August 2006 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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AnswerExplanations
31 What is the mass number of an atom that has six protons, six electrons, and eight neutrons?
(1) 6     (3) 14
(2) 12   (4) 20
36 protons =atomic # 6
2mass# of 27= 13p+ and 14no
4an electron mass is approximately 1/1836 of a proton, so the proton is about 2000x more massive
34 Based on electronegativity values, which type of elements tends to have the greatest attraction for electrons in a bond?
(1) metals        (3) nonmetals
(2) metalloids   (4) noble gases
3fluorine is the greatest, it is a nonmetal
35 Which list of elements from Group 2 on the Periodic Table is arranged in order of increasing  atomic radius?
(1) Be, Mg, Ca      (3) Ba, Ra, Sr
(2) Ca, Mg, Be      (4) Sr, Ra, Ba
1Table S has the values, put them in order
36 Which half-reaction shows conservation of charge?
(1) Cu + e- --> Cu+        (3) Cu+ --> Cu + e-
(2) Cu2+ + 2e- --> Cu    (4) Cu2+ -->Cu + 2e-
2The total charge on the left must equal the total charge on the right
1plug in mass of MG and divide by total x100%
38 Given the balanced equation:
CaCO3(s) + 2HCl(aq) -->CaCl2(aq) + H2O(l) + CO2(g)
What is the total number of moles of CO2 formed when 20. moles of HCl is completely consumed?
(1) 5.0 mol     (3) 20. mol
(2) 10. mol     (4) 40. mol
2set up a proportion

20/2 =x/1

39 What amount of heat is required to completely melt a 29.95-gram sample of H2O(s) at 0C?
(1) 334 J      (3) 1.00 103 J
(2) 2260 J    (4) 1.00 104 J
4melt (fusion)

q=mHf= 29.95 x 334

4elements are not attached

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