June 2007 Chemistry Regents #31-40

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

Questions	Answer	Explanations
31 Which electron configuration could represent a strontium atom in an excited state? (1) 2–8–18–7–1         (3) 2–8–18–8–1 (2) 2–8–18–7–3         (4) 2–8–18–8–2	2	38 electrons NOT 2-8-18-8-2
	1	Use Table S or know the falling down snowman trick
	2	57-26= neutrons
34 At STP, which element is brittle and not a conductor of electricity? (1) S      (3) Na (2) K     (4) Ar	1	nonmetal properties
35 What is the total number of electrons in a Mg2+ ion? (1) 10 (3) 14 (2) 12 (4) 24	1	Mg atom 12 electrons Mg2+ ion has lost 2 so it has 10 electrons
36 Which formula represents lead(II) chromate? (1) PbCrO4        (3) Pb2CrO4 (2) Pb(CrO4)2    (4) Pb2(CrO4)3	1	Pb2+ CrO42- 1:1 ratio
37 Compared to an electron in the first electron shell of an atom, an electron in the third shell of the same atom has (1) less mass     (3) more mass (2) less energy   (4) more energy	4	higher energy level more energy...duh
38 Which pair consists of a molecular formula and its corresponding empirical formula? (1) C2H2 and CH3CH3 (3) P4O10 and P2O5 (2) C6H6 and C2H2 (4) SO2 and SO3	3	empirical is a reduced form of the molecular
	4	Must be 2 different elements attached all compounds must be the same
	3	Mean Question 5 protons is Boron electron configuration is 2-3 3 dots

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

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