January 2011 Chemistry Regents #11-20
Highlight to reveal answers and explanations
Questions | Answer | Explanations |
| 11 What is the total number of electron pairs shared between the two atoms in an O2 molecule? (1) 1 (3) 6 (2) 2 (4) 4 | 2 | oxygen has a double bond so 2pairs of electrons |
| 12 When an atom of lithium loses an electron, the atom becomes a (1) negative ion with a radius smaller than the radius of the atom (2) negative ion with a radius larger than the radius of the atom (3) positive ion with a radius smaller than the radius of the atom (4) positive ion with a radius larger than the radius of the atom | 3 | losing electrons makes it positive and smaller |
| 13 Given the balanced equation representing a reaction: 2NaCl → 2Na + Cl2 To break the bonds in NaCl, the reactant must (1) absorb energy (3) destroy energy (2) create energy (4) release energy | 1 | breaking bonds requires energy |
| 14 A molecular compound is formed when a chemical reaction occurs between atoms of (1) chlorine and sodium (2) chlorine and yttrium (3) oxygen and hydrogen (4) oxygen and magnesium | 3 | molecular is covalent two nonmetals |
| 15 Which substance can not be broken down by chemical means? (1) ammonia (3) methane (2) antimony (4) water | 2 | definition of an element |
| 16 Which two physical properties allow a mixture to be separated by chromatography? (1) hardness and boiling point (2) density and specific heat capacity (3) malleability and thermal conductivity (4) solubility and molecular polarity | 4 | chromatography= solubility and polarity |
| 17 The solubility of KCl(s) in water depends on the (1) pressure on the solution (2) rate of stirring (3) size of the KCl sample (4) temperature of the water | 4 | solubility of a solid depends temperature |
| 18 Which sample of water contains particles having the highest average kinetic energy? (1) 25 mL of water at 95°C (2) 45 mL of water at 75°C (3) 75 mL of water at 75°C (4) 95 mL of water at 25°C | 1 | highest average kinetic energy=highest temperature |
| 19 Under which conditions of temperature and pressure does carbon dioxide gas behave most like an ideal gas? (1) low temperature and low pressure (2) low temperature and high pressure (3) high temperature and low pressure (4) high temperature and high pressure | 3 | ideal gas is like an ideal vacation high temperature and low pressure |
| 20 Which process results in a chemical change? (1) tearing tin foil (2) melting an iron bar (3) crushing an aluminum can (4) burning magnesium ribbon | 4 | chemical changes are reactions |