June 2014 Chemistry Regents #16-20
Highlight to reveal answers and explanations
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Questions | Answer | Links | Explanations |
| 16 Which change results in the formation of different substances? (1) burning of propane (2) melting of NaCl (s) (3) deposition of CO2(g) (4) solidification of water | 1 | link | phases changes do not result in a different substance. Chemical reactions do. |
| 17 Which substance can not be broken down by a chemical change? (1) ammonia (3) propanal (2) ethanol (4) zirconium | 4 | link | definition of an element zirconium is an element |
| 18 According to Table I, which equation represents a change resulting in the greatest quantity of energy released? (1 ) 2C(s) + 3H2 (g) à C2H6(g) (2) 2C(s) + 2 H2 (g) àC2H4(g) (3) N2 (g) + 3 H2 (g) à2NH3(g) (4) N2 (g) + O2(g) à2NO(g) | 3 | link | release is exothermic so DH is negative and has the largest number |
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| 19 Which clement is a liquid at STP? (1) bromine (3) francium (2) cesium (4) iodine | 1 | link | bromine is a liquid see the melting point on table S |
| 20 Which statement describes a reversible reaction at equilibrium? (1) The activation energy of the forward reaction must equal the activation energy of the reverse reaction. (2) The rate of the forward reaction must equal the rate of the reverse reaction. (3) The concentration of the reactants must equal the concentration of the products. (4) The potential energy of the reactants must equal the potential energy of the products. | 2 | link | at equilibrium concentrations are constant and rates are equal Con Con REqual |
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