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Physical Setting / Chemistry - New York Regents January 2015

Formats Worksheet / Test Paper Quiz Review

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Part A
Answer all questions in this part.
   Directions (1–30): For each statement or question, record on your separate answer sheet the number of the
word or expression that, of those given, best completes the statement or answers the question. Some questions
may require the use of the 2011 Edition Reference Tables for Physical Setting/Chemistry.

1.
1 According to the modern model of the atom, the
  nucleus of an atom is surrounded by one or more
  (1) electrons             (3) positrons
  (2) neutrons              (4) protons
Answer: 1

2.
2 Which particle has a mass of approximately
  1 atomic mass unit?
  (1) an alpha particle (3) an electron
  (2) a beta particle   (4) a neutron
Answer: 4

3.
3 A specific amount of energy is emitted when
  excited electrons in an atom in a sample of an
  element return to the ground state. This emitted
  energy can be used to determine the
  (1) mass of the sample
  (2) volume of the sample
  (3) identity of the element
  (4) number of moles of the element
Answer: 3


4.
4 According to the wave-mechanical model, an
  orbital is defined as the
  (1) circular path for electrons
  (2) circular path for neutrons
  (3) most probable location of electrons
  (4) most probable location of neutrons
Answer: 3

5.
5 All phosphorus atoms have the same
  (1) atomic number
  (2) mass number
  (3) number of neutrons plus the number of
      electrons
  (4) number of neutrons plus the number of
      protons
Answer: 1

6.
6 At STP, which element is a good conductor of
  electricity?
  (1) chlorine           (3) silver
  (2) iodine             (4) sulfur
Answer: 3

7.
7 Which phrase describes the molecular structure
  and properties of two solid forms of carbon,
  diamond and graphite?
  (1) the same molecular structures and the same
      properties
  (2) the same molecular structures and different
      properties
  (3) different molecular structures and the same
      properties
  (4) different molecular structures and different
      properties
Answer: 4

8.
8 Which quantity is equal to one mole of Au?
  (1) the atomic mass in grams
  (2) the atomic number in grams
  (3) the mass of neutrons in grams
  (4) the number of neutrons in grams
Answer: 1

9.
9 Given the balanced equation representing the
  reaction between methane and oxygen:
          CH4 + 2O2 → CO2 + 2H2O
  According to this equation, what is the mole
  ratio of oxygen to methane?

Answer: 4

10.
10 Which list includes three    types of chemical
   reactions?
   (1) decomposition, single    replacement, and
       solidification
   (2) decomposition, single    replacement, and
       double replacement
   (3) solidification, double   replacement, and
       decomposition
   (4) solidification, double   replacement, and
       single replacement
Answer: 2

11.
11 Which compound has the greatest percent
   composition by mass of sulfur?
   (1) BaS                 (3) MgS
   (2) CaS                 (4) SrS
Answer: 3

12.
12 Two molecules of HBr collide and then form H2
   and Br2. During the collision, the bonds in the
   HBr molecules are
   (1) broken as energy is absorbed
   (2) broken as energy is released
   (3) formed as energy is absorbed
   (4) formed as energy is released
Answer: 1

13.
13 Which atom in the ground state has a stable
   electron configuration?
   (1) carbon              (3) neon
   (2) magnesium           (4) oxygen
Answer: 3

14.
14 Which statement describes a multiple covalent
   bond?
   (1) Two electrons are shared.
   (2) Four electrons are shared.
   (3) Two electrons are transferred.
   (4) Four electrons are transferred.
Answer: 2

15.
15 The electronegativity difference between the
   atoms in a molecule of HCl can be used to
   determine
   (1) the entropy of the atoms
   (2) the atomic number of the atoms
   (3) the first ionization energy of the atoms
   (4) the polarity of the bond between the two
       atoms
Answer: 4

16.
16 Which two gases can not be broken down by
   chemical means?
   (1) CO and He         (3) Xe and He
   (2) CO and NH3        (4) Xe and NH3
Answer: 3

17.
17 Two substances in a mixture differ in density
   and particle size. These properties can be used to
   (1) separate the substances
   (2) chemically combine the substances
   (3) determine the freezing point of the mixture
   (4) predict the electrical conductivity of the
       mixture
Answer: 1

18.
18 Which unit is used to express an amount of
   thermal energy?
   (1) gram              (3) joule
   (2) mole              (4) pascal
Answer: 3

19.
19 Under which conditions of temperature and
   pressure does a real gas behave most like an
   ideal gas?
   (1) low temperature and low pressure
   (2) low temperature and high pressure
   (3) high temperature and low pressure
   (4) high temperature and high pressure
Answer: 3

20.
20 According to the kinetic molecular theory for an
   ideal gas, all gas particles
   (1) are in random, constant, straight-line motion
   (2) are separated by very small distances relative
       to their sizes
   (3) have strong intermolecular forces
   (4) have collisions that decrease the total energy
       of the system
Answer: 1

21.
21 Which mathematical expression represents the
   heat of reaction for a chemical reaction?
   (1) (the heat of fusion) – (the heat of vaporization)
   (2) (the heat of vaporization) – (the heat of fusion)
   (3) (the potential energy of the products) – (the
       potential energy of the reactants)
   (4) (the potential energy of the reactants) – (the
       potential energy of the products)
Answer: 3

22.
22 At 101.3 kPa and 298 K, a 1.0-mole sample of
   which compound absorbs the greatest amount
   of heat as the entire sample dissolves in water?
   (1) LiBr                 (3) NaOH
   (2) NaCl                 (4) NH4Cl
Answer: 4

23.
23 For a reaction at equilibrium, which change can
   increase the rates of the forward and reverse
   reactions?
   (1) a decrease in the concentration of the
       reactants
   (2) a decrease in the surface area of the products
   (3) an increase in the temperature of the system
   (4) an increase in the activation energy of the
       forward reaction
Answer: 3

24.
24 Which reaction produces ethanol?
   (1) combustion         (3) fermentation
   (2) esterification     (4) polymerization
Answer: 3

25.
25 The chemical process in which electrons are
   gained by an atom or an ion is called
   (1) addition             (3) reduction
   (2) oxidation            (4) substitution
Answer: 3

26.
26 Which process occurs in an operating voltaic cell?
   (1) Electrical energy is converted to chemical
       energy.
   (2) Chemical energy is converted to electrical
       energy.
   (3) Oxidation takes place at the cathode.
   (4) Reduction takes place at the anode.
Answer: 2

27.
27 What can be explained by the Arrhenius theory?
   (1) the behavior of many acids and bases
   (2) the effect of stress on a phase equilibrium
   (3) the operation of an electrochemical cell
   (4) the spontaneous decay of some nuclei
Answer: 1

28.
28 According to one acid-base theory, a water
   molecule acts as an acid when the molecule
   (1) donates an H+ ion
   (2) accepts an H+ ion
   (3) donates an OH- ion
   (4) accepts an OH- ion
Answer: 1

29.
29 Positrons and beta particles have
   (1) the same charge and the same mass
   (2) the same charge and different masses
   (3) different charges and the same mass
   (4) different charges and different masses
Answer: 3

30.
30 Which term identifies a type of nuclear reaction?
   (1) transmutation         (3) deposition
   (2) neutralization        (4) reduction
Answer: 1


Part B–1
Answer all questions in this part.
   Directions (31–50): For each statement or question, record on your separate answer sheet the number of the
word or expression that, of those given, best completes the statement or answers the question. Some questions
may require the use of the 2011 Edition Reference Tables for Physical Setting/Chemistry.

31.
31 What is the number of electrons in an Al3+ ion?
   (1) 10                  (3) 3
   (2) 13                  (4) 16
Answer: 1

32.
32 The valence electron of which atom in the ground
   state has the greatest amount of energy?
   (1) cesium               (3) rubidium
   (2) lithium              (4) sodium
Answer: 1

33.
33 The numbers of protons and neutrons in each of
   four different atoms are shown in the table
   below.
              Protons and Neutrons in
               Four Different Atoms
        Atom     Number of      Number of
                  Protons       Neutrons
          A           8              8
          D           9              9
          E           9             10
          G          10             10
   Which two atoms represent isotopes of the same
   element?
   (1) A and D            (3) E and D
   (2) A and G            (4) E and G
Answer: 3

34.
34 Which elements have the most similar chemical
   properties?
   (1) boron and carbon
   (2) oxygen and sulfur
   (3) aluminum and bromine
   (4) argon and silicon
Answer: 2

35.
35 Which element reacts with oxygen to form ionic
   bonds?
   (1) calcium             (3) chlorine
   (2) hydrogen            (4) nitrogen
Answer: 1

36.
36 The table below gives the atomic mass and the
   abundance of the two naturally occurring
   isotopes of chlorine.
  Naturally Occurring Isotopes of Chlorine
               Atomic Mass of        Natural
   Isotopes     the Isotope         Abundance
                   (u)                (%)
      35Cl         34.97             75.76
      37Cl         36.97             24.24
   Which numerical setup can be used to calculate
   the atomic mass of the element chlorine?
   (1) (34.97 u)(75.76) + (36.97 u)(24.24)
   (2) (34.97 u)(0.2424) + (36.97 u)(0.7576)
   (3) (34.97 u)(0.7576) + (36.97 u)(0.2424)
   (4) (34.97 u)(24.24) + (36.97 u)(75.76)
Answer: 3

37.
37 Which general trends in first ionization energy
   and electronegativity values are demonstrated
   by Group 15 elements as they are considered in
   order from top to bottom?
   (1) The first ionization energy decreases and
       the electronegativity decreases.
   (2) The first ionization energy increases and the
       electronegativity increases.
   (3) The first ionization energy decreases and
       the electronegativity increases.
   (4) The first ionization energy increases and the
       electronegativity decreases.
Answer: 1

38.
38 An aluminum sample has a mass of 80.01 g and
   a density of 2.70 g/cm3. According to the data, to
   what number of significant figures should the
   calculated volume of the aluminum sample be
   expressed?
   (1) 1                     (3) 3
   (2) 2                     (4) 4
Answer: 3

39.
39 Given four particle models:
Which two models can be classified as elements?
(1) I and II           (3) II and III
(2) I and IV           (4) II and IV
Answer: 3

40.
40 After being thoroughly stirred at 10.°C, which
   mixture is heterogenous?
   (1) 25.0 g of KCl and 100. g of H2O
   (2) 25.0 g of KNO3 and 100. g of H2O
   (3) 25.0 g of NaCl and 100. g of H2O
   (4) 25.0 g of NaNO3 and 100. g of H2O
Answer: 2

41.
41 Which two compounds are electrolytes?
   (1) KOH and CH3COOH
   (2) KOH and C5H12
   (3) CH3OH and CH3COOH
   (4) CH3OH and C5H12
Answer: 1

42.
42 Which statement explains why a CO2 molecule
   is nonpolar?
   (1) Carbon and oxygen are both nonmetals.
   (2) Carbon and oxygen have different
       electronegativities.
   (3) The molecule has a symmetrical distribution
       of charge.
   (4) The molecule has an asymmetrical distribution
       of charge.
Answer: 3

43.
43 Which temperature change indicates an increase
   in the average kinetic energy of the molecules in
   a sample?
   (1) 15°C to 298 K         (3) 305 K to 0°C
   (2) 37°C to 273 K         (4) 355 K to 25°C
Answer: 1

44.
44 Given the particle diagram:
Which substance at STP can be represented by
this particle diagram?
(1) N2                 (3) Mg
(2) H2                 (4) Kr
Answer: 3

45.
45 Which type of equilibrium exists in a sealed flask
   containing Br2(ℓ) and Br2(g) at 298 K and 1.0 atm?
   (1) static phase equilibrium
   (2) static solution equilibrium
   (3) dynamic phase equilibrium
   (4) dynamic solution equilibrium
Answer: 3

46.
46 What are the products when potassium hydroxide
   reacts with hydrochloric acid?
   (1) KH(s), Cl+(aq), and OH-(aq)
   (2) K(s), Cl2(g), and H2O(ℓ)
   (3) KCl(aq) and H2O(ℓ)
   (4) KOH(aq) and Cl2(g)
Answer: 3

47.
47 In a titration, 20.0 milliliters of a 0.150 M
   NaOH(aq) solution exactly neutralizes 24.0
   milliliters of an HCl(aq) solution. What is the
   concentration of the HCl(aq) solution?
   (1) 0.125 M              (3) 0.250 M
   (2) 0.180 M              (4) 0.360 M
Answer: 1

48.
48 What fraction of a Sr-90 sample remains
   unchanged after 87.3 years?

Answer: 4

49.
49 Which potential energy diagram represents the change in potential energy that occurs when a catalyst is
   added to a chemical reaction?

Answer: 2

50.
50 Which balanced equation represents a spontaneous radioactive decay?

Answer: 4


Part B–2
Answer all questions in this part.
   Directions (51–65): Record your answers in the spaces provided in your answer booklet. Some questions
may require the use of the 2011 Edition Reference Tables for Physical Setting/Chemistry.

51.
Base your answers to questions 51 through 53 on the information below and on your knowledge of chemistry.
         The balanced equation below represents the reaction of glucose, C6H12O6, with oxygen
     at 298 K and 101.3 kPa.
                             C6H12O6(s) + 6O2(g) → 6CO2(g) + 6H2O(ℓ)
     51 Determine the mass of CO2 produced when 9.0 grams of glucose completely reacts with
        9.6 grams of oxygen to produce 5.4 grams of water. [1]
Answer: MODEL ANSWER GIVEN BELOW
51 [1] Allow 1 credit for 13.2 g or for any value from 13.155 g to 13.2042 g, inclusive.


52.
52 Compare the entropy of the reactants to the entropy of the products. [1]
Answer: MODEL ANSWER GIVEN BELOW
52 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The entropy of the reactants is less than the entropy of the products.
             The reactants are more ordered.
             The products have greater entropy.


53.
53 Write the empirical formula for glucose. [1]
Answer: MODEL ANSWER GIVEN BELOW
53 [1] Allow 1 credit for CH2O. The order of the elements can vary.


54.
Base your answers to questions 54 and 55 on the information below and on your knowledge of chemistry.
          The diagram below represents a cylinder with a movable piston. The cylinder contains
      1.0 liter of oxygen gas at STP. The movable piston in the cylinder is pushed downward
      at constant temperature until the volume of O2(g) is 0.50 liter.
54 Determine the new pressure of O2(g) in the cylinder, in atmospheres. [1]
Answer: MODEL ANSWER GIVEN BELOW
54 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             2 atm
             2.0 atm


55.
55 State the effect on the frequency of gas molecule collisions when the movable piston is
   pushed farther downward into the cylinder. [1]
Answer: MODEL ANSWER GIVEN BELOW
55 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             When the piston is moved farther into the cylinder, the frequency of collisions between the
             molecules increases.
             There will be more collisions per second.
             increased frequency


56.
Base your answers to questions 56 through 58 on the information below and on your knowledge of chemistry.
         The formulas and the boiling points at standard pressure for ethane, methane,
      methanol, and water are shown in the table below.
                               Information for Four Compounds
56 Identify the compound that has the strongest intermolecular forces. [1]
Answer: MODEL ANSWER GIVEN BELOW
56 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             H2O
             water


57.
57 State the change in potential energy that takes place in a sample of methane as it boils
   at -161.5°C. [1]
Answer: MODEL ANSWER GIVEN BELOW
57 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             As liquid methane boils, the potential energy of the sample increases.
             Potential energy increases.
             higher PE


58.
58 Explain, in terms of molecular polarity, why the solubility of methanol in water is
   greater than the solubility of methane in water. [1]
Answer: MODEL ANSWER GIVEN BELOW
58 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Methanol and water molecules are polar, but methane molecules are nonpolar.
             The compounds methanol and water have similar polarities.


59.
Base your answers to questions 59 through 61 on the information below and on your knowledge of chemistry.
         The diagrams below represent ball-and-stick models of two molecules. In a ball-and-stick
      model, each ball represents an atom, and the sticks between balls represent chemical bonds.
59 Draw a Lewis electron-dot diagram for an atom of the element present in all organic
   compounds. [1]
Answer: MODEL ANSWER GIVEN BELOW
59 [1] Allow 1 credit. The positions of the dots can vary.
        Examples of 1-credit responses:


60.
60 Explain, in terms of carbon-carbon bonds, why the hydrocarbon represented in diagram B
   is saturated. [1]
Answer: MODEL ANSWER GIVEN BELOW
60 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The molecule in diagram B has only single carbon-carbon bonds.
             There are no multiple bonds between the carbon atoms.
             Cannot add more H atoms to the C atoms because all C-C bonds are single.


61.
61 Explain why the molecules in diagrams A and B are isomers of each other. [1]
Answer: MODEL ANSWER GIVEN BELOW
61 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Both molecules have the same molecular formula, but have different structural formulas.
             Both molecules are composed of 5 carbon atoms and 12 hydrogen atoms, but differ in the
             arrangement of their atoms.


62.
Base your answers to questions 62 and 63 on the information below and on your knowledge of chemistry.
          The nuts, bolts, and hinges that attach some gates to a playground fence can be made
      of iron. The iron can react with oxygen in the air. The unbalanced equation representing
      this reaction is shown below.
                                     Fe(s) + O2(g) → Fe2O3(s)
      62 Balance the equation in your answer booklet for the reaction, using the smallest
         whole-number coefficients. [1]
Answer: MODEL ANSWER GIVEN BELOW
62 [1] Allow 1 credit for


63.
63 Determine the change in oxidation state for oxygen in this reaction. [1]
Answer: MODEL ANSWER GIVEN BELOW
63 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             From 0 to -2
             From 0 to 2-
             From zero to negative two


64.
Base your answers to questions 64 and 65 on the information below and on your knowledge of chemistry.
         The pH of various aqueous solutions are shown in the table below.
                              pH of Various Aqueous Solutions
                                      Aqueous
                                     Solution          pH
                                      
                                    HCl(aq)             2
                                    HC2H3O2(aq)          3
                                    NaCl(aq)            7
                                    NaOH(aq)           12
      64 Complete the table in your answer booklet by writing the color of thymol blue in the
         NaCl(aq) and in the NaOH(aq) solutions. [1]
Answer: MODEL ANSWER GIVEN BELOW
64 [1] Allow 1 credit.
        Example of a 1-credit response:
              Aqueous      Color of
              Solution   Thymol Blue
              NaCl(aq)      yellow
              NaOH(aq)      blue


65.
65 State how many times greater the hydronium ion concentration in the HCl(aq) is than
   the hydronium ion concentration in the HC2H3O2(aq). [1]
Answer: MODEL ANSWER GIVEN BELOW
65 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             10
             ten
             tenfold
             10 times



Part C
Answer all questions in this part.
   Directions (66–85): Record your answers in the spaces provided in your answer booklet. Some questions
may require the use of the 2011 Edition Reference Tables for Physical Setting/Chemistry.

66.
Base your answers to questions 66 through 68 on the information below and on your knowledge of chemistry.
          There are six elements in Group 14 on the Periodic Table. One of these elements has
      the symbol Uuq, which is a temporary, systematic symbol. This element is now known as
      flerovium.
      66 Identify an element in Group 14 that is classified as a metalloid. [1]
Answer: MODEL ANSWER GIVEN BELOW
66 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Si
             germanium
             element 32


67.
67 Explain, in terms of electron shells, why each successive element in Group 14 has a larger
   atomic radius, as the elements are considered in order of increasing atomic number. [1]
Answer: MODEL ANSWER GIVEN BELOW
67 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The atomic radius of these elements increases down the group because each successive element
             has one more electron shell.
             The number of shells per atom increases.


68.
68 State the expected number of valence electrons in an atom of the element flerovium in
   the ground state. [1]
Answer: MODEL ANSWER GIVEN BELOW
68 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             4
             four
             4e-
             four valence electrons


69.
Base your answers to questions 69 through 72 on the information below and on your knowledge of chemistry.
          A student made a copper bracelet by hammering a small copper bar into the desired
      shape. The bracelet has a mass of 30.1 grams and was at a temperature of 21°C in the
      classroom. After the student wore the bracelet, the bracelet reached a temperature of 33°C.
      Later, the student removed the bracelet and placed it on a desk at home, where it cooled
      from 33°C to 19°C. The specific heat capacity of copper is 0.385 J/g•K.
      69 Explain, in terms of heat flow, the change in the temperature of the bracelet when
         the student wore the bracelet. [1]
Answer: MODEL ANSWER GIVEN BELOW
69 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The bracelet temperature increased because heat flowed from the body to the copper.
             Energy is tranferred from the student to the bracelet.
             Heat is absorbed by the bracelet.


70.
70 Determine the number of moles of copper in the bracelet. [1]
Answer: MODEL ANSWER GIVEN BELOW
70 [1] Allow 1 credit for 0.474 mol or for any value from 0.47 mol to 0.47402 mol, inclusive, or for 0.5 mol.


71.
71 Show a numerical setup for calculating the amount of heat released by the bracelet as
   it cooled on the desk. [1]
Answer: MODEL ANSWER GIVEN BELOW
71 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             q = (30.1 g)(0.385 J/g•K)(19°C - 33°C)
             (30.1 g)(306 K - 292 K)(0.385 J/g•K)
             (0.385)(30.1)(14)


72.
72 Explain, in terms of chemical activity, why copper is a better choice than iron to make
   the bracelet. [1]
Answer: MODEL ANSWER GIVEN BELOW
72 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Copper is less chemically active than iron, so copper is less likely to react with substances in the
             air or on the skin.
             Iron is more active.
             Fe oxidizes more easily.


73.
Base your answers to questions 73 through 75 on the information below and on your knowledge of chemistry.
          Seawater contains dissolved salts in the form of ions. Some of the ions found in seawater
      are Ca2+, Mg2+, K+, Na+, Cl-, HCO3-, and SO42-.
          An investigation was conducted to determine the concentration of dissolved salts in
      seawater at one location. A 300.-gram sample of the seawater was placed in an open
      container. After a week, all the water had evaporated and 10. grams of solid salts remained
      in the container.
      73 Determine the concentration, expressed as percent by mass, of the dissolved salts in the
         original sample of seawater. [1]
Answer: MODEL ANSWER GIVEN BELOW
73 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             3.3%
             3%
             3.3333%


74.
74 At standard pressure, compare the freezing point of seawater to the freezing point of
   distilled water. [1]
Answer: MODEL ANSWER GIVEN BELOW
74 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Water has a higher freezing point than seawater.
             Seawater’s is lower.


75.
75 Explain why the evaporation that occurred during the investigation is an endothermic
   process. [1]
Answer: MODEL ANSWER GIVEN BELOW
75 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Energy is needed to overcome the intermolecular forces.
             Energy is required to change liquid water to water vapor.
             The heat of vaporization is positive.


76.
Base your answers to questions 76 through 78 on the information below and on your knowledge of chemistry.
           A student makes an aqueous solution of lactic acid. A formula for one form of lactic acid
      is shown below.
   The solution is placed in a sealed flask to be used in a laboratory investigation. The
equation below represents the lactic acid equilibrium system in the flask.
76 Identify one organic functional group in a molecule of lactic acid. [1]
Answer: MODEL ANSWER GIVEN BELOW
76 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
        alcohol group
        acid
        hydroxyl
        carboxyl
Note: Do not allow credit for OH- or hydroxide.


77.
77 Explain, in terms of the reaction rates, why the concentrations of the reactants and
   products remain constant in this system. [1]
Answer: MODEL ANSWER GIVEN BELOW
77 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The rate of the forward reaction equals the rate of the reverse reaction.
             The reaction rates are the same at equilibrium.


78.
78 Explain, in terms of LeChatelier’s principle, why increasing the concentration of H+(aq)
   increases the concentration of lactic acid. [1]
Answer: MODEL ANSWER GIVEN BELOW
78 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The stress of adding H+ ions shifts the equilibrium to the left, producing more lactic acid.
             Increasing the concentration of H+(aq) favors the reverse reaction.
             More H+ ions collide with lactate ions, shifting the equilibrium left.


79.
Base your answers to questions 79 through 81 on the information below and on your knowledge of chemistry.
          Copper can be used for water pipes in homes. When the pipes corrode, copper atoms
      oxidize to form Cu2+ ions in the water.
          A homeowner has a water quality report prepared for a sample of water taken from pipes
      in the home. According to the report, the 550.-gram sample contains 6.75 ϫ 10-4 gram
      of dissolved Cu2+ ions.
      79 Using the key in your answer booklet, draw two water molecules in the box, showing
         the orientation of each water molecule toward the Cu2+ ion. [1]
Answer: MODEL ANSWER GIVEN BELOW
79 [1] Allow 1 credit. Acceptable responses must show at least two water molecules. The oxygen atom of
       each water molecule must face toward the copper ion.
        Examples of 1-credit responses:


80.
80 Show a numerical setup for calculating the concentration, in parts per million, of
   dissolved Cu2+ ions in the sample of water tested. [1]
Answer: MODEL ANSWER GIVEN BELOW
80 [1] Allow 1 credit. Acceptable responses include, but are not limited to:


81.
81 Write a balanced half-reaction equation for the corrosion that forms the Cu2+ ions. [1]
Answer: MODEL ANSWER GIVEN BELOW
81 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             Cu → Cu2+ + 2e-
             Cu - 2e- → Cu+2


82.
Base your answers to questions 82 through 85 on the information below and on your knowledge of chemistry.
          A breeder reactor is one type of nuclear reactor. In a breeder reactor, uranium-238 is
      transformed in a series of nuclear reactions into plutonium-239.
          The plutonium-239 can undergo fission as shown in the equation below. The X represents
      a missing product in the equation.
82 Determine the number of neutrons in an atom of the uranium isotope used in the
   breeder reactor. [1]
Answer: MODEL ANSWER GIVEN BELOW
82 [1] Allow 1 credit for 146.


83.
83 Based on Table N, identify the decay mode of the plutonium radioisotope produced in
   the breeder reactor. [1]
Answer: MODEL ANSWER GIVEN BELOW
83 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             alpha


84.
84 Compare the amount of energy released by 1 mole of completely fissioned plutonium-239
   to the amount of energy released by the complete combustion of 1 mole of methane. [1]
Answer: MODEL ANSWER GIVEN BELOW
84 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
             The fission of one mole of Pu-239 releases much more energy than the combustion of one mole
             of CH4.
             The energy released during the chemical reaction is less than the energy released during the
             nuclear reaction.


85.
85 Write a notation for the nuclide represented by missing product X in this equation. [1]
Answer: MODEL ANSWER GIVEN BELOW
85 [1] Allow 1 credit. Acceptable responses include, but are not limited to:
cerium-144
Ce-144



  Try the Quiz :     Physical Setting / Chemistry - New York Regents January 2015


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