August 2009 Chemistry Regents #41-50

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

Questions 51-55 Questions56-58 Questions 59-63 Question 64 Questions 65-67 Questions 68-72 Questions 73-76 Questions 77-79 Questions 80-81

 

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Questions

AnswerExplanations
1Line up the lines with the unknown
3synthesis reaction is chemical and

they have different properties

43 Which quantity of heat is equal to 200. joules?
(1) 20.0 kJ     (3) 0.200 kJ
(2) 2.00 kJ     (4) 0.0200 kJ		3divide by 1000
4indirect
45 The entropy of a sample of H2O increases as the sample changes from a
(1) gas to a liquid    (3) liquid to a gas
(2) gas to a solid     (4) liquid to a solid		3SLG problem liquid to gas is more random
46 Ethanol and dimethyl ether have different chemical and physical properties because they have different
(1) functional groups
(2) molecular masses
(3) numbers of covalent bonds
(4) percent compositions by mass		1alcohol vs. ether Table R
1unsaturated not all single bonds

hydrocarbon=> hydrogen and carbon only

48 What is the oxidation state of nitrogen in the
compound NH4Br?
(1) –1         (3) –3
(2) +2        (4) +4		3N=-3

H=+1 x 4

Br=-1

49 A student completes a titration by adding 12.0 milliliters of NaOH(aq) of unknown concentration to 16.0 milliliters of 0.15 M HCl(aq).
What is the molar concentration of the NaOH(aq)?
(1) 0.11 M     (3) 1.1 M
(2) 0.20 M     (4) 5.0 M		2MV=MV

M(12.0mL)=0.15M(16.0mL)

50 What is the half-life of a radioisotope if 25.0 grams of an original 200.-gram sample of the isotope remains unchanged after 11.46 days?
(1) 2.87 d     (3) 11.46 d
(2) 3.82 d     (4) 34.38 d		2200->100->50->25  4 half lives

11.46d  / 4 =3.82d

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

Questions 51-55 Questions56-58 Questions 59-63 Question 64 Questions 65-67 Questions 68-72 Questions 73-76 Questions 77-79 Questions 80-81

 
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