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NPCIL Trainee The Chemical Foundation of Life — practice questions

Explore 19 free The Chemical Foundation of Life questions in NPCIL Trainee Biology. Open each question or exercise to read its content, reference answers and available explanation.

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The Chemical Foundation of Life questions and exercises with answers

Showing questions 1–19 of 19.

In chemistry and biology, "matter" is defined as:Read the answer and worked solution →There are 118 known chemical elements. How many of these occur naturally?Read the answer and worked solution →Isotopes of the same element are atoms that differ only in their number of:Read the answer and worked solution →The time required for half of a radioactive isotope's original concentration to decay to a more stable form is called its:Read the answer and worked solution →The octet rule states that, with the exception of the innermost shell, atoms are most energetically stable when their valence shell contains:Read the answer and worked solution →When an atom gains electrons to become a negatively charged ion, its elemental name is altered to end in which suffix (e.g. chlorine becomes chloride)?Read the answer and worked solution →The amount of energy required to change one gram of a liquid substance into a gas is called its:Read the answer and worked solution →The attraction between water molecules to each other, arising from hydrogen bonding, is called:Read the answer and worked solution →An acid is a substance that, when placed in solution, does what to the hydrogen ion concentration?Read the answer and worked solution →Hydrochloric acid (HCl) is described as a strong acid because, in water, it:Read the answer and worked solution →The buffer system that helps maintain a stable pH in human blood mainly involves carbonic acid, bicarbonate ion, and which gas?Read the answer and worked solution →The pH scale is an inverse logarithmic scale. What is its full range?Read the answer and worked solution →A carbon atom, with an atomic number of six, typically forms how many covalent bonds in order to satisfy the octet rule?Read the answer and worked solution →Sort the subatomic particlesRead the answer and worked solution →Count the particlesRead the answer and worked solution →Match each term to its meaningRead the answer and worked solution →Which half-life is longer?Read the answer and worked solution →Complete the shell rulesRead the answer and worked solution →True or false: atoms and isotopesRead the answer and worked solution →

Worked practice questions

In chemistry and biology, "matter" is defined as:

  1. anything that occupies space and has mass
  2. only living substances
  3. any substance carrying an electric charge
  4. any gas at room temperature
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Correct answer: A. anything that occupies space and has mass

1. The stem asks for the most fundamental definition used at the start of this topic. 2. The text states: "Matter is any substance that occupies space and has mass." 3. This definition applies equally to living and non-living material, to charged and uncharged substances, and to solids, liquids, and gases alike. 4. So matter is defined simply as anything occupying space and having mass -- not restricted to living things, charge, or a particular state. _Source: OpenStax Biology Ch 2 "The Chemical Foundation of Life", p.33 §2.1 | Atoms, Isotopes, Ions, and Molecules: The Building Blocks_

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There are 118 known chemical elements. How many of these occur naturally?

  1. 100
  2. 92
  3. 108
  4. All 118
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Correct answer: B. 92

1. The text distinguishes between the total number of known elements and the subset that occurs in nature. 2. It states: "There are 118 elements, but only 92 occur naturally. The remaining elements are synthesized in laboratories and are unstable." 3. So the elements beyond the 92nd are all laboratory-synthesized and unstable, not naturally occurring. 4. This means the correct count of naturally occurring elements is 92, not 100, 108, or all 118. _Source: OpenStax Biology Ch 2 "The Chemical Foundation of Life", p.33 §2.1 | Atoms, Isotopes, Ions, and Molecules: The Building Blocks_

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Isotopes of the same element are atoms that differ only in their number of:

  1. protons
  2. electrons
  3. neutrons
  4. valence shells
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Correct answer: C. neutrons

1. An element is defined by a fixed number of protons, so that number cannot vary between isotopes of the same element. 2. The text states: "isotopes, which are different forms of the same atom that vary only in the number of neutrons they possess." 3. Protons stay fixed (that is what makes them the same element), and while electron count can change in ions, isotopes are specifically about neutral atoms differing in neutrons. 4. So isotopes of an element differ only in their neutron count. _Source: OpenStax Biology Ch 2 "The Chemical Foundation of Life", p.34 §2.1 | Atoms, Isotopes, Ions, and Molecules: The Building Blocks_

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