June 2012 Chemistry Regents #31-40

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31 An atom in the ground state has two electrons in its first shell and six electrons in its second shell. What is the total number of protons in the nucleus of this atom?(1) 5     (2) 2     (3)  7   (4)  84linkAtom implies p=e

there are 8 electrons so 8 protons

32 A bromine atom in an excited state could have an electron configuration of

(1)2-8-18-6     (2)   2-8-18-7    (3) 2-8-17-7    (4)  2-8-17-8

4linkneeds 35 electrons

promoted an electron from the 3rd energy level to the 4th.

33 The atomic masses and the natural abundances of the naturally occurring isotopes of lithium are shown in the table below.

Which numerical setup can be used to determine the atomic mass of lithium?

(1)  (0.075)(6.02u) + (0.925)(7.02u)

(2)  (0.925)(6.02u) + (0.075)(7.02u)

(3)  (7.5)(6.02u) + (92.5)(7.02u)

(4)  (92.5)(6.02u) + (7.5)(7.02u)

1linkweighted average

 

mass x percent (as a decimal) + mass x percent (as a decimal)

 

34 Element X reacts with chlorine to form an ionic compound that has a formula of XCl2. To which group could element X belong?

(1) Group 1 (2) Group 2  (3) Group 13 (4) Group 15

2linkthe oxidation number for X is +2

X will be in group 2

35 Which general trend is found in Period 3 as the elements are considered in order of increasing atomic number?

(1) increasing atomic radius   (2) increasing electronegativity

(3) decreasing atomic mass  (4) decreasing first ionization energy

2linkgoing from left to right on the PT electronegativity increases
36 Given the formula for a compound:

Which molecular formula and empirical formula  represent this compound?

(1) C2HNO2 and CHNO   (2)  C2HNO2 and C2HNO2 

(3)  C4H2N2O4 and CHNO  (4)  C4H2N2O4 and C2HNO2 

4linkcount each atom for the molecular formula

 

find the lowest ratio of atoms for the empirical formula

 

37 What is the gram-formula mass of (NH4)3PO4?

(1) 112g/mol   (2) 121g/mol   (3)  149g/mol  (4)  242g/mol

3link(3 x14 ) + (12 x 1)  + (30)  +(4x16)=149

 

38 In the ground state, which atom has a completely filled valence electron shell?

(1) C   (2)  V    (3)   Ne    (4)Sb

3linkNoble Gases have a full valence shell

 

The bonds between which two atoms has the greatest degree of polarity?

(1)  C and C  (2) C and O  (3)  H and C  (4)  H and O

4linkBond Polarity depends on electronegativity difference (table S)

Large the difference the more polar the bond

During which time interval is the average kinetic energy of the particles of the substance constant while the potential energy of the particles increases?

(1) AC  (2)  BC  (3) CD   (4)DF

2linkplateaus are where phase changes occur and where potential energy changes and KE stays the same

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

Question 51 Questions 52-55 Questions 56-59 Questions 60-62 Questions 63-65 Questions 66-68 Questions 69-71 Questions 72-75  Questions 76-78  Questions 79-81  Questions 82-85

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