Regents Chemistry Exam Explanations June 2004

Questions	Answer	Explanations
21 A catalyst increases the rate of a chemical reaction by (1) lowering the activation energy of the reaction (2) lowering the potential energy of the products (3) raising the temperature of the reactants (4) raising the concentration of the reactants	1	definition of a catalyst lowers activation energy
22 Which element must be present in an organic compound? (1) hydrogen (3) carbon (2) oxygen (4) nitrogen	3	carbon
23 Which compound is a saturated hydrocarbon?\ (1) hexane (3) hexanol (2) hexene (4) hexanal	1	saturated all single bonds alkanes C_nH_2n+2
	4	an ester is produced from an alcohol and acid --> Esterfication
25 Which of these compounds has chemical properties most similar to the chemical properties of ethanoic acid? (1) C₃H₇COOH (3) C₂H₅COOC₂H₅ (2) C₂H₅OH (4) C₂H₅OC₂H₅	1	the other acid
	1	Zn⁰ to Zn⁺²(SO₄^2-)
27 A voltaic cell spontaneously converts 1) electrical energy to chemical energy (2) chemical energy to electrical energy (3) electrical energy to nuclear energy (4) nuclear energy to electrical energy	2	Voltaic Spontaneous (A Battery) Electrolytic Nonspontaneous (Apply a current)
28 Which pair of formulas represents two compounds that are electrolytes? (1) HCl and CH₃OH (2) HCl and NaOH (3) C₅H₁₂ and CH₃OH (4) C₅H₁₂ and NaOH	2	Electrolytes Acids, bases and Salts **Never Alcohols CH₃OH
29 Hydrogen chloride, HCl, is classified as an Arrhenius acid because it produces (1) H⁺ ions in aqueous solution (2) Cl^– ions in aqueous solution (3) OH^–ions in aqueous solution (4) NH₄⁺ ions in aqueous solution	1	Acid H⁺ Base OH-
30 Which compound could serve as a reactant in a neutralization reaction? (1) NaCl (3) CH₃OH (2) KOH (4) CH₃CHO	2	Acid or Base