Upgrade to remove ads
Lesson 6: Practice Exercises
Terms in this set (31)
Explain how you can tell whether a chemical reaction has taken place.
Macroscopic changes that indicate the reaction has occurred are color changes,
odor changes, energy absorption or release, gas release, and precipitation of solids.
Write balanced chemical equations for the reactions described.
a) sodium metal + chlorine gas --> sodium chloride crystals
b) propane gas + oxygen --> carbon dioxide + water vapor + energy
c) zinc metal + hydrochloric acid --> zinc chloride solution + hydrogen
A. 2Na(s) + Cl2(g) → 2NaCl(s)
B. C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(g) + energy
C. Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
Why is it important to balance a chemical equation?
The law of conservation of mass must be obeyed in a chemical reaction. For mass
to be balanced on both sides of an equation that represents a reaction, the numbers
and kinds of atoms present in the products must be the same as those present in
In the reaction of carbon with oxygen, one carbon atom reacts with on molecule of oxygen to form one molecule of carbon dioxide. If you react 20 billion atoms of carbon with 30 billion molecules of oxygen, will all the reactants be used up? What do you think the results will be?
If the carbon atoms and oxygen molecules react in a 1:1 ratio, then 20 billion
molecules of oxygen would react with 20 billion atoms of carbon to produce 20
billion molecules of carbon dioxide. There would be 10 billion oxygen molecules
In the catalytic converter of a car, a reaction occurs when nitrogen monoxide gas, NO, reacts with hydrogen gas. Ammonia gas and water vapor are formed. Write a balanced equation for this reaction.
2NO(g) + 5H2(g) → 2NH3(g) + 2H2O(g)
Explain why classifying reactions can be useful.
Recognizing patterns of changes that take place during a reaction helps you predict
changes that might occur in a new reaction that fits one of the patterns.
Using different symbols to represent different atoms, draw pictures to represent an example of each of the following kinds of reactions.
c) single displacement
d) double displacement
A. α + β → αβ
B. αβ → α + β
C. α + βγ → αγ + β
D. αβ + γδ → αδ + γβ
E. αβ + γγ → αγ + βγ
Classify each of the following reactions.
a) N2O4(g) --> 2NO2(g)
b) 2Fe(s) + O2(g) --> 2FeO(s)
c) 2Al(s) +3Cl2(g) --> 2AlCl3(s)
d) BaCl2(aq) + Na2SO4(aq) --> BaSO4(s)+ 2NaCl(aq)
e) Mg(s) +CuSO4(aq) --> MgSO4(aq)
D. double displacement
E. single displacement
When a candle burns, wax undergoes a combustion reaction, Would a candle burn longer in the open or when covered with an inverted glass jar? Explain.
A candle would burn longer in the open. Burning wax is a combustion reaction
which requires oxygen as a reactant.
When a fungus breaks down the wood in a fallen tree, the biological process is called decomposition. What does that process have in common with he chemical decomposition reaction type?
Both types of decomposition involve breaking down more complex materials into
simpler ones. The fungus gets energy and nutrients by breaking down large
carbohydrate and protein molecules in the wood.
List and describe four factors that can influence the rate of a reaction.
Answers may include temperature—raising the temperature increases reaction rate;
concentration—increasing the concentration of one or more reactants increases
reaction rate; catalysts—adding a catalyst increases reaction rate; inhibitors—adding
an inhibitor decreases reaction rate.
Explain whether an exothermic reaction that is at equilibrium will shift to the left or to the right to readjust after each of the following procedures is followed.
a) Products are removed.
b) More reactant are added.
c) More heat is added.
d) Heat is removed.
A. to the right
B. to the right
C. to the left
D. to the right
Explain the difference between an inhibitor and a catalyst.
An inhibitor decreases the rate of a reaction, but a catalyst increases the rate of
Hydrogen gas can be produced by the reaction of magnesium and hydrochloric acid, as shown by this equation.
Mg(s) + 2HCl(aq) --> MgCl2(aq) + H2(g)
In a particular reaction, 6 billion molecules of HCl were mixed with 1 billion atoms of Mg.
a)Which reactant is limiting?
b) How many molecules of H2 are formed when the reaction is complete.
B. 1 billion molecules
Catalytic converters on cars use the metals rhodium and platinum as catalysts to convert potentially dangerous exhaust gases to carbon dioxide, nitrogen, and water. Why don't cars need to have the rhodium and platinum replaced after they are used.
The metals provide a surface on which the reaction can take place, but the metals
themselves are not used up in the reaction.
One which side of the arrow are the products of a reaction usually found? One which side are the reactants found?
Change these descriptions of reactions to balanced chemical equations.
a) Butane vapor in a handheld lighter burn in oxygen to form water vapor and carbon dioxide.
b) Dinitrogen tetroxide gas decomposes into nitrogen dioxide gas.
c) Solid lithium metal reacts with oxygen gas to form solid lithium oxide.
d) Aqueous solutions of sulfuric acid and potassium hydroxide undergo a double displacement reaction.
A. 2C4H10(g) + 13O2 → 10H2O(g) + 8CO2(g)
B. N2O4(g) → 2NO2(g)
C. 4Li(s) + O2(g) → 2Li2O(s)
D. H2SO4(aq) + 2KOH(aq) → K2SO4(aq) + 2H2O(l)
Explain why subscripts should never be change when balancing an equation.
Changing subscripts changes the chemical identities of the substances involved.
Which of the five general types of reactions has only one reactant?
Hydrogen gas and iodine gas combine in a reversible exothermic reaction to form hydrogen iodide gas.
a)Write a word equation for this reaction.
b) Write a balance chemical equation for this reaction. c) If more iodine gas is added after the reaction reaches equilibrium, will the reaction be shifted to the left or the right?
d) If heat is added after the reaction reaches equilibrium, will the reaction be shifted to the left or the right?
A. hydrogen + iodine R hydrogen iodide + energy
B. H2(g) + I2(g) R 2HI + energy
C. to the right
D. to the left
List all the macroscopic change that occur while a cake is made that indicate that chemical reactions have occurred.
Answers may include changes in odor, color, size, taste, and texture.
Few biochemical reactions occurring in our cells reach equilibrium. Most of the time, it is to our advantage to almost completely form products from reactants. Would our cells get more energy from the exothermic combustion of the sugar glucose if the reaction goes to completion or reaches and equilibrium?
Our cells get more energy if glucose completely combusts; if it reaches equilibrium,
some of the energy is not released.
Catalytic converters help break down pollutants that result from gasoline combustion and are required in automobiles in the United States. Most catalytic converters contain a platinum-rhodium catalyst that coats the extensive surface of a honeycomb structure in the converter. Why would having the catalyst spread out over a large surface area be useful?
The larger the surface area over which a catalyst is spread, the more reactants that
can associate with the catalyst and undergo reaction at the faster rate.
If you place a piece of a saltine cracker on your tongue for a few minutes, it begins to taste sweet. Do you think a chemical or physical change leads to this taste change? Why?
Taste change would indicate that a substance has changed identity, which indicates
a chemical change.
Why are high temperature and pressure needed for the Haber process?
The N2 and H2 molecules must be close enough (increased pressure) for there to be
many collisions, and the molecules must be moving fast enough (increased
temperature) that the collisions result in a reaction.
When do you think it might be important that light sticks come in different colors?
Your answer might include that different colors could have different meanings. For
example, if used as a distress signal, yellow could signify one type of problem and
green could signify another type.
Explain why it is best to store many chemicals in tightly sealed bottles in dark locations at cool or moderate temperatures.
A tightly sealed bottle keeps reactive substances in the air away from the chemicals
so they can't react with them. Storing chemicals at low temperatures slows down
the rate at which they react to form other compounds. The dark bottle reduces
light, which is a catalyst for some reactions.
Does the reaction taking place in MiniLab 1 go to completion, or does it reach and equilibrium? Ho do you know?
It goes to completion because energy does not continue to be produced.
Compare the charges, masses, and atomic locations of electrons, protons, and neutrons. (Ch.2)
Electrons: negative charge, light, move around nucleus; Protons: positive charge,
heavier, found in nucleus; Neutrons: no charge, same mass as proton, found in
Explain why KCl is commonly used as a substitute for NaCl, rather than using another chloride such as CaCl2 or CsCl. (Ch.3)
Because potassium and sodium are in the same column of the periodic table and
are just one row apart, the properties of KCl will be more similar to those of NaCl
than will those of other chlorides.
Compare properties of ionic and covalent compounds. (Ch.5)
Ionic: hard, brittle, electrolytes, high melting points; Covalent: hard or soft,
nonelectrolytes, usually lower melting points.
THIS SET IS OFTEN IN FOLDERS WITH...
Lesson 2: Practice Exercises
Lesson 4: Practice Exercises
Lesson 7: Practice Exercises
Quest study guide pos
YOU MIGHT ALSO LIKE...
Chemistry - Module 6
Lab quiz 4: Stoichiometric Calculations and Reacti…
physical science Ch 6 review
physical science Ch 6 review
OTHER SETS BY THIS CREATOR
Lesson 9: Practice Exercises
Lesson 5: Practice Exercises
Lesson 1: Practice Exercises
OTHER QUIZLET SETS
booster questions anatomy (module 1)
Chapters 1-6 Reviews
Chemistry: Unit 10