General Biology 1 - BSC 1010C - Chapter 2: The Chemical
Context of Life Questions With Complete Solutions
Describe a reversible reaction. Correct Answers A reversible
reaction occurs when a chemical reaction can go both ways; it is
represented by an arrow pointing both ways. Example: 3 H2 +
N2 = 2 NH3.
From the atomic number or the position of an element in the
periodic table you should be able to determine its number of
valence electrons. For example, how many valence electrons
does hydrogen have? Oxygen? Correct Answers Hydrogen has
1 valence electron, while oxygen has 6 valence electrons.
How many grams of carbon equal one mole of carbon? How
many grams of NaCl equal a mole of NaCl? Correct Answers
Approximately 12 grams of carbon is equal to 1 mole. The
number of moles in a substance is determined using the
substance's molar mass, the number of grams in one mole of a
substance. 1 mole of NaCl (sodium chloride) is equal to
approximately 58 grams.
If Cl has 17 electrons, 17 protons, and 18 neutrons, what is its
mass number? Correct Answers Cl's atomic mass number
would be 35, based on the sum of its protons and neutrons.
If you came across the following notation in a textbook or
scientific journal, what information could you determine from
it? (23/11 Na) Correct Answers If you came across this
notation, you could determine the atomic mass, the number of
, protons, and the number of neutrons (by subtracting the atomic
number from the mass).
What are electron energy levels and electron shells? How many
electrons are the first, second, and third energy levels capable of
holding? How does the number of electrons on an atoms outer
shell affect the behavior of the atom/element? Correct Answers
An electron energy level is correlated with its average distance
from the nucleus and each level holds a certain number of
electrons, they exist whether electrons are there or not. Electron
shells are when electrons occupy these levels. The first energy
level can hold 2 electrons, and the second and third levels can
hold up to 8 electrons respectively. The number of electrons on
the outer shell (valence shell) affect the behavior of the atom
because if they are on the highest level, they have the most
energy.
What are isotopes? Stable isotopes? Radioactive isotopes?
Describe some examples of how scientists can utilize stable and
radioactive isotopes as tools. Correct Answers An isotope is one
of several atomic forms of an element, each with the same
number of protons but a different number of neutrons, thus
differing in atomic mass. Stable isotopes are when the nuclei do
not tend to lose subatomic particles. Radioactive isotopes are
unstable and the nucleus tends to decay spontaneously, giving
off particles and energy. Doctors can use radioactive isotopes for
treatment, specifically for cancer, and also as diagnostic tools
and tracers. Scientist also use them for dating fossils (especially
carbon-14) or to study the remains of living things.
Context of Life Questions With Complete Solutions
Describe a reversible reaction. Correct Answers A reversible
reaction occurs when a chemical reaction can go both ways; it is
represented by an arrow pointing both ways. Example: 3 H2 +
N2 = 2 NH3.
From the atomic number or the position of an element in the
periodic table you should be able to determine its number of
valence electrons. For example, how many valence electrons
does hydrogen have? Oxygen? Correct Answers Hydrogen has
1 valence electron, while oxygen has 6 valence electrons.
How many grams of carbon equal one mole of carbon? How
many grams of NaCl equal a mole of NaCl? Correct Answers
Approximately 12 grams of carbon is equal to 1 mole. The
number of moles in a substance is determined using the
substance's molar mass, the number of grams in one mole of a
substance. 1 mole of NaCl (sodium chloride) is equal to
approximately 58 grams.
If Cl has 17 electrons, 17 protons, and 18 neutrons, what is its
mass number? Correct Answers Cl's atomic mass number
would be 35, based on the sum of its protons and neutrons.
If you came across the following notation in a textbook or
scientific journal, what information could you determine from
it? (23/11 Na) Correct Answers If you came across this
notation, you could determine the atomic mass, the number of
, protons, and the number of neutrons (by subtracting the atomic
number from the mass).
What are electron energy levels and electron shells? How many
electrons are the first, second, and third energy levels capable of
holding? How does the number of electrons on an atoms outer
shell affect the behavior of the atom/element? Correct Answers
An electron energy level is correlated with its average distance
from the nucleus and each level holds a certain number of
electrons, they exist whether electrons are there or not. Electron
shells are when electrons occupy these levels. The first energy
level can hold 2 electrons, and the second and third levels can
hold up to 8 electrons respectively. The number of electrons on
the outer shell (valence shell) affect the behavior of the atom
because if they are on the highest level, they have the most
energy.
What are isotopes? Stable isotopes? Radioactive isotopes?
Describe some examples of how scientists can utilize stable and
radioactive isotopes as tools. Correct Answers An isotope is one
of several atomic forms of an element, each with the same
number of protons but a different number of neutrons, thus
differing in atomic mass. Stable isotopes are when the nuclei do
not tend to lose subatomic particles. Radioactive isotopes are
unstable and the nucleus tends to decay spontaneously, giving
off particles and energy. Doctors can use radioactive isotopes for
treatment, specifically for cancer, and also as diagnostic tools
and tracers. Scientist also use them for dating fossils (especially
carbon-14) or to study the remains of living things.
