Test 8
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Which of the following has the greatest mass?
1 mole of Pb
Which is greater: 1.01 amu of hydrogen or 1.01 grams of hydrogen?
1.01 grams of hydrogen is greater than 1.01 amu of hydrogen.
What is the mass of an oxygen atom, O, in atomic mass units?
16 amu
What is the mass of a water molecule in atomic mass units?
18 AMU
How many valence electrons does boron (B, atomic no. = 5) have?
3
How many valence electrons does gallium (Ga, atomic no. = 31) have?
3
What is the formula mass of a molecule of carbon dioxide?
44 amu
How many valence electrons does bromine (Br, atomic no. = 35) have?
7
What is the relationship between the hydroxide ion and a water molecule?
A hydroxide ion is a water molecule minus a hydrogen nucleus.
Water is formed from the reaction of an acid and a base. Why is it not classified as a salt?
A salt is an ionic compound, whereas water is a covalent compound.
Which of the following statements about strong or weak bases is true?
A strong base will readily accept protons from even weak acids.
Which of the following statements about strong AND weak acids is not true?
A weak acid is as corrosive as a strong acid.
Which of the following statements about strong OR weak acids is true?
A weak acid will react with a strong base.
Which of the following statements about strong and weak bases is not true?
A weak base will not react with a strong acid.
Which of the following elements will most likely not form an ion at all?
Ar
Why does an atom with many valence electrons tend to gain electrons rather than lose any?
Atoms with many valence electrons tend to have relatively strong forces of attraction between the valence electrons and the nucleus. This makes it easy for them to gain additional electrons.
What would be the best explanation for the fact that most natural water has a pH of about 5.6?
Carbon dioxide reacts with water to form an acid.
Which of the following elements will most likely form an ion with a negative 1 charge?
Cl
How do the electron-dot structures of elements in the same group in the periodic table compare with one another?
Elements of the same group have the same number of valence electrons.
Which of the following statements accurately describes the action of ozone?
It absorbs UV radiation and undergoes fragmentation.
What happens to the pH of soda water as it loses its carbonation?
It increases as it loses the carbon dioxide molecules which form the carbonic acid in the soda.
What is a chemical equation?
It is a shorthand notation for illustrating a chemical reaction.
Why do we use the pH scale to indicate the acidity of a solution rather than simply stating the concentration of hydronium ions?
It is more convenient, since the concentration of hydronium ions is so small.
What is the valence shell?
It is the outermost shell of electrons in an atom.
What is a reaction rate?
It is the speed at which reactants are consumed or product is formed.
How does a catalyst increase the rate of a reaction?
It lowers the activation energy.
Why is it important for a chemist to know the relative masses of atoms?
It provides information about how many atoms two samples have relative to each other.
Why is it better to recycle metals than to mine more?
It takes far less energy to recycle.
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.
Why are ores so valuable?
Metals can be efficiently extracted from them.
Which of the following elements has two valence electrons?
Mg
Which of the following elements will most likely form an ion with a positive 2 charge?
Mg
Which of the following elements will most likely form an ion with a positive 1 charge?
Na
If a neutral atom gains two electrons, what is the electrical charge of the atom?
Negative 2
Is it possible to have a macroscopic sample of oxygen that has a mass of 14 atomic mass units?
No, this is less than than the mass of a single oxygen atom.
Which of the following statements is not true about a neutralization reaction?
None of these are true.
Which of the following elements has six valence electrons?
O
Which of the following statements about ozone is true?
Ozone in the stratosphere is beneficial.
Which of the following elements will most likely form an ion with a negative 2 charge?
S
An acid and a base react to form a salt, which consists of positive and negative ions. Which forms the positive ions: the acid or the base? Which forms the negative ions?
The acid forms the negative ion, the base forms the positive ion.
Suggest why people once washed their hands with ashes.
The ashes act as a base and reacts with skin oils to produce solutions of soap.
How is Avogadro's number related to the numbers on the periodic table?
The atomic mass listed is the mass of Avogadro's number's worth of atoms.
A friend argues that if mass were really conserved he would never need to refill his gas tank. What explanation do you offer your friend?
The atoms (mass) of gasoline are converted into exhaust fumes.
What happens to the corrosive properties of an acid and a base after they neutralize each other? Why?
The corrosive properties are neutralized because the acid and base no longer exist.
Why might increasing the temperature alter the rate of a chemical reaction?
The molecules will have a higher kinetic energy and bump into one another harder.
How is the number of unpaired valence electrons in an atom related to the number of bonds that the atom can form?
The number of unpaired valence electrons in an atom is the SAME as the number of bonds that the atom can form.
What happens to the pH of an acidic solution as water is added?
The pH will increase as the solution becomes more dilute.
What best describes what happens when an acid such as HCl is mixed with water?
The proton chemically bonded to the chlorine is transferred to a water molecule and forms a chloride ion and a hydronium 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 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.
The yeast in bread dough feeds on sugar to produce carbon dioxide. Why does the dough rise faster in a warmer area?
There is a greater number of effective collisions among reacting molecules.
Why is it so easy for a magnesium atom to lose two electrons?
These two electrons are well shielded from the nuclear charge.
Which of the following does not describe ionic compounds?
They have a tendency to melt easily.
Why might increasing the concentration of a set of reactants increase the rate of reaction?
You have increased the chances that any two reactant molecules will collide and react.
Which of the following solutions is the most acidic?
a solution with a pH is 7
What is the formula mass of sulfur dioxide, sulfur dioxide?
about 64 amu
What is the main characteristic of a strong acid?
all of these
What is the main characteristic of a strong base?
all of these
Why is heat often added to chemical reactions performed in the laboratory?
all of these
What is a base?
anything that accepts a hydrogen ion
What is an acid?
anything that donates hydrogen ions
An atom loses an electron to another atom. Is this an example of a physical or chemical change?
chemical change involving the formation of ions
Is the synthesis of ozone from oxygen an example of an exothermic or endothermic reaction?
endothermic because ultraviolet light is absorbed during its formation
As the pH increases, the hydroxide ion concentration
gets larger
As the hydronium ion concentration increases, the pH
goes down
Many of the macroscopic properties of a compound depend on
how the atoms of the molecules are held together.
The concept of a chemical bond is
how two or more atoms are held together
Which of the following best describes ionic bonding?
one atom giving up some of its electrons to another atom
A refrigerator delays the spoilage of food by
slowing down the rate of chemical reactions within microorganisms
What is activation energy?
the minimum amount of energy to break the bonds in reactants
The neon atom tends not to gain any additional electrons because
there is no more room available in its outermost occupied shell.
What is one role of unpaired valance electrons?
they take part in the formation of different types of bonds
Sodium hydroxide, NaOH, is a strong base, which means that it readily accepts hydrogen ions. What products are formed when sodium hydroxide accepts a hydrogen ion from a water molecule?
water and sodium hydroxide
What is a chemical reaction?
when one or more new compounds are formed by rearranging atoms