Practice Quiz

MCAS Biology Practice - Question List

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191. Which of the following statements explains why oxygen is classified asa pure substance and air is classifiedas a mixture?
  1. Oxygen is more reactive than air.
  2. Oxygen has a higher density than air.
  3. Oxygen undergoes phase changes, whereas air is always a gas.
  4. Oxygen contains only one substance, but air contains several substances.
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192. The pH of milk is 6.4. Based on this information, which of the following statements best describes milk?
  1. It is very basic.
  2. It is very acidic.
  3. It is slightly basic.
  4. It is slightly acidic.
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193. 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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194. 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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195. 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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