CHE 101 01 Unit 4 Exam
According to the law of conservation of matter, we must have the same number and type of atoms after the chemical change as were present before the chemical change.
True
Combustion reactions are redox reactions.
True
What is the purpose of a salt-bridge?
to allow ions to migrate between solutions
Which of the following reaction energies is the least exothermic (but still an exothermic reaction)?
-125 kJ/mole
In the chemical reaction H2SO4 + 2NaOH → Na2SO4 + 2H2O, the coefficient of sodium sulfate is _____.
1
Fourteen grams of nitrogen (atomic mass 14 amu) contains ________.
1 mole of nitrogen atoms
What would the concentration of [OH- ] be if the concentration of [H3O+] was 1 × 10-8M?
1 × 10-6 M
What would the concentration of OH- be if the concentration of H3O+ was 1 × 10-5M?[H3O+]× [OH-] = Kw = 1 × 10-14
1 × 10-9
What is the formula mass (also called molecular weight) of C6H12O6?
180 amu
A major source of chlorine gas, Cl2, is from the electrolysis of brine, which is concentrated salt water, NaCl (aq).Which of the following is the balanced chemical reaction for this electrolysis reaction?
2 NaCl (aq) + 2 H2O → 2 NaOH (aq) + Cl2 (g) + 2 H2 (g)
How many electrons are gained or lost in the following half-reaction? 2 Na → 2 Na+
2 electrons are lost
How many electrons are gained or lost in the following half-reaction? Zn → Zn2+
2 electrons are lost
Which of the following is an endothermic reaction?
2SnCl2 + 33 kcal Sn + SnCl4
How many moles of H2 bonds are broken if you react nitrogen with hydrogen according to the following reaction? N2 + 3H2 → 2 NH3
3
How many electrons are gained or lost in the following half-reaction? C → C4-
4 electrons are gained
How many oxygen molecules are needed to make 10 carbon dioxide molecules according to the following balanced chemical equation? 2 CO + O2 → 2 CO2
5
If the relative mass of a hydrogen atom is 1/4 that of a helium atom, how many helium atoms would you need to equal the mass of 200 hydrogen atoms?
50
In the reaction below, how many molecules of CO2 can be made from 30 molecules of oxygen?C6H12O6 + 6O2 →
6H2O + 6CO2 30
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 has the greatest number of particles?
All are the same.
Which of the following has the greatest number of particles? 1 mole of Na, 22.990 g of Na, 9.012 g of Be, 1 mole of Be
All of these
Which of the following statements is untrue about oxidation and reduction processes?
An oxidation can happen without a reduction.
Why don't the electrodes of a fuel cell deteriorate the way the electrodes of a battery do?
As long as fuel is supplied, fuel cells don't run down, but car batteries die when the electron-producing chemicals are consumed.
Which of the following is not necessarily shown in a chemically balanced equation?
Atomic number
Why is the anode of a battery indicated with negative (-) sign?
Because that is where electrons are being generated.
Which of the following can be considered an exothermic process?
Burning piece of paper
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.
For the following balanced reaction, which of the following is a gas? 2 Na(l) + Cl2(g) → 2 NaCl(s)
Cl2
Which of the half-reactions below would be complementary and balance the following half-reaction? Zn+2 → Zn
Cu → Cu2+
In the balanced redox reaction: 2 Cu(s) + S(s) → Cu2S(s), how many electrons are gained or lost by each copper atom?
Each copper atom loses one (1) electron
The law of conservation of energy states that
Energy cannot be created or destroyed.
What is the primary difference between a fuel cell and a battery?
Fuel cells do not run down because they can be refueled; batteries run down and need to be recharged.
In one type of fuel cell the following oxidation-reduction reactions are taking place:2 H2 + O2 → 2 H2O What is the fuel ?
H2
According to the following reaction, which molecule is acting as a base?
HSO4-
Identify the species that is oxidized and the species that is reduced in the reaction: 2 I- + Cl2 → 2 Cl- + I2
I- is oxidized and Cl2 is reduced.
What is the main characteristic of a strong acid?
It is completely dissociated in water.
What is the main characteristic of a strong base?
It is completely dissociated in water.
How does a catalyst increase the rate of a reaction?
It lowers the activation energy.
How are photovoltaic cells different from many other forms of solar energy?
Light is converted directly to electricity.
What are the two half reactions that show how many electrons are gained or lost by each species in the reaction:
Ni2+(aq) + 2 e- → Ni(s) and Mg(s) → Mg2+(aq) + 2 e-
Iron is useful for reducing copper ions to copper metal. Might it also be used to reduce sodium ions to sodium metal?
No, because sodium ions are too difficult to reduce.
In the balanced redox reaction: 2 C2H6(g) + 7 O2(g) → 4 CO2(g) + 6 H2O(g), which species is reduced?
O2(g)
Which of the following compounds could never act as an acid?
SO4-2
What do the brackets in the following equation represent?[H3O+]× [OH-] = Kw
The brackets mean the molarity of the compound inside them.
How might electrolysis be used to raise the hull of a sunken ship?
The gaseous products of the electrolysis of water could be collected with large bags attached to the hull of the ship. As the bags inflate with the gas they are buoyed upward pulling the ship also upward.
Why might coating a metal with another metal that is harder to oxidize prevent the first metal from being oxidized?
The metal that is coated is protected from moisture and oxygen so it doesn't react.
Why is carbon dioxide able to be stored more effectively in ocean water vs. fresh water?
The pH of the ocean is pretty high and so the carbon dioxide is trapped in a neutralization reaction.
How might warmer oceans accelerate global warming?
The solubility of CO2 in water decreases as temperatures rise.
In redox reactions, metals tend to undergo oxidation.
True
Photosynthesis is the process by which plants use solar energy to convert carbon dioxide and water to glucose.
True
The equation CH4 + 2O2 → CO2 + H2O is balanced.
True
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.
In a battery, the following two oxidation-reduction reactions are taking place:
Zn
Which of the following statements describes a basic solution?
[H3O+]< [OH-]
Which of the following statements describes an acidic solution?
[H3O+]> [OH-]
Which of the following items would you use to make an acidic buffer solution?
acetic acid (a weak acid) and sodium acetate
Cutting back on the pollutants that cause acid rain is one solution to the problem of acidified lakes. Suggest another.
add a neutralizing substance such as limestone
Which of the following items would you use to make a basic buffer solution?
ammonium hydroxide (a weak base) and ammonium chloride
What is a base?
anything that accepts a hydrogen ion
In a chemical equation the coefficients ________.
appear before the chemical formulas
Carbon dioxide reacts with water to form ________
carbonic acid
Some reactions are more sluggish than others. To speed up these reactions and save energy a(n) ________ is sometimes added.
catalyst
In a battery, the following two oxidation-reduction reactions are taking place:
rxn A
If the rate at which we produce CO2 were to stop rising, the levels of CO2 in the atmosphere would ________.
continue to rise
In the following buffer system, what happens to the concentration of the highlighted molecule if you add base (OH-)?
decreases
During combustion, the oxygen atoms of oxygen molecules ________.
gain a negative charge
The elements that make the best reducing agents are the ________.
group 1 alkali metals
The overall rate at which humans are producing carbon dioxide is ________.
increasing
The hydronium ion, H3O+, is a ________.
polyatomic ion
The hydroxide ion, HO-, is a ________.
polyatomic ion
If the oceans became acidic, they would start to ________.
release more CO2, which would raise the pH
What is a reduction?
the gain of electrons
What is the activation energy?
the minimum amount of energy to break the bonds in reactants
What is a chemical reaction?
when one or more new compounds are formed by rearranging atoms
At what point will a buffer solution cease to moderate changes in pH?
when the acting buffering component is all neutralized
What is a reduction?
ƒthe gain of cns
