Practice Quiz

MCAS Chemistry Exam Practice - Question List

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16. A hospital buys a compound that contains an isotope of barium. Several months later, most of the barium has changed to the element lanthanum. Which of the following is responsible for this change?
  1. exposure to air
  2. radioactive decay
  3. reactions with the container wall
  4. absorption of moisture from the air
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17. A student made a homogeneous mixture of water and salt. Which of the following statements applies to this homogeneous mixture?
  1. This mixture is a solution.
  2. This mixture is a pure substance.
  3. The salt is not evenly distributed throughout this mixture.
  4. The salt chemically combines with the water in this mixture.
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18. Which of the following statements best explains why elements in the same family of the periodic table have similar bonding properties?
  1. The elements have similar atomic sizes.
  2. The elements have similar atomic masses.
  3. The elements have similar numbers of protons.
  4. The elements have similar valence electron configurations.
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19. Which of the following statements describes all exothermic reactions?
  1. Exothermic reactions form gases.
  2. Exothermic reactions require a catalyst.
  3. The energy of the reactants is lower than the energy of the products.
  4. The energy of the reactants is higher than the energy of the products.
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20. Which of the following statements best explains why potassium (K) reacts easily with bromine (Br)?
  1. Potassium and bromine both have valence electrons in the fourth energy level.
  2. Potassium and bromine have the same number of electrons in their highest energy levels.
  3. Potassium has one electron in its highest energy level, and bromine needs one electron to complete its highest energy level.
  4. Potassium needs one electron to complete its highest energy level, and bromine has an extra electron in its highest energy level.
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