Question 1

Balance the following equation for the combustion of benzene: 
C6H6(l) + O2(g) F1F1F1S1F1F1F10 H2O(g) + CO2(g)

Accepted Answer

A)  C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 3H2O(g) + 6CO2(g) 
B)  C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 6H2O(g) + 6CO2(g) 
C)  2C6H6(l) + 15O2(g) F1F1F1S1F1F1F10 6H2O(g) + 12CO2(g) 
D)  C6H6(l) + 15O2(g) F1F1F1S1F1F1F10 3H2O(g) + 6CO2(g) 
E)  2C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 6H2O(g) + 12CO2(g) 
A)  C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 3H2O(g) + 6CO2(g) 
B)  C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 6H2O(g) + 6CO2(g) 
C)  2C6H6(l) + 15O2(g) F1F1F1S1F1F1F10 6H2O(g) + 12CO2(g) 
D)  C6H6(l) + 15O2(g) F1F1F1S1F1F1F10 3H2O(g) + 6CO2(g) 
E)  2C6H6(l) + 9O2(g) F1F1F1S1F1F1F10 6H2O(g) + 12CO2(g)

Question 2

Consider the balanced equation for the combustion of propane, C3H8
 C3H8(g) + 5O2(g) F1F1F1S1F1F1F10 3CO2(g) + 4H2O(l)
If propane reacts with oxygen as above
a. what is the limiting reagent in a mixture containing 5.00 g of C3H8 and 10.0 g of O2?
b. what mass of CO2 is formed when 1.00 g of C3H8 reacts completely?

Accepted Answer

a. Oxygen

Question 3

Phosphorus pentachloride, PCl5, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl5.

Accepted Answer

A)  5.38 mol 
B)  3.55 mol 
C)  0.583 mol 
D)  0.282 mol 
E)  0.186 mol 
A)  5.38 mol 
B)  3.55 mol 
C)  0.583 mol 
D)  0.282 mol 
E)  0.186 mol

Question 4

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO3(s) F1F1F1S1F1F1F10 KCl(s) + O2(g) [unbalanced]
How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

Accepted Answer

A)  223 g 
B)  99.1 g 
C)  10.3 g 
D)  6.86 g 
E)  4.60 g 
A)  223 g 
B)  99.1 g 
C)  10.3 g 
D)  6.86 g 
E)  4.60 g

Question 5

What is the percent yield for the reaction PCl3(g) + Cl2(g) F1F1F1S1F1F1F10 PCl5(g)
If 119.3 g of PCl5 (M = 208.2 g/mol) are formed when 61.3 g of Cl2 (   = 70.91 g/mol) react with excess PCl3?

Accepted Answer

A)  195% 
B)  85.0% 
C)  66.3% 
D)  51.4% 
E)  43.7% 
A)  195% 
B)  85.0% 
C)  66.3% 
D)  51.4% 
E)  43.7%

Question 6

One mole of methane (CH4) contains a total of 3 × 1024 atoms.

Accepted Answer

A) True 
 B)False

Question 7

The iodine "clock reaction" involves the following sequence of reactions occurring in a reaction mixture in a single beaker.
1) IO3-(aq) + 5I-(aq) + 6H+(aq) F1F1F1S1F1F1F10 3I2(aq) + 3H2O(l)
2) I2(aq) + 2S2O32-(aq) F1F1F1S1F1F1F10 2I-(aq) + S4O62-(aq)
The molecular iodine (I2) formed in reaction 1 is immediately used up in reaction 2, so that no iodine accumulates. In one experiment, a student made up a reaction mixture which initially contained 0.0020 mol of iodate ions (IO3-). If the iodate ions reacted completely, how many moles of thiosulfate ions (S2O32-) were needed in reaction 2, in order to react completely with the iodine (I2) produced in reaction 1?

Accepted Answer

A) 0)0020 mol 
B) 0)0030 mol 
C) 0)0040 mol 
D) 0)0050 mol 
E) 0)0060 mol 
A) 0)0020 mol 
B) 0)0030 mol 
C) 0)0040 mol 
D) 0)0050 mol 
E) 0)0060 mol

Balance the following equation for the combustion of benzene: C₆H₆(l) + O₂(g)  H₂O(g) + CO₂(g)

Phosphorus pentachloride, PCl₅, a white solid that has a pungent, unpleasant odor, is used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl₅.

Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and potassium chloride when heated. KClO₃(s)  KCl(s) + O₂(g) [unbalanced] How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

What is the percent yield for the reaction PCl₃(g) + Cl₂(g)  PCl₅(g) If 119.3 g of PCl₅(M = 208.2 g/mol) are formed when 61.3 g of Cl₂( = 70.91 g/mol) react with excess PCl₃?

One mole of methane (CH₄) contains a total of 3 × 10²⁴ atoms.

Keys to the Study of Chemistry

The Components of Matter

The Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids, Solids, and Phase Changes

The Properties of Mixtures: Solutions and Colloids

Periodic Patterns in the Main Group Elements: Bonding, Structure, and Reactivity

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Equilibrium: the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Thermodynamics: Entropy, Free Energy, and the Direction of Chemical Reactions

Electrochemistry: Chemical Change and Electrical Work

The Elements in Nature and Industry

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

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Exam 3: Stoichiometry of Formulas and Equations

Balance the following equation for the combustion of benzene: C6H6(l) + O2(g)  H2O(g) + CO2(g)