August 2002 Chemistry Regents #11-20
Highlight to reveal answers and explanations
Questions 1-10 Questions 11-20 Questions 21-30 Questions 31-40 Questions 41-50 |
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Questions | Answer | Explanations |
| 11 Which formula represents an ionic compound? (1) NaCl (3) HCl (2) N2O (4) H2O | 1 | metal and nonmetal, far apart on the PT |
| 12 Which species does not have a noble gas electron configuration? (1) Na+ (3) Ar (2) Mg2+ (4) S | 4 | group 18, + charge has lost electrons |
| 13 Which statement correctly describes a chemical reaction at equilibrium? (1) The concentrations of the products and reactants are equal. (2) The concentrations of the products and reactants are constant. (3) The rate of the forward reaction is less than the rate of the reverse reaction. (4) The rate of the forward reaction is greater than the rate of the reverse reaction. | 2 | Equilibrium Question- concentrations stay constant or rates are equal |
| 14 Given the reaction: CH4(g) + 2 O2(g) -->2 H2O(g) + CO2(g) What is the overall result when CH4(g) burns according to this reaction? (1) Energy is absorbed and DH is negative. (2) Energy is absorbed and DH is positive. (3) Energy is released and DH is negative. (4) Energy is released and DH is positive. | 3 | Burns exothermic, DH =neg., energy released or look up on table I |
| 15 A hydrated salt is a solid that includes water molecules within its crystal structure. A student heated a 9.10-gram sample of a hydrated salt to a constant mass of 5.41 grams. What percent by mass of water did the salt contain? (1) 3.69% (3) 40.5% (2) 16.8% (4) 59.5% | 3 | water= 9.10-5.41= 3.69g H2O (3.69/9.10) x 100= 40.5% |
| 16 Which statement correctly describes a sample of gas confined in a sealed container? (1) It always has a definite volume, and it takes the shape of the container. (2) It takes the shape and the volume of any container in which it is confined. (3) It has a crystalline structure. (4) It consists of particles arranged in a regular geometric pattern. | 2 | definition of a gas |
| 17 Which molecule contains a triple covalent bond? (1) H2 (3) O2 (2) N2 (4) Cl2 | 2 | N2 N=5 valance electrons, bonds 3 times always on the regents |
| 18 The solid and liquid phases of water can exist in a state of equilibrium at 1 atmosphere of pressure and a temperature of (1) 0°C (3) 273°C (2) 100°C (4) 373°C | 1 | melting point of water (also freezing pt) see #5 |
| 19 Which compound is an alcohol? (1) propanal (3) butane (2) ethyne (4) methanol | 4 | ends with -ol |
| 20 In which reaction is soap a product? (1) addition (3) saponification (2) substitution (4) polymerization | 3 | saponification -->soaponification |
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