What is the activation energy?
the energy difference between the reactants and the products
the amount of energy required to activate a phase change
the amount of energy required to separate reactants from the products
the minimum amount of energy in order to transform into product molecules
the hill
Why might increasing the concentration of a set of reactants increase the rate of reaction?
You have increased the ratio of reactants to products.
The rate of reaction depends only on the mass of the atoms and therefore increases as you increase the mass of the reactants.
The concentration of reactants is unrelated to the rate of reaction.
You have increased the chances that any two reactant molecules will collide and react.
none of the above
What is the formula mass of a molecule of C6H12O6?
180 amu
24 amu
168 amu
29 amu
If it takes 200 golf balls to equal the mass of four bowling balls, what is the relative mass of bowling balls to golf balls?
20 times
1/20
100 times
6.022 × 1023
1/50
Given the following generic chemical reaction, which is the product?
X → Y
→ is the product.
X is the product.
Y is the product.
Both X and Y are the products.
Both X and Y are the reactants.
Which of the following reaction energies is the most endothermic?
-540 kJ/mole
540 kJ/mole
125 kj/mole
-125 kJ/mole
not enough information given
Use the bond energies below to determine whether the following reaction is exothermic or endothermic:
H2 + Cl2 → 2 HCl
H-H (bond energy: 436 kJ/mol) Cl-Cl (bond energy: 243 kJ/mol) H-Cl (bond energy: 431 kJ/mol)
Exothermic with more than 50 kJ of energy released.
Endothermic with more than 50 kJ of energy absorbed.
Endothermic with less than 50 kJ of energy absorbed.
Exothermic with less than 50 kJ of energy released.
What is an exothermic reaction?
It is a reaction where there is a net adsorption of energy from a reaction.
It is a reaction where the products have more energy than the reactants.
It is a reaction that requires heat as a reactant.
all of the above
Which of the following is a correctly balanced equation?
2 P4 + 12 H2 → 8 PH3
0 P4 + 6 H2 → 4 PH3
P4 + 3 H2 → PH3
P4 + 6 H2 → 4 PH3
1 P4 + 6 H2 → 4 PH3
For the following balanced reaction, which of the following is a solid?
2 Na(l) + Cl2(g) → 2 NaCl(s)
NaCl
Cl
Na
Cl2
2 Na
What is the mass of an oxygen atom, O, in atomic mass units?
16 amu
12 amu
18 amu
32 amu
How does a catalyst increase the rate of a reaction?
It increases the energy difference between the reactants and products.
It is neither created nor consumed in a reaction.
It raises the activation energy of the reactants, which makes the reaction proceed faster.
It has nothing to do with the rate of reaction.
It lowers the activation energy.
Which of the following statements best describes the concept of entropy?
Energy has a tendency to remain in one place.
The energy released in a chemical reaction is the same as the difference in the energy of the bonds broken and formed.
The entropy of the universe is constantly decreasing.
Energy has a tendency to disperse.
Energy is neither created nor destroyed.
For the following balanced reaction, which of the following is a gas?
If it takes energy to break bonds and you gain energy in the formation of bonds, how can some reactions be exothermic while others are endothermic?
Some products have more energy than others and they always require energy to be formed.
Some reactants have more energetic bonds than others and they will always release energy.
It is the total amount of energy that matters. Sometimes some bonds are stronger than others and so you gain or lose energy when you form them.
It is the total number of bonds that matters. Sometimes you create more bonds than you break and since all bonds have same amount of energy you gain or lose energy depending on the number of bonds.
Given the following generic chemical reaction, which is the reactant?
→ is the reactant.
X is the reactant.
Y is the reactant.
What is a chemical reaction?
when two solids mix together to form a heterogeneous mixture
when two liquids mix to form a homogeneous mixture
when a liquid undergoes a phase change and produces a solid
when one or more new compounds are formed by rearranging atoms
when a new element is formed by rearranging nucleons
Which is higher in an endothermic reaction: the potential energy of the reactants or the potential energy of the products?
The potential energy of the reactants is higher than the potential energy of the products.
The potential energy of the products is higher than the potential energy of the reactants.
In the early stages of the reaction the potential energy of the reactants is higher. In the later stages, the potential energy of the products is higher.
The potential energy of the reactants is the same as the potential energy of the products.
What are the formula masses of water, H2O; propene, C3H6; and 2-propanol, C3H8O?
water: 18 amu; propene: 44 amu; 2-propanol: 64 amu
water: 18 amu; propene: 40 amu; 2-propanol: 58 amu
water: 18 amu; propene: 42 amu; 2-propanol: 60 amu
water: 18 amu; propene: 42 amu; 2-propanol: 62 amu
What is a reaction rate?
It is the speed with which products form from the reactants
It is the ratio of the molecular masses of the elements in a given compound.
It is the balanced chemical formula that relates the number of product molecules to reactant molecules.
It is the ratio of the masses of products and reactants.
What is the mass of a water molecule, H2O, in atomic mass units?
3 amu
2 amu
According to the following balanced chemical equation, if you want to generate two moles of H2O, how many moles of O2 do you need?
2 H2 + O2 → 2 H2O
2
1
1/2
4
Why is it important for a chemist to know the relative masses of atoms?
There are not that many different kinds of atoms and so it's important to know how they relate to one another.
It provides information about how many atoms two samples have relative to each other
Because the mass of an atom is directly related to its chemical properties.
It provides an indication of how the different atoms will interact
What is an endothermic reaction?
It is a reaction where the products have more energy than the reactant
For the following balanced equation, which has the highest coefficient?
4 H2 + 2 C → 2 CH4
H2
H4
CH4
C
Which of the following materials is most likely to undergo reduction?
Cl-
Na+
both A and B
For the following acid-base reaction, identify what compound is formed in the space marked.
HNO3 + KOH ⇌ ???? + H2O
KNO3
KOH2
H3ONO3
KOH2NO3
For each of the following unbalanced equations, which is depicted: oxidation or reduction?
a) Cr → Cr3+ b) Sn → Sn(OH)42-
a) reduction; b) oxidation
a) reduction; b) reduction
a) oxidation; b) reduction
a) oxidation; b) oxidation
Which of the following solutions is the most acidic?
a solution with a pH = 10
a solution with a pH = 14
a solution with a pH = 7
a solution with a pH = 4
All of the solutions are basic.
Which of the following statements describes a basic solution?
[H3O+] [OH-]
[H3O+] × [OH-] ≠ 1 × 10-14
[H3O+]/[OH-] = 1
[H3O+] > [OH-]
[H3O+]/[OH-] = 1 × 10-14
What is a base?
Anything with a bitter taste.
Anything that can be used to clean drains.
Anything that accepts a hydroxide ion.
Anything that accepts a hydrogen ion.
Anything that donates a hydroxide ion.
For the following reaction, identify whether the compound in bold is behaving as an acid or a base.
H3PO4 + H2O ⇌ H2PO4- + H3O+
acid
base
neither
both
According to the following reaction, which molecule is acting as an acid?
H3O+ + HSO4- → H2O + H2SO4
H2SO4
HSO4-
H2O
H3O+
What is an acid?
Anything that accepts hydrogen atoms.
Anything that donates hydrogen atoms.
Anything that donates hydrogen ions.
Anything that dissolves metal.
Anything that donates hydronium ions.
How many electrons are gained or lost in the following half-reaction?
Na → Na+
1/2 electron is gained
2 electrons are gained
1 electron is lost
1/2 electron is lost
1 electron is gained
What is a reduction?
the formation of red compounds in the presence of an oxidant
the gain of electrons
the reaction of oxygen with a reductant
the loss of an electron from the valence shell
the reduction of the number of electrons
What is oxidation?
the reduction of oxygen
the loss of electrons
the addition of an electron to the valence shell
the gaining of electrons
the reaction with oxygen
How is electrolysis different from what is going on chemically inside a battery?
You cannot make pure compounds with electrolysis.
Electrolysis does not use electrons.
You do not produce a chemical change in electrolysis.
They are the same process, just reversed.
Electrolysis only uses electrons from a cathode.
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.
The acid forms the positive ion, the base forms the negative ion.
Because different substances can act as an acid or a base, it depends on the substance you begin with.
According to the following reaction, which molecule is acting as a base?
Which of the following statements is not true about a neutralization reaction?
One molecule of acid neutralizes one molecule of base.
A neutralization is the reaction of a hydroxide ion with a proton.
Water is always formed in a neutralization reaction.
All of the above are true.
None of the above are true.
Which of the following statements describes a neutral solution?
Cl2 → 2 Cl-
4 electrons are gained
2 electrons are lost
H2O + NH3 → OH- + NH4+
NH4+
OH-
NH3
Which of the following statements about electrochemistry is not true?
It involves the use of a set of oxidation-reduction reactions to produce electrical current.
It is the study of how electrical energy and chemical reactions are related.
It involves the use of electrical current to produce an oxidation-reduction reaction.
It is the study of how electrons are transferred from one chemical compound to another.
What element is oxidized in the following equation and what element is reduced?
Sn2+ + 2 Ag → Sn + 2 Ag⁺
The tin ion, Sn2+, is oxidized, while the silver, Ag, is reduced.
Both the tin ion, Sn2+, and the silver, Ag, are reduced.
Both the tin ion, Sn2+, and the silver, Ag, are oxidized.
The tin ion, Sn2+, is reduced, while the silver, Ag, is oxidized.
OH- + NH4+ → H2O + NH3
HCl + KOH ⇌ ???? + H2O
H3OCl
KOH2Cl
KCl
Is it possible to have a macroscopic sample of oxygen that has a mass of 14 atomic mass units?
No, because oxygen is a gas at room temperature.
Yes, but it would have the same density as nitrogen.
No, this is less than than the mass of a single oxygen atom.
Yes, but it would need to be made of oxygen atoms that each had less than the normal number of neutrons.
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.
The density decreases as a function of temperature and this leads to an increase in volume which drops the rate of reaction.
The molecules are less reactive at higher temperatures.
The molecules will more likely combine with other atoms at high temperature to save space.
A refrigerator delays the spoilage of food by
diminishing the supply of oxygen to microorganism
slowing down the rate of chemical reactions within microorganisms.
expanding the water found within microorganisms.
killing microorganisms.
The ________ is what needs to be overcome in a reaction so that it can proceed to the products.
catalyst
thermodynamics
bond energy
activation energy
entropy
Which of the following statements about catalysts is NOT true?
A catalyst does not change the energy of the reactants or the products.
A catalyst can be used to speed up slow reactions.
A catalyst alters the rate of a chemical reaction.
A catalyst can be consumed in a reaction as long as it is regenerated.
What is the formula mass of sulfur dioxide, SO2?
about 32 amu
about 60 amu
about 16 amu
about 64 amu
What coefficient is needed in front of the O2 molecule to balance the following equation?
2 C4H10 (g) + _____ O2 (g) → 8CO2 (g) + 10 H2O (l)
5
13
8
How is Avogadro's number related to the numbers on the periodic table?
The periodic table tells you the mass of one atom. From that, and Avogadro's number you know the number of moles.
The mass listed is Avogadro's number.
The masses are all divisible by Avogadro's number, which gives you the weight of one mole.
The periodic table only gives us atomic numbers, not atomic mass.
The atomic mass listed is the mass of Avogadro's number's worth of atoms.
What is wrong with the following depiction of a chemical reaction?
One box contains more atoms than the other.
One box contains more molecules than the other.
These boxes contain only molecules but no atoms.
All of the above.
What is the mass of one mole of H2?
6.022 × 1023 g
1 g
20 g
2 g
Why is heat often added to chemical reactions performed in the laboratory?
to increase the rate at which reactant collide
to compensate for the natural tendency of energy to disperse
to allow a greater number of reactants to pass over the activation energy
Which equations are balanced? a) Mg (s) + 2HCl (aq) → MgCl2 (aq) + H2 (g) b) 3Al (s) + 3 Br2 (l) → Al2Br3 (s) c) 2HgO (s) → 2 Hg (l) + O2 (g)
Only equation "c" is balanced.
Equations "b" and "c" are balanced.
Equations "a" and "c" are balanced.
All of them are balanced.
According to the following balanced chemical equation, if you want to generate two moles of H2O how many grams of O2 do you need?
32
16
How does formula mass differ from atomic mass?
The atomic mass of a substance is the sum of the formula masses of the elements is its chemical formula. The atomic mass is the mass of a single atom.
The formula mass is the mass of the chemical formula and the atomic mass is the mass of the molecule.
They represent the same thing.
The formula mass of a substance is the sum of the atomic masses of the elements is its chemical formula. The atomic mass is the mass of a single atom.
Which of the following has the greatest number of particles?
1 mole of Be
1 mole of Na
9.012 g of Be
22.990 g of Na
All are the same.
Which of the following statements describes an acidic solution?
2 Na → 2 Na+
Which of the following statements is untrue about oxidation and reduction processes?
Often ions are generated or consumed.
An oxidation can happen without a reduction.
It involves the exchange of electrons.
Electrons are often involved in oxidation and reduction reactions.
Which of the following statements about oxidation and reduction reactions is true?
Only neutral atoms are formed in oxidation and reduction reactions.
More than one electron can be transferred in an oxidation and reduction reaction.
A half-reaction is only used for reduction reactions.
In a half-reaction, only half of an electron is transferred.
Zn → Zn+2
Which of the following compounds would least likely act as an acid?
HSO4-1
SO4-2
CH3CO2H
In the reaction below, what does the symbol ⇌ mean?
OH- + NH4+ ⇌ H2O + NH3
It means that the backward reaction happens as fast as the forward reaction and so the proton is not transferred at all.
It means that the forward and backward reactions are happening at the same time.
It means that the forward reaction does not progress.
It means that the reaction cannot decide which way to go.
Qualitatively, what happens to the hydroxide ion concentration if you decrease the hydronium ion concentration?
The concentration of OH- increases.
The concentration of OH- stays the same but the ratio OH-/H3O+ changes.
The concentration of OH- increases but the ratio stays the same.
How do you make a proton out of a hydrogen atom?
remove a proton from a helium nucleus
let the hydrogen atoms undergo fusion
let the hydrogen atoms combine to form a hydrogen molecule and eject a proton
remove an electron from a hydrogen atom
let the hydrogen atoms combine to form a hydrogen molecule and eject an electron
What is the formula mass of a molecule of CO2?
118 amu
56 amu
44 amu
58.9 amu
Some reactions are more sluggish than others. To speed up these reactions and save energy a(n) ________ is sometimes added.
heat source
activator
reaction profile
exotherm
Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?
125 kJ/mole
What is a chemical equation?
It is the sum of the masses of the products and reactants.
It is any type of reaction that takes place at the equator.
It is a picture of the atoms undergoing a chemical equalization.
It is the chemical combination of equal numbers of reactants and products.
It is a shorthand notation for illustrating a chemical reaction.
Balance the following equation. ____ NO → ____ N2O + _____ NO2
3, 0, 0
1, 2, 4
3, 1, 1
4, 4, 8
6, 2, 1
According to the following balanced chemical equation, if you want to generate two moles of H2O , how many molecules of O2 do you need?
6.022 × 10^23
a solution with a pH = 13
a solution with a pH = 12
For the following acid-base reaction, identify what is formed in the space marked.
HF + KOH ⇌ ???? + H2O
H3OF
KF
KOH2F
As the pH increases, the hydroxide ion concentration ________.
gets larger
goes down
stays constant
starts to decrease because it is reacting with the excess hydronium ions
starts to affect the H+ concentration
H2O + H2SO4 → H3O+ + HSO4-
