August 2005 Chemistry Regents #31-40

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

 

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Answer Explanations
31 The percentage by mass of Br in the compound
AlBr3 is closest to
(1) 10.%    (3) 75%
(2) 25%     (4) 90.%
4 (3(79.9) /(3(79.9) +27)) x 100%
32 Which symbol represents a particle with a total of 10 electrons?
(1) N         (3) Al
(2) N3+    (4) Al3+
4 Al = 13 electrons

Al3+ loses 3 electrons

33 Which electron configuration represents an atom of aluminum in an excited state?
(1) 2-7-4         (3) 2-8-3
(2) 2-7-7         (4) 2-8-6
1 Al = 13 electrons

promote 1 electron

2-8-3  ==> 2-7-4

34 At STP, an element that is a brittle solid and a poor conductor of heat and electricity could have an atomic number of
(1) 12        (3) 16
(2) 13        (4) 17
3 definition of a nonmetal,

not Cl because it is a gas

35 Based on Reference Table S, atoms of which of these elements have the strongest attraction for the electrons in a chemical bond?
(1) Al     (3) P
(2) Si     (4) S
4 Definition of Electronegativity

Use Table S

36 A sample of a compound contains 65.4 grams of zinc, 12.0 grams of carbon, and 48.0 grams of oxygen. What is the mole ratio of zinc to carbon
to oxygen in this compound?
(1) 1:1:2      (3) 1:4:6
(2) 1:1:3      (4) 5:1:4
2 divide each by the atomic mass

Zn  65.4/65.4=1

C 12/12=1

O 48/16=3

37 Which process would most effectively separate two liquids with different molecular polarities?
(1) filtration          (3) distillation
(2) fermentation   (4) conductivity
3 molecular polarities= different boiling points
38 Given the balanced equation:
AgNO3(aq) + NaCl(aq) ==> NaNO3(aq) + AgCl(s)
This reaction is classified as
(1) synthesis
(2) decomposition
(3) single replacement
(4) double replacement
4 DR
39 A solution contains 35 grams of KNO3 dissolved in 100 grams of water at 40C. How much more KNO3 would have to be added to make it a saturated solution?
(1) 29 g     (3) 12 g
(2) 24 g     (4) 4 g
1 Table G

find the difference between 35grams and the line at 40C

1 that is a gas

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

 
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