June 2008 Chemistry Regents #41-50

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

 

Questions

Answer Explanations
41 A 1.0-gram sample of which element will uniformly fill a closed 2.0-liter container at STP?
(1) antimony    (3) tellurium
(2) sulfur          (4) xenon
4 will uniformly fill==>gas
42 Given the balanced equation representing a reaction:
C3H8(g) + 5O2(g)==>3CO2(g) + 4H2O(g)
What is the total number of moles of O2(g) required for the complete combustion of 1.5 moles of C3H8(g)?
(1) 0.30 mol   (3) 4.5 mol
(2) 1.5 mol     (4) 7.5 mol
4 set up a proportion

1.5/1  C3H8(g)  = x/5O2(g)

43 A sample of gas occupies a volume of 50.0 milliliters in a cylinder with a movable piston. The pressure of the sample is 0.90 atmosphere and the temperature is 298 K. What is the volume of the sample at STP?
(1) 41 mL      (3) 51 mL
(2) 49 mL      (4) 55 mL
1 PV/T =PV/T
44 Which solution has the lowest freezing point?
(1) 10. g of KI dissolved in 100. g of water
(2) 20. g of KI dissolved in 200. g of water
(3) 30. g of KI dissolved in 100. g of water
(4) 40. g of KI dissolved in 200. g of water
3 find the largest ratio of KI to water
45 Which 1-mole sample has the least entropy?
(1) Br2(s) at 266 K     (3) Br2(l) at 332 K
(2) Br2(l) at 266 K      (4) Br2(g) at 332 K
1 solid has least entropy
46 At 20.C, a 1.2-gram sample of Mg ribbon reacts rapidly with 10.0 milliliters of 1.0 M HCl(aq). Which change in conditions would have caused
the reaction to proceed more slowly?
(1) increasing the initial temperature to 25C
(2) decreasing the concentration of HCl(aq) to 0.1 M
(3) using 1.2 g of powdered Mg
(4) using 2.4 g of Mg ribbon
2 less surface area = slower reaction
47 Which general formula represents the compound CH3CH2CCH?
(1) CnHn       (3) CnH2n2
(2) CnH2n     (4) CnH2n+2
3 CH3CH2CCH==> C4H6

CnH2n2

 

48 Which compound dissolves in water to form an aqueous solution that can conduct an electric current?
(1) CCl4           (3) CH3COOH
(2) C2H5OH     (4) CH4
3 acids bases or salts

CH3COOH- acetic acid Table K

49 Given the equation representing a reaction at equilibrium:
NH3(g) + H2O(l) ==>NH4+(aq) + OH(aq)
The H+ acceptor for the forward reaction is
(1) H2O(l)    (3) NH4+(aq)
(2) NH3(g)   (4) OH(aq)
2 NH3(g)  ==>NH4+(aq)

it gained  H+

50 An original sample of K-40 has a mass of 25.00 grams. After 3.9 109 years, 3.125 grams of the original sample remains unchanged. What
is the half-life of K-40?
(1) 1.3 109 y     (3) 3.9 109 y
(2) 2.6 109 y     (4) 1.2 1010 y
1 25==>12.5==>6.25==>3.125  3 half lives

 3.9 109 years/ 3

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

 
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