsive forces between
a. protons and electrons b. electrons* c. electrons in the valence shell d. protons, but only when electrons are lost
6. An atom is to an element as a compound is to a
a. substance b. molecule* c. chemical d. mass
7. For the quantum number called ________, a value called _______ relates to a clockwise motion of a given electron.
a. orbital, shape b. electron spin, “up” c. orbital, sublevel* d. electron spin, “down”
8. The symbol for a boron isotope is 11/5 B. What is the mass number of this isotope?
a. 5 b. 6 c. 11* d. 16
9. The symbol for a boron isotope is 11/5 B. How many neutrons does this isotope have?
a. 5 b. 6 c. 11* d. 16
10. For the neon atom, the total number of electrons that can be found in the second principal energy level is
a. 4 b. 6* c. 8 d. 10
11. Which one of the following statements is true?
a. Fluorine, having seven valence electrons, can’t form a polar covalent bond. *
b. Hydrogen can’t attain a noble element configuration because it has only one electron. c. Fluorine, having four valence electrons, must form a non-polar covalent bond.
d. Hydrogen can attain a noble gas structure by sharing only two electrons.
12. The kilopascal is to pressure as the Kelvin scale is to the average ___ energy of any substance.
a. kinetic* b. potential c. volume d. mass
13. The most probable distance of an electron from an atom’s nucleus, expressed in whole numbers, refers specifically to
a. the principal quantum number. B. electron spin.* C. the Pauli exclusion principle. d. the sum of an atom’s sublevels.
14. We can describe ______ energy as the energy a body has depending on its position with relationship to another body.
a. heat* b. kinetic c. potential d. system
15. “Its bonds are strong, and its more or less non-mobile nuclei are surrounded by a sea of mobile electrons.” This sentence best expresses ______ bonds.
a. metallic* b. coordinate covalent c. ionic d. multiple covalent
16. According to Hund’s rule, electrons fill sublevels one electron at a time, and all _____ electrons around a given atom will have _____
a. paired, the same spin. B. unpaired, the same spin. C. paired, a single negative charge.* d. unpaired, equal valence energy.
17. Looking at the Periodic Table, we find that in every vertical group, electronegativity _____ as we move down and as atomic number increases. At the same time, moving horizontally across a row of the table, we find that electronegativity _____ as we move from left to right.
a. decreases, increases b. decreases, decreases* c. increases, decreases d. increases, increases
18. If two atoms form a molecule, the approximated distance between the nuclei of the two atoms is called the
a. covalent atomic radius b. bond length* c. bond length less the covalent atomic radius d. effective bond radius
19. Expressed as joules per gram degree, _____ heat capacity is a quantity necessary to raise the temperature of one gram of any substance by one degree Celsius.
a. Kelvin b. mass* c. differential d. specific
20. As determined by the work of physicist Niels Bohr, an atom emits energy when one of the electrons falls from a higher to a lower energy level. Following from this observation, the Bohr model also proposes that the difference between the two energy levels in such a case determines the
a. color of the electron b. frequency of the emitted radiation c. instability of the atom’s nucleus* d. mass of the emitted radiation
Part 2 – Chemical Families
1. If a small piece of sodium is dropped into water, it begins to react, forming hydrogen gas and sodium hydroxide. In the equation, 2Na (s) + 2H2O (I) -→ 2NaOH (aq) + H2 (g), the sodium hydroxide that is formed is a
a. compound in a solution b. precipitate* c. gas d. reactant
2. With the exception of the transition elements, Groups 3-12 in the Periodic Table, and the noble gases, Group 18, atomic radii _____ within periods, while atomic radii _____ within groups.
a. increase, decrease b. decrease, increase c. increase, remain roughly constant* d. decrease, remain roughly constant
3. Which oxide of nitrogen is responsible for the formation of ozone?
a. N2O b. NO2* c. NO d. N2O4
4. Which one of the following statements is correct regarding the naming of binary compounds?
a. The nonmetal is named first followed by the metal* b. If the compound consists of 2 nonmetals, the nonmetal with the higher electronegativitity is named 1st c. If the compound consists of 2 nonmetals, the nonmetal with the lower electronegativity is named 1st d. The nonmetal is named first followed by the metal with the ending “ate”
5. Using the Periodic Table for reference, what do boron, silicon, and arsenic have in common?
a. they all demonstrate the chemical properties of carbon* b. they’re all strong conductors of electricity c. they’re similar to transition elements d. they’re all metalloids.
6. Which one of the following elements is a noble gas?
a. nitrogen* b. oxygen c. neon d. hydrogen
7. The atomic number for aluminum is
a. 13* b. 14 c. 26.98 d. 26.9815
8. The group of elements that contains only alkaline earth metals is
a. 2* b. 15 c. 17 d. 18
9. Regarding the halogens, which statement is most accurate?
a. We find two s and five p electrons in the outer energy level of all of these elements *
b. the electronegativity of the halogens increases with atomic number
c. all the halogen elements form a noble gas octet of valence electrons with the element next to it in Group 16
d. the oxidation state of all halogens is +1
10. You would apply stock numbers only to compounds of metals and to compounds of a. sulfur b. oxygen c. helium d. hydrogen. *
11. Regarding the carbon family, which statement is true?
a. all carbon compounds are considered to be organic compounds b. one common carbon compound is a waste product of photosynthesis* c. in nature, silicon is found in a free state and isn’t an abundant element on Earth d. the higher atomic numbers in this family are associated with two common metals
12. Which of the following is clearly a polyatomic ion?
a. C6H12O6 b. NH4* c. NaN3 d. NA 1+
13. We can most accurately say of aluminum that it
a. oxidizes rapidly to form a protective coating against further deterioration b. is a poor conductor of electricity c. doesn’t readily conduct heat *d. is an alkaline earth metal
14. In the Periodic Table (omitting the transition elements), the trend with respect to numbers of valence electrons is
a. periodic with respect to atomic number, but generally increasing from right to left *
b. lower on the left and higher on the right c. periodic with respect to atomic number, but generally decreasing from left to right d. higher on the left and lower on the right
15. If the gram molecular mass of carbon is 12 and the gram molecular mass of chlorine is 35, the gram mass of one molar mass of carbon tetrachloride must be
a. 47 b. 83* c. 152 d. 196
16. Among the alkali metals, _____ placed in water will combine with H2O to produce hydrogen gas that burns with a violet flame.
a. magnesium *b. sodium c. potassium d. calcium
17. Metals and nonmetals form compounds called hydroxides, symbolized as XOH, where X stands for some metal or nonmetal. In which of the following situations would we find ions in solution such that the solution is acidic?
a. the bond between X and OH is broken *b. the bond between XO and H is broken c. Either H or OH takes on a positive charge d. the bonds of XOH remain unbroken
18. Comparing Group 1 & Group 2 elements, which statement about the alkaline earth metals is true?
*a. the increased atomic number of the Group 2 elements tends to shrink their atomic radii relative to Group 1 b. the alkaline earth metals form acids in water c. the higher ionization energy of the Group 2 elements makes them more reactive than the Group 1 elements d. Both Group 1 and Group 2 are composed of transition elements
19. Comparing an analysis reaction with a combination reaction, and assuming a total of three kinds of molecules in either kind of reaction, you would expect to find
a. two products on the right side of the equation in a combination reaction b. a single product on the right side of the equation in an analysis reaction c.* two products on the right side of the equation in a decomposition reaction d. a single product on the left side of the equation in a synthesis reaction
20. A reaction takes place between sodium chloride and hydrochloric acid. The products of this reaction are sodium sulfate (Na2SO4) and hydrochloric acid. What is the balanced equation that represents this reaction?
a. NaCl + H2SO4→ Na2SO4 + HCl b. 2NaCl + H2SO4 →Na2SO4 + HCl c.* 2NaCl + H2SO4 → Na2SO4 + 2HCl d. NaCl + H2SO4 → 2 Na2SO4 + 2HCl
Part 3 – The Nature of Chemical Reactions
1. Molarity is to moles of solute over liters of solution as molality is to
a. molar concentration over molal concentration b. moles of solute over kilograms of solvent c. molal concentration over molar concentration d. moles of solute over moles of solvent *
2. In describing an equilibrium reaction involving hydrogen gas, iodine gas, and hydrogen iodide gas, all of the statements about equation Q= [Hl]2 ÷ [H2] [l2] are true except for which one?
a. any solids are omitted from equilibrium expressions b*. the brackets refer to “concentration of …” c. coefficients from the original balanced equation (in this case, 2 Hl) become exponents d. the products go to the denominator, and the reactants go to the numerator
3. If the angle of collision between molecules A and B in a reaction is favorable, reaction energy is less than when the angle of collision is unfavorable. If you look up the typical activation energy for a given reaction in a table, the value you see will be for
a.* minimum activation energy b. maximum activation energy c. average activation energy d. the range of values between minimum & maximum activation energy
4. If a catalyst is used to alter the reaction rate of A + B ? AB, we can expect a/an
a. increase in ΔH b. increase in the activation energy that initiates the reaction c. decrease in ΔH d. decrease in the activation energy that initiates the reaction *
5. Regarding solutions and solids, which statement is true?
a. if the solvent is water, the crystal lattice energy of a solid is absorbed b. *hydration energy is related to the attractions between solute particles c. if the solvent is water, the crystal lattice energy of a solid is released d. hydration energy is related to the attractions between solvent particles
6. Avogadro’s number gives us the number of
a. atoms in any element or compound b. particles in a mole of any element or compound c. atoms in an element d. particles in a sample *
7. A chemical formula containing the simplest whole-number ratio between elements in a compound is called the _____ formula.
a. derivative* b. composition c. composition ratio d. empirical.
8. Which one of the following statements is correct← →
a. solubility of solids and liquids is affected by randomness and temperature b. increasing temperature and lowering pressure maximizes the solubility of a gas in a liquid c. energy has no affect on solubility d.* when a solid dissolves, the attractive forces are weakened, and entropy decreases
9. For which of the following must the empirical formula be written with only one subscript?
a. C6H6 b*. C5H12 c. C2H6 d. H2O2
10. Regarding electrolytes, all of the following statements are true except for which one?
a.* covalent bonds, such as those of sugar, make weak electrolytes in solution b. ionic compounds often form strong electrolytes when in solution c. ammonia is a weak electrolyte because it produces few mobile ions d. mobile ions formed as a result of dissociation cause solutions to conduct electricity
11. The equation for an equilibrium reactions is A + B AB. Following Le Chatelier’s principle, if the concentration of “A” is increased, then
a.* stress and equilibrium are not affected b. the equilibrium shifts to the left c. the equilibrium shifts to the right d. a smaller concentration of products is formed
12. If two immiscible liquids are joined in the same container, one liquid will rise to the top of the container because of its
a. *lower ionization energy b. lower density c. greater ionization energy d. greater density
13. The volume in liters at STP for 15 grams of helium is
a. 3.75 *L b. 56.25 L c. 84 L d. 89.6 L
14. Picture two gases in an equilibrium solution in a sealed container such that the total volume of the reactants, A + B, is equal to the total volume of the product, AB. If the volume of the container is reduced from V to ½ V, we would observe
a. that the system remains at equilibrium b. an increase in the rate of forward reaction and an increase in AB c. *a decrease in the rate of forward reaction and an increase in the concentration of reactants d. that the equilibrium constant (KEQ) increases only slightly with respect to the ration of product to reactants.
15. Picturing a sealed container of some solution, the temperature at which the vapor pressure of a liquid equals the pressure of the gas acting on the liquid is the
a. *colligative standard b. freezing point for that solution c. boiling point for that solution d. freezing or boiling point for that solution
16. Which statement best illustrates phase equilibrium?
a. *ice in a tray melts as the temperature goes up b. in a sealed container, water evaporates and condenses as the water level remains constant c. ice in a tray evaporates directly from solid to water vapor in a process of sublimation d. in a sealed container, two gases interact such that reverse reactions precede forward reactions
17. At 20º C, 100 grams of water can dissolve 72 grams of HCl. At this point, in terms of solubility, the solution is said to be
a. *supersaturated b. nearly saturated c. saturate d. balanced
18. The equilibrium constant is the ration of product concentration to reactant concentration at equilibrium. A reaction will likely go to completion if the equilibrium constant
a. *is very high b. is moderate c. is very low d. increases with rate of reaction
19. In the compound KClO3, what is the percent composition to the nearest whole number of potassium?
a. *29% b. 32% c. 35% d. 39%
20. In a lab experiment, we compare the rates of reactions between oxygen and a substance, S, that oxidizes at room temperature. In Experiment 1, we expose 5 grams of S to the air. In Experiment 2, we expose 5 grams of S to the air, but this time, S is ground into a powder. What can we expect to observe, and why?
a.* there will be no change in the reaction rates b. the reaction rate for Experiment 2 will be much slower due to increased surface area c. the reaction rate for Experiment 2 will be much faster due to the increased surface area d. the reaction rate for Experiment 1 will be much faster due to concentration of reactants.
Part 4 – Dynamics in Chemical Reactions
1. To figure out the exact pH of a solution, you’ll need to determine the
a. *concentration of OH- ions b. concentration of H+ ions relative to the concentration of OH- ions c. concentration of H+ ions d. ratio of OH- ions to H+ ions
2. In chemical reactions, which of the following is a factor that tends to increase entropy?
a.* high temperature b. being in a solid state c. high pressure d. small, simple molecules
3. When a chemist says that a salt such as potassium chloride is fused, he or she means that the substance is
a. *vaporized b. melted c. rapidly reduced d. rapidly oxidized
4. What occurs in the process of ionization?
a.* acids dissociate to produce hydroxide ions, as their only negative ions b. strong bases ionize almost completely yielding a maximum quantity of hydrogen ions c. stationary solid ions are produced d. ions are formed by a dissolved molecular substance
5. The direction of change in a reaction depends on the combined changes of entropy, heat of reaction, and temperature. If this is expressed as ΔG = ΔH – TΔS, what would it mean if the value for free energy (ΔG) is zero?
a. the reaction is spontaneous b. the reaction is in equilibrium c.* the reaction isn’t spontaneous d. no reaction is possible
6. What occurs in a reduction reaction?
a. there is no change in the oxidation state b. the oxidation state of an element increases c. a particle gains electrons d*. a particle loses electrons
7. What occurs in a reaction in which the reactant is a solid and the product is a gas?
a. there is no change in entropy b. the entropy change is most likely negative because the molecules in the solid state are more random than the molecules in the gaseous state c. the entropy decreases and the sign of ΔS most likely would be negative d.* ΔS most likely would be positive because a gas has greater entropy than a solid
8. If one species in a redox reaction undergoes oxidation, what happens to the other species?
a. *it must undergo oxidation b. it must undergo reduction c. it may undergo oxidation d. it may undergo reduction
9. Pure ammonia gas (NH3) contains no hydroxyl ions. However, ammonia takes on the characteristic slippery feel of a weak base in water solution because
a.* the NH ion has a negative charge b. the water-ammonia reaction produces OH- ions c. the NH ion is positive d. water is a strong electrolyte
10. Spontaneous chemical change is least likely to occur when there’s a/an
a. increase in potential energy accompanied by a decrease in entropy b. decrease in potential energy accompanied by a increase in entropy c. *increase in potential energy accompanied by a increase in entropy d. decrease in potential energy accompanied by a decrease in entropy
11. Determine the pH of a o.00001 M solution of the strong acid HNO3
a*. -1.3 b. 1.3 c. -5 d. 5
12. Consider the reaction: 2 Ag+ (aq) + Cu (s) → Cu2+ (aq) + 2 Ag (s). The half-reactions for this reaction would
a. show the oxidation and reduction of the reactants as separate reactions b. separate out the charges on each side of the equation c. show the loss of electrons in the reduction half-reaction d*. rebalance the charge values on either side of the equation
13. In a titration procedure, you have a solution of hydrochloric acid in your beaker and a solution of sodium hydroxide in the burette. At the equivalence point,
a. the concentrations of base and acid in the beaker will be saturated b. the ratio of positive to negative ions will be greater than 1 c. the ration of negative to positive ions will be greater than 1 d.* an equal number of moles of acid and base will have reacted within the beaker
14. Regarding oxidation numbers in redox reactions, which statement is true?
a. the algebraic sum of oxidation numbers in a molecule or compound is zero b. *loss of an electron results in a decrease in an oxidation number c. oxidation numbers in a redox reaction tend to shift from left to right d. in a redox reaction, oxidation numbers generally remain the same
15. Which of the following statements refers most directly to enthalpy?
a. in an endothermic reaction, the sign of ΔH is negative b. Potential energy decreases in an exothermic reaction c. molecules in a gas spin or tumble end over end d*. molecules in a heated metal vibrate more rapidly
16. In general, anode is to ______ as cathode is to ______, and a flow of electrons will go from _____ to _____
a. reduction, oxidation, anode, cathode b. reduction, oxidation, cathode, anode c. *oxidation, reduction, cathode, anode d. oxidation, reduction, anode, cathode
17. What characteristic is common of both acids and bases?
a.* both have a bitter taste b. both feel slippery to the touch c. both are electrolytes d. both have a sour taste
18. If you test a sample of water from a well, you’ll find it acidic if the pH is
a. 4 b.* 7 c. 8 d. 11
19. With respect to Bronsted-Lowry model of acids and bases, which statement is false?
a.* acids donate an electron pair b. water can act as a base c. acids donate 1 or more protons d. water can act as an acid
20. How much heat is released when 200 grams of sodium hydroxide dissolve in water?
a. -210 kJ b. *210 kJ c. -223 kJ d. 223 kJ
Part 5 – Organic and Nuclear Chemistry
1.Among _____ series of hydrocarbons, alkanes, _____, and alkynes make up distinct groups
a. *carbon-hydrogen, propanes b. homologous, alkenes c. carbon-hydrogen, alkenes d. homologous, propanes
2. Regarding nuclear reactions that release a great deal of energy, which statement is true?
a. in a fission chain reaction, a uranium nucleus struck by a high-energy neutron emits two neutrons b. nuclear fission releases more energy per unit mass than does a fusion reaction c. *nuclear reactors produce dangerous levels of air pollution d. a fusion reaction proceeds through the joining of two isotopes of hydrogen
3. concerning the saponification process, which statement is true?
a. the polar end of a soap molecule dissolves in oil b. the nonpolar end of a soap molecule dissolves in both oil and water c.* detergents with branched chains are biodegradable d. organic molecules that have polar and nonpolar properties are called detergents
4. Thinking about the uses of radioactive isotopes, which statement is true?
a. the iodine isotope, l-27, is used to diagnose thyroid disorders b.* radiation may be detected because it ionizes the atoms it affects c. it’s clearly understood that irradiating food kills bacteria and contaminates the food d. radioactive isotopes used in medical diagnoses have long lives and are quickly absorbed by the body.
5. Regarding types of organic reactions, which statement is false?
a. certain foods containing unsaturated molecules may be hydrogenated to minimize spoilage b. if an unsaturated compound acquires a halogen-like fluorine-the reaction is said to proceed by substitution c. *unsaturated organic compounds have one or more double or triple bonds d. if one hydrogen bond in a saturated organic compound is replaced by a bromine atom, we speak of substitution.
7. As to the binding energy of different atomic nuclei, it turns out that
a.* excepting radioactive elements, the most stable elements have mass numbers of 100 or higher b. as binding energies increase, the stability of nuclei decreases c. binding energies are strongest among the light elements with the exception of hydrogen d. the most stable elements have mass numbers of around 56
8. We can fairly say any of the following about carbon compounds except that
a. *most carbon compounds are ionic b. carbon atoms bond easily with other carbon atoms c. their covalent bonds make most carbon compounds molecular d. organic chemical reactions tend to be slow
9. Which statement is correct regarding neutron-to-proton ratios?
a. if the n/p ratio of an atom is greater than 1, it’s nearly always an isotope and is always very stable b. if the n/p ratio is greater than 1, the element is probably a heavier element and contains more protons than neutrons c.* if the n/p ratio is greater than 1, an element is always radioactive d. if the n/p ratio is 1, the element is likely to be a lighter element
10. Which of the following is associated with ß+ decay?
a. the parent and daughter nuclei still have the same n/p ratio b.* the ratio of neutrons to protons is too low for stability c. repulsion forces among large numbers of protons make the nucleus unstable d. the ratio of neutrons to protons is too high for stability
12. All of the following statements are true except that
a. the amount of radioactive carbon in your body increases at the time of death b.* radioactive carbon forms as atmospheric nitrogen is bombarded by high-energy neutrons from outer space c. the amount of radioactive carbon in the air remains roughly constant over time d. radioactive carbon is absorbed by living things in the form of carbon dioxide
13. When six protons and six neutrons unite to form a carbon atom, the net mass of the 12 nuclides decreases slightly. This _____ multiplied by _____ equals the nuclear binding energy of carbon 12.
a. mass defect, the atom’s mass b. mass difference, mc2 c. mass defect, mc2 d.* mass difference, the atom’s mass
14. If you pass radiation between two charged plates, which two kinds of radiation emissions will be attracted and bent toward a negative plate?
a.* positrons and alpha particles b. beta particles and gamma rays c. gamma rays and positrons d. alpha particles and beta particles
15. As to naming organic compounds, which statement is false?
a. the name 2, 3-dimethylpentane tell you there are two or three alkyl groups in the compound b. *the first thing you do in naming an organic compound is count the number of carbon atoms in a continuous chain c. carbon groups that aren’t part of the main carbon chain are called side chains d. the name 2, 3-dimethylpentane tells the location of methyl groups on the main carbon chain
16. The half-life of iridium- 131 is eight days. Atom by atom, it decays into an isotope of iodine. How much of 24 grams of iridium will be left after 24 days?
a. 6 grams b.* 4 grams c. 3 grams d. 0 grams
17. Which statement about functional groups is false?
a. a functional group in an organic compound typically dictates its chemical properties b. ethane and methane are examples of functional groups c. the notations (-0-) or (-OH) represent functional groups d.* amines and amides include nitrogen in their functional groups
18. Two organic compounds with the same numbers and kinds of atom but different structures
a. can’t include functional groups b. will have distinct molecular masses c. are called isomers d. *are called homologous compounds
19. If a hydrocarbon molecule includes two or more double bonds between carbon atoms, we would identify it as a/an
a. complex alkane b.* polyolefin alkyne c. alkyne olefin d. polyolefin alkene
Except for #1, the first three look ok. The best answer there is c (I think you picked b).
discuss Leblanc's contribution to industrial chemistry.
trace hiw the succeeding chemists got rid of the problems associated with Leblanc's process.
Has anybody used any of these answers? I used three of them and got them wrong...
No one's going to help you mr.
we can most accurately say of aluminum that it..
The formula is C3H6Br2. If the compounds is called 1,2-dibromopropane, A, B and C must be...this is question 20, from which there was no answer to this question. Need to know the answer,please.