January 2007 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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31 When the elements in Group 1 are considered in order from top to bottom, each successive element at standard pressure has
(1) a higher melting point and a higher boiling point
(2) a higher melting point and a lower boiling point
(3) a lower melting point and a higher boiling point
(4) a lower melting point and a lower boiling point		4use table S
32 Which isotopic notation identifies a metalloid that is matched with the corresponding number of protons in each of its atoms?
(1) 24Mg and 12 protons
(2) 28Si and 14 protons
(3) 75As and 75 protons
(4) 80Br and 80 protons		2see table N

atomic # is the number of protons

33 At STP, which list of elements contains a solid, a liquid, and a gas?
(1) Hf, Hg, He     (3) Ba, Br2, B
(2) Cr, Cl2, C      (4) Se, Sn, Sr		1Hg and Br2 are liquids

He and Cl2 are gases

the rest are solids

34 Element X reacts with iron to form two different compounds with the formulas FeX and Fe2X3.
To which group on the Periodic Table does element X belong?
(1) Group 8    (3) Group 13
(2) Group 2    (4) Group 16		4X has a 2- charge

so group 16

35 The molar mass of Ba(OH)2 is
(1) 154.3 g   (3) 171.3 g
(2) 155.3 g   (4) 308.6 g		3Ba 137.3 + O (2 x 16.0) + H (2 x 1.0)=155.3
36 Given the balanced equation representing a reaction:
4NH3 + 5O2 ==>4NO + 6H2O
What is the minimum number of moles of O2 that are needed to completely react with 16 moles of NH3?
(1) 16 mol     (3) 64 mol
(2) 20. mol    (4) 80. mol		2set up a proportion

16/4 = x/5

1that is hydroxide

oxygen gets an octet  H gets a duet of electrons

38 A 10.0-gram sample of which element has the smallest volume at STP?
(1) aluminum     (3) titanium
(2) magnesium  (4) zinc		4the most dense, table S
39 At which temperature would atoms of a He(g) sample have the greatest average kinetic energy?
(1) 25°C     (3) 273 K
(2) 37°C     (4) 298 K		2average KE is temp

37C is 310K

2use table G, the point will be on the line

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