Unit 2
Which of the following solutions is the most concentrated?
0.5 liter of water with 50 grams of sugar
The molecules of a gas at room temperature move at about
1,500 km/hr.
When a hydronium ion concentration equals 1 × 10-13 moles per liter, what is the pH of the solution?
13
Compared to the mass of a hydrogen atom, the mass of an oxygen atom is
16 times greater.
How much energy is released upon the formation of the bonds within 1 mole of hydrazine, N2H4?
1715 kJ
How many shells are completely filled for the chlorine ion, Cl1- (Cl, atomic #17)?
3
Balance these equations:____ H2 (g) + ____ N2 (g) → ____ NH3 (g)
3, 1, 2
How many molecules of sucrose are in 0.5 L of a 1 molar solution of sucrose?
3.01 × 10^23 molecules of sucrose
Which set of coefficients balance the following chemical equation?
4, 8, 1, 6
How many electrons are in the outermost shell of phosphorus (P, atomic number 15)?
5
When a hydronium ion concentration equals 1 × 10-5 moles per liter, what is the pH of the solution?
5
How many shells are occupied by electrons in the gold atom (Au, atomic #79)?
6
Which has more atoms: 17.031 g of ammonia, NH3 (17.031 amu), or 72.922 g of hydrogen chloride, HCl (36.461 amu)?
72.922 g of HCl and 17.031 g of NH3 have about the same number of atoms.
Which has more atoms: 64.058 g of sulfur dioxide, SO2 (64.058 amu), or 72.922 g of hydrogen chloride, HCl (36.461 amu)
72.922 g of HCl has more atoms than 64.058 g of SO2
A pH of 7 signifies
A pH of 7 signifies
What is a heteroatom?
Any atom on an organic molecule other than hydrogen or carbon
At 10°C, which is more concentrated, a saturated solution of potassium nitrate, KNO3, or a saturated solution of sodium chloride? (See figure shown above.)
At 10°C a saturated solution of sodium chloride, NaCl, is more concentrated than a saturated solution of potassium nitrate, kNO3
At 10°C, which is more concentrated—a saturated solution of sodium nitrate, NaNO3, or a saturated solution of sodium chloride? (See figure shown above )
At 10°C a saturated solution of sodium nitrate, NaNO3, is more concentrated than a saturated solution of sodium chloride, NaCl.
If an atom has 43 electrons, 56 neutrons, and 43 protons, what is its approximate atomic mass? What is the name of this element?
Atomic mass, 99 amu; Technetium
Which color of light comes from the higher energy transition, red or blue?
Blue is a higher frequency and therefore corresponds to a higher energy level transition.
What is the boiling temperature of a single water molecule? Does this question make sense?
Boiling involves the separation of many molecules (plural). With only one molecule, the concept of boiling is meaningless.
In the following chemical reaction, which species is oxidized?Cl2 + 2 Br- → 2 Cl- + Br2
Br-
Under what conditions does an oxidizing agent donate electrons?
By definition, a chemical behaves as an oxidizing agent only when it accepts electrons.
Plastic wrap is made of nonpolar molecules and is able to stick well to polar surfaces, such as glass, by way of dipole/induced dipole molecular attractions. How is it that plastic wrap also sticks to itself so well?
By way of induced dipole-induced dipole molecular attractions.
Which of the following shows elements in order of increasing atomic size (Cl, atomic #17; K, atomic #19; Br, atomic #35; Rb, atomic #37)?
Cl<Br<K<Rb
How can you tell whether a sugar solution is saturated or not?
Cool the solution to see if there is a precipitate.
In the following chemical reaction, which species is oxidized?Fe + 2 H+ → Fe2+ + H2
Fe
Based on their relative positions in the periodic table, which might you expect to be a stronger oxidizing agent, chlorine or fluorine? Why?
Fluorine should behave as a stronger oxidizing agent because it has a greater effective nuclear charge in its outermost shell.
If gallium ions have a 3+ charge and a sulfur ions have a 2- charge, the compound gallium sulfide is
Ga2S3
Identify the acid or base behavior of each substance in these reactions:H3O+ + Cl- H2O + HCl
H3O+ acts as an acid, Cl- acts as a base, H2O acts an base, HCl acts as a acid
A base dissolved in water liberates
HO-
An inventor claims to have developed a new perfume that lasts a long time because it doesn't evaporate. Comment on this claim.
In order to smell something, the molecules must evaporate and reach your nose. If the new perfume doesn't evaporate, it will not have an odor.
How might you distinguish a sodium-vapor street lamp from a mercury-vapor street lamp?
Look at the street lamps through a spectroscope and match their spectral patterns to their respective atomic spectra.
Magnesium ions carry a 2+ charge, and chloride ions carry a 1- charge. What is the chemical formula for the ionic compound magnesium chloride?
MgCl2
Which of these statements is true?
Molecules are the smallest subdivision of matter that still retain chemical properties of a substance.
Which solute graphed in the figure shown above has a solubilty in water that does not markedly increase with increasing temperature?
NaCl
What is the relationship between the amu and the gram?
One gram is always greater than one amu.
List the following atoms in order of increasing atomic size: titanium, Ti; germanium, Ge; tin, Sn; phosphorus, P.
P<Ge<Sn<Ti
Some politicians take pride in maintaining a particular point of view. They think that a change of mind would be seen as a sign of weakness. How is a change of mind viewed differently in science?
Science deals with facts that are confirmed by experiments. A "change of mind" in science, therefore, is usually the result of new experimental evidence obtained from experiments.
Many solvents expand to occupy greater volumes with increasing temperature. What happens to the concentration of a solution made with such a solvent as its temperature is increased?
Since concentration depends on how much mass is dissolved in a given volume, as the volume increases, the concentration decreases.
Clorox is a laundry bleaching agent used to remove stains from white clothes. Suggest why the name begins with Clor- and ends with -ox.
The active ingredient contains chlorine atoms, which behave as strong oxidizing agents.
How is a physical change different from a chemical change?
The chemical identity of a substance is not altered during a physical change.
What is the hydroxide ion concentration in an aqueous solution when the hydronium ion concentration equals 1 × 10-10 moles per liter?
The concentration of hydroxide ions is 1 × 10-4 moles per liter.
What is the main difference between condensation polymers and addition polymers?
The condensation polymer has less atoms in it than the sum of the starting monomers because a small molecule is lost during condensation.
How does an atom's electronegativity relate to its ability to become oxidized?
The greater the electronegativity of an atom, the lower its ability to become oxidized.
The Arrhenius definition of a base is that which increases the concentration of hydroxide ions. How does ammonia, NH3, which is a base, satisfy the Arrhenius definition?
The hydrogen from water combines with the nitrogen from ammonia leaving behind the hydroxide ion.
What can you deduce about the activation energy of a reaction that takes billions of years to go to completion? How about a reaction that takes only fractions of a second?
The slow reaction must have a high activation energy while the fast reaction must have a low activation energy.
Why can't the elements of a compound be separated from one another by physical means?
Their atoms are too tightly bound to one another.
Why does a glowing splint of wood burn only slowly in air, but rapidly in a burst of flames when placed in pure oxygen?
There is a greater number of collisions between the wood and oxygen molecules.
Would you expect to find more dissolved oxygen in polar or tropical ocean waters? Why?
There would be more dissolved oxygen in the polar oceans because the solubility of oxygen in water decreases with increasing temperature.Oxygen has a low solubility in water because
What do chicken noodle soup and garden soil have in common?
They are both examples of heterogeneous mixtures.
One of the products of combustion is water. Why doesn't this water extinguish the combustion?
This water is in the gaseous phase and merely floats away from the fire.
Which is the smallest particle listed below?Which is the smallest particle listed below?
a quark
What exactly is a hydrogen bond?
a strong dipole-dipole attraction involving a hydrogen atom
What is the formula mass of sulfur dioxide, SO2?
about 64 amu
Control is exercised in a nuclear reactor by
absorbing excess neutrons with control rods.
The difference between an endothermic and exothermic reaction is that an endothermic reaction
absorbs energy but an exothermic reaction releases energy.
Which of the following substances is pure?
all of the above
The half-life of a radioactive substance is independent of
all of these
If a pair of helium nuclei are fused together, the result is
beryllium.
If an alpha particle and a beta particle have the same energy, which particle will penetrate the farthest in an object?
beta particle
Deuterium and tritium are both
both of these
If two protons are removed from an oxygen nucleus, the result is
carbon-14
When a nucleus emits a beta particle, its atomic number
changes, but its mass number remains constant.
Classify the following changes as physical or chemical. Even if you are incorrect in your assessment, you should be able to defend why you chose as you did. Wood burns to ashes; water begins to boil; grass grows; a rock is crushed to powder.
chemical; physical; chemical; physical
A salt bridge is needed in an electrochemical cell to
complete the electric circuit.
Classify the following bonds as ionic, covalent, or neither (O, atomic number 8; F, atomic number 9; Na, atomic number 11; Cl, atomic number 17; U, atomic number 92).O with F Ca with Cl Na with Na
covalent, ionic, neither
The components of a mixture are most efficiently separated from one another based upon their
differences in physical properties.
The proper name for the chemical compound N2O is
dinitrogen oxide.
The chemical properties of matter come mostly from its
electrons.
Once an alpha particle is outside the nucleus it is
electrostatically repelled.
The number of elements in a period is
equal to the electron capacity of the shells.
Which radiation has no electric charge associated with it?
gamma rays
If you filter sea water to remove all of the particles you would be left with a clear ________.
homogenous mixture called a solution
Strontium, Sr (number 38), is especially dangerous to humans because it tends to accumulate in calcium-dependent bone marrow tissues (calcium, Ca, number 20). This fact relates to the organization of the periodic table in that strontium and calcium are both
in group 2 of the periodic table.
A fuel cell differs from a battery in that
it can run indefinitely provided a continuous supply of fuel.
A weak acid is added to a concentrated solution of hydrochloric acid. Does the solution become more or less acidic?
less acidic, since the solution becomes more dilute with a less concentrated solution of hydronium ions being added to the solution
Compared to chemical changes, physical changes typically involve
less energy and reversibility.
Compared to the mass of a uranium nucleus before splitting, the pieces it splits into have
less mass.
As atoms get more massive they become smaller in size because
more mass means more protons, which act to pull electrons in closer to the nucleus.
What type of chemical bond would you expect between two neon atoms (Ne, atomic #10)?
none of the above
The atomic mass number of an element is the same as the number of its
nucleons.
During a chemical reaction
old atoms stick around merely switching partners.
How many molecules of water are there in 18 grams?
one mole
In an electrically neutral atom, the number of protons in the nucleus is balanced by an equal number of
orbital electrons.
When the hydronium ion concentration equals 1 mole per liter, what is the pH of the solution? Is the solution acidic or basic?
pH = 0, this is an acidic solution.
Would you use a physical model or a conceptual model to describe the following: the brain; the mind; the solar system; the beginning of the universe?
physical; conceptual; physical; conceptual
To say that an acid is strong in aqueous solution means the acid
produces a large concentration of hydronium ions.
The source of the earth's natural heat is
radioactive decay in the earth's core.
Oxygen has a low solubility in water because
the attraction between the nonpolar oxygen and polar water molecule is not strong enough to cause dissolving.
Ion-dipole attractions are stronger than dipole-dipole interactions because
the charge of an ion is much greater than the charge of a molecular dipole.
Water molecules are attracted to sodium chloride because
the dipoles of water are attracted to the ionic charges.
Salts are made of elements found on opposite ends of the periodic table because elements on
the far left tend to form positive ions while those on the right tend to form negative ions.
What is molarity?
the number of moles of solute per liter of solution
Compare to the atoms that make up the body of an elderly person, the atoms that make up the body of a newborn baby are
the same age.
What is the purpose of the salt bridge in a voltaic cell?
to allow for a balance of charge between the two chambers
What are the formula masses of water, H2O; propane, C3H6; and 2-propanol, C3H8O?
water: 18 amu. propene: 42 amu. 2-propanol: 60 amu
