Regents Chemistry Exam Explanations January 2003

Questions	Answer	Explanations
31 According to Table N, which radioactive isotope is best for determining the actual age of Earth? (1) 238 U (3)60 Co (2) 90 Sr (4) 14 C	1	the earth is old the one with the largest halflife
32 Given the following solutions: Solution A: pH of 10 Solution B: pH of 7 Solution C: pH of 5 Which list has the solutions placed in order of increasing H + concentration? (1) A, B, C (3) C, A, B (2) B, A, C (4) C, B, A	1	H= is referring to acidity high pH is a base low pH is acidic
33 Which statement explains why nuclear waste materials may pose a problem? (1) They frequently have short half-lives and remain radioactive for brief periods of time. (2) They frequently have short half-lives and remain radioactive for extended periods of time. (3) They frequently have long half-lives and remain radioactive for brief periods of time. (4) They frequently have long half-lives and remain radioactive for extended periods of time.	4	it is dangerous if it doesn't go away
34 A compound whose water solution conducts electricity and turns phenolphthalein pink is (1) HCl (3) NaOH (2) HC₂H₃O₂ (4) CH₃OH	3	pink is a base
35 Which of the following solids has the highest melting point? (1) H₂O(s) (3) SO₂(s) (2) Na₂O(s) (4) CO₂(s)	2	Ionic high melting point
36 Hydrogen has three isotopes with mass numbers of 1, 2, and 3 and has an average atomic mass of 1.00794 amu. This information indicates that (1) equal numbers of each isotope are present (2) more isotopes have an atomic mass of 2 or 3 than of 1 (3) more isotopes have an atomic mass of 1 than of 2 or 3 (4) isotopes have only an atomic mass of 1	3	atomic mass is a weighed average and is closest to the most abundant isotope
37 Which list of elements contains two metalloids? (1) Si, Ge, Po, Pb (3) Si, P, S, Cl (2) As, Bi, Br, Kr (4) Po, Sb, I, Xe	1	Si Ge
	1	enery is a product so it is exothermic
39 A chemist performs the same tests on two homogeneous white crystalline solids, A and B. The results are shown in the table below. The results of these tests suggest that (1) both solids contain only ionic bonds (2) both solids contain only covalent bonds (3) solid A contains only covalent bonds and solid B contains only ionic bonds (4) solid A contains only ionic bonds and solid B contains only covalent bonds	4	Solid A properties of an ionic compound Solid B is the properties of a covalent molecule
40 Solubility data for four different salts in water at 60°C are shown in the table below. Which salt is most soluble at 60°C? (1) A (3) C (2) B (4) D	4	divide D =0.50g/mL