January 2013 Chemistry Regents #31-40

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Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions 51 Questions 52-54 Questions 55-58 Questions 59-61 Questions 62-65 Questions 66-69

Questions 70-72 Questions 73-76 Questions 77-79 Questions 80-82 Questions 83-85

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Explanations

31 Which electron configuration represents a selenium atom in an excited state?

(1) 2-7-18-6

(2) 2-7-18-7

(3) 2-8-18-6

(4) 2-8-18-7

2Linkmust have 34 electrons

moving one to a higher energy level

NOT the configuration in the Reference Tables

32 When the hydronium ion concentration of a solution is increased by a factor of 10, the pH value of the solution

(1) decreases 1 pH unit

(2) decreases 10 pH units

(3) increases 1 pH unit

(4) increases 10 pH units

1Linkincrease by 10 pH changes by 1

hydronium is H3O+ so it becomes more acidic, pH decrease

33 In the formula XF2, the element represented by X can be classified as a

(1) Group 1 metal

(2) Group 2 metal

(3) Group 1 nonmetal

(4) Group 2 nonmetal

2LinkX has a charge of 2+, because each F is 1-group 2

 

34 Which compound has the smallest percent composition by mass of chlorine?

(1) HCl    (3) LiCl

(2) KCl   (4) NaCl

2Linkthe most massive will have the smallest percent of Cl

35 Given the incomplete equation representing a reaction:

2C2H14 + ____ O2 --> 12 CO2 + 14 H2O

What is the coefficient of O2 when the equation is completely balanced using the smallest whole-number coefficients?

(1) 13

(2) 14

(3) 19

(4) 26

3Linkadd up the oxygen's on the right and divide by 2 to get the coefficient on the left

36 What is the oxidation number of iodine in KIO4?

(1) +1 (3) +7

(2) -1 (4) - 7

3Linksince each O is -2 and K is +1 I must be +7

 

37 What is the chemical formula for zinc carbonate?

(1) ZnCO3

(2) Zn(CO3)2

(3) Zn2CO3

(4) Zn3CO3

1Linkuse table E and the charges...see link

38 Which statement explains why a molecule of CH4 is nonpolar?

(1) The bonds between the atoms in a CH4 molecule are polar.

(2) The bonds between the atoms in a CH4 molecule are ionic.

(3) The geometric shape of a CH4 molecule distributes the charges symmetrically.

(4) The geometric shape of a CH4 molecule distributes the charges asymmetrically.

3Link

lower the volume first

SNAP= symmetrical nonpolar asymmetrical polar

 

39 Which atom in the ground state has the same electron configuration as a calcium ion, Ca2+, in the ground state?

(1) Ar

(2) K

(3) Mg

(4) Ne

1LinkCa2+ has 18 electrons

Atoms of Ar have 18 protons and 18 electrons

atoms are neutral

40 In the compound KHSO4, there is an ionic bond between the

(1) KH+ and SO42- ions

(2) KHSO3+ and O2- ions

(3) K+ and HS- ions

(4) K+ and HSO4- ions

4LinkHSO4- is a polyatomic ion

Table E

Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50

Questions 51 Questions 52-54 Questions 55-58 Questions 59-61 Questions 62-65 Questions 66-69

Questions 70-72 Questions 73-76 Questions 77-79 Questions 80-82 Questions 83-85

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