| Questions | Answers | Explanations |
11 Which grouping of the three phases of bromine is listed in order from left to right for increasing distance between bromine molecules?(1) gas, liquid, solid (3) solid, gas, liquid (2) liquid, solid, gas (4) solid, liquid, gas | 4 | Solid is the most compact phase, then liquid and finally gas |
12 Which statement concerning elements is true? (1) Different elements must have different numbers of isotopes.(2) Different elements must have different numbers of neutrons.(3) All atoms of a given element must have the same mass number.(4) All atoms of a given element must have the same atomic number. | 4 | All atoms of an element have the same atomic number (protons) |
13 At room temperature, the solubility of which solute in water would be most affected by a change in pressure?(1) methanol (3) carbon dioxide (2) sugar (4) sodium nitrate | 3 | Pressure only effects gases |
14 Based on Reference Table I, which change occurs when pellets of solid NaOH are added to water and stirred?(1) The water temperature increases as chemical energy is converted to heat energy.(2) The water temperature increases as heat energy is stored as chemical energy.(3) The water temperature decreases as chemical energy is converted to heat energy.(4) The water temperature decreases as heat energy is stored as chemical energy. | 1 | since delta H is negative, the dissolving process is exothermic and the temperature of the water increases |
15 The concept of an ideal gas is used to explain (1) the mass of a gas sample (2) the behavior of a gas sample (3) why some gases are monatomic (4) why some gases are diatomic | 2 | how gases behave |
16 Molecules in a sample of NH 3(l) are held closely together by intermolecular forces(1) existing between ions (2) existing between electrons (3) caused by different numbers of neutrons (4) caused by unequal charge distribution | 4 | intermolecular forces are between molecules and caused by the unequal distribution of charge in the molecules |
17 Which process represents a chemical change? (1) melting of ice (2) corrosion of copper (3) evaporation of water (4) crystallization of sugar | 2 | chemical changes, look for the reaction physical is phase changes |
18 At STP, which 4.0-gram zinc sample will react fastest with dilute hydrochloric acid?(1) lump (3) powdered (2) bar (4) sheet metal | 3 | surface area, more surface more places to react |
19 Which information about a chemical reaction is provided by a potential energy diagram? (1) the oxidation states of the reactants and products(2) the average kinetic energy of the reactants and products(3) the change in solubility of the reacting substances(4) the energy released or absorbed during the reaction | 4 | PE diagrams provide a way to show energy changes in a reaction |
20 A catalyst works by (1) increasing the potential energy of the reactants (2) increasing the energy released during a reaction (3) decreasing the potential energy of the products (4) decreasing the activation energy required for a reaction | 4 | definition- lowers activation energy |
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