Practice Quiz

MCAS Chemistry Exam Practice - Question List

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26. Formaldehyde in solution is used as a preservative. It has a melting point of -92°C. When the temperature of a sample of formaldehyde rises from -93°C to -91°C, which of the following occurs?
  1. The molecules move more freely.
  2. The molecules lose electrical charge.
  3. The molecules break apart into atoms.
  4. The molecules become fixed in a crystal structure.
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27. Which of the following solutions has the highest concentration of solute?
  1. 1.0 mol solute in 200 mL solvent
  2. 2.0 mol solute in 500 mL solvent
  3. 3.0 mol solute in 1 L solvent
  4. 4.0 mol solute in 1.5 L solvent
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28. A hiker carries drinking water in a cloth-covered, metal container called a canteen. During the summer, the hiker wets the cloth covering so that the water in the canteen stays cool. Which of the following statements explains why a wet covering keeps the water cool?
  1. A wet covering transfers coolness to the water in the canteen.
  2. A wet covering insulates the canteen better than a dry covering.
  3. Evaporation of water from the covering transfers heat away from the canteen.
  4. Condensation of water from the covering transfers heat away from the canteen.
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29. Which of the following statements explains what happens to the gas inside a balloon as the external pressure on the balloon decreases and the temperature stays constant?
  1. The volume increases.
  2. The volume decreases.
  3. The molecular speed increases.
  4. The molecular speed decreases.
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30. Which of the following statements best explains why ice floats on water?
  1. Water has a higher specific heat than ice.
  2. Ice has the same molecular mass as water.
  3. Heat is absorbed when water changes from the solid state to the liquid state
  4. Hydrogen bonding causes water to be less dense in the solid state than in the liquid state.
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