Chapter 4 Lecture Problems

Chapter 4: Chemical Quantities and Aqueous Reactions

4.1 Climate Change and the Combustion of Fossil Fuels

4.2 Reaction Stoichiometry: How Much Carbon Dioxide

Calculate the mass of phosphorous trichlorided produced when 0.01 moles of P₄ reacts with 0.06 moles of chlorine gas according to the balanced equation.

P₄ (s) + 6 Cl₂ (g) -> 4 PCl₃

P₄ (s) 6 Cl₂ (g) -> 4 PCl₃ (l)

Given (moles) 0.01 mole 0.06 mole

Use 0.01 mole 0.06 mole

Produce 0.04 mole

Final 0 mole 0 mole 0.04 mole

MW 123.895 g mole^-1 70.905 g mole^-1 137.332 g mole^-1

Given (mass) 1.24 g 4.25 g

Produce (mass) 5.49 g

4.3 Limiting Reactant, Theoretical Yield, and Percent Yield

Calculate the amount of product and reactant remaining in the video clip with the reaction of zinc metal and hydrochloric acid. ( Internet© Saunders, 1997). Assume all three use 1.0 moles of HCl, and that the flasks contain 1.0, 0.5 and 0.25 moles of zinc metal.

	Zn (s)	2 HCl (aq)	-->	Zn²⁺	H₂ (g)
Initial	1.0	1.0
Change	0.5	1.0		0.5	0.5
Final	0.5	0		0.5	0.5

	Zn (s)	2 HCl (aq)	-->	Zn²⁺	H₂ (g)
Initial	0.5	1.0
Change	0.5	1.0		0.5	0.5
Final	0	0		0.5	0.5

	Zn (s)	2 HCl (aq)	-->	Zn²⁺	H₂ (g)
Initial	0.25	1.0
Change	0.25	0.5		0.5	0.5
Final	0	0.25		0.25	0.25

Calculate the amount of product and reactant remaining when the following react according to the balanced chemical equation:
2 H₂ + O₂ -> 2 H₂O

Start with 10.00 g of each
Calculate limiting reagent
Calculate final values
If only 10.58 g H₂O what is the % yield

2 H₂ O₂ -> 2 H₂O

given (mass) 10.0 g 10.0 g

MW 2.016 g mole^-1 31.999 g mole^-1 18.015 g mole^-1

given (mole) 4.96 mole 0.312 mole

use 0.625 mole 0.312 mole

produce 0.625 mole

final (mole) 4.335 mole 0 mole 0.625 mole

final (mass) 8.74 g 0 g 11.26 g

Solid Rocket fuel used for the space shuttle is aluminum metal and ammonium perchlorate. These react to produce aluminum oxide, aluminum chloride, nitrogen monoxide, and water (SRB info from NASA).

Write out the chemical equation
Balance the chemical equation
Given 1.00 kg each reactant, which is limiting, what is the mass of each product.
Given 1.00 kg Al, how much NH₄ClO₄ should be used. What is the mass of products?

3 Al(s) + 3 NH₄ClO₄(s) -> Al₂O₃(s) + AlCl₃(s) + 3 NO(g) + 6 H₂O(g)

3 Al (s) 3 NH₄ClO₄ (s) -> Al₂O₃ (s) AlCl₃ (s) 3 NO (g) 6 H₂O (g)

given (gram) 1.00x10³ 1.00 x10³

MW (g mole^-1) 26.9815 117.4886 101.961 133.3396 30.0061 18.0152

given (mole) 37.06 8.51

use (mole) 8.51 8.51

produce (mole) 2.84 2.84 8.51 17.02

final (mole) 28.55 0 2.84 2.84 8.51 17.02

final (gram) 770. 0 290. 379 255 307

Over the years, the thermite reaction has been used for welding railroad rails, in incendiary bombs, and to ignite solid-fuel rocket motors (video clip from "The Chemistry Set") What masses of iron(III) oxide and aluminum are required for a theoretical yield of 15.0 g iron? What is the maximum mass of aluminum oxide that could be produced? How much aluminum oxide is actually produced from these starting materials if the yield is 93%? The thermite reaction is:

Fe₂O₃(s) + 2Al(s) -> 2Fe(l) + Al₂O₃(s)

Fe₂O₃(s) 2Al(s) -> 2Fe(l) Al₂O₃(s)

produce 15 g

MW 159.7 g/mole 26.98 g/mole 55.85 g/mole 102.0 g/mole

Produce 0.269 mole 0.134 mole

Need 0.134 mole 0.269 mol

Need 21.4 g 7.26 g

Yield (theoretical) 15 g 13.7 g

93% Yield 14.0 g 12.7 g

Elixirs such as Alka-Seltzer use the reaction of sodium bicarbonate with citric acid in aqueous solution to produce a fizz. Balance the following reaction.

What mass of C₆H₈O₇ should be used for every 1.0*10² mg of NaHCO₃?
If 1.0*10² mg of C₆H₈O₇ is used, which is the limiting reagent?
What mass of CO₂(g) could be produced by this mixture?
If only 45 mg of CO₂ is produced, what is the percent yield?
How many grams of Na₃C₆H₅O₇ is actually produced?

3 NaHCO₃(aq) 1 C₆H₈O₇ -> 3 CO₂ 3 H₂O 1 Na₃C₆H₅O₇(aq)

given 1.0*10² mg

given 0.10 g

MW 84.01 g/mole 192.1 g/mole 44.01 g/mole 18.02 g/mole 258.07 g/mole

given 1.19x10^-3 mole

need 3.97x10^-4 mole

need 0.076 g

produce 1.19x10^-3 mole 1.19x10^-3 mole 3.97x10^-4 mole

Yield (theoretical) 0.052 g 0.021 g 0.102 g

Actual Yield 0.045 g

% yield 86.5 %

Actual Yield 0.018 g 0.088 g

4.4 Solution Concentration and Solution Stoichiometry

NiCl₂*6H₂O ( internet)

8.320g NiCl₂*6H₂O
250.00 mL Volumetric Flask

Mass of Compound (NiCl₂*6H₂O) 8.320 g

MW (NiCl₂*6H₂O) 237.69 g mole^-1

Moles (NiCl₂*6H₂O) 0.0350 mole

Volume (NiCl₂*6H₂O) 250.0 mL

Concentration (NiCl₂*6H₂O) 0.140 mole liter^-1

What happens to ions? internet

Concentration Ni²⁺ 0.140 mole liter^-1

Concentration Cl^1- 0.280 mole liter^-1

How to produce 500.0 mL of 0.0100 M K₂Cr₂O₇ (aq)

Concentration (K₂Cr₂O₇ (aq) ) 0.0100 M

Volume (K₂Cr₂O₇ (aq) ) 500.0 mL

Moles (K₂Cr₂O₇ (aq) ) 0.00500 mole

MW (K₂Cr₂O₇ (aq) ) 294.18 g mole^-1

mass (K₂Cr₂O₇ (aq) ) 1.471 g

Concentration K¹⁺ 0.0200 M

Concentration Cr₂O₇^2- 0.0100 M

How do you prepare 100 mL of 0.150 M caffeine (C₈N₄O₂H₁₀)?
How do you prepare 1.50 L of 3 M Mg²⁺ from Magnesium nitrate?

Dilution

0.100 M K₂Cr₂O₇ 2.00 mL diluted to 500 mL

( internet )

Initial Concentration (K₂Cr₂O₇ (aq) ) 0.100 mole liter ^-1

Volume (K₂Cr₂O₇ (aq) ) 2.00 mL

Moles (K₂Cr₂O₇ (aq) ) 0.000200 mole

Dilution Volume 500 mL

Final Concentration (K₂Cr₂O₇ (aq) ) 0.000400 mole liter^-1

0.140 M NiCl₂ (aq) solution

Dilute 2.00 mL to 500 mL

Initial Concentration NiCl₂ 0.140 mole liter^-1

Volume NiCl₂ 2.00 mL

Moles NiCl₂ 2.8x10^-4 mole

Final Volume NiCl₂ 500 mL

Final Concentration NiCl₂ 5.6x10^-4 mole liter^-1

Dilute 5.00 mL to 500 mL

Initial Concentration NiCl₂ 0.140 mole liter^-1

Volume NiCl₂ 5.00 mL

Moles NiCl₂ 7.0x10^-4 mole

Final Volume NiCl₂ 500 mL

Final Concentration NiCl₂ 1.4x10^-3 mole liter^-1

Dilute 5.00 mL to 250 mL

Initial Concentration NiCl₂ 0.140 mole liter^-1

Volume NiCl₂ 5.00 mL

Moles NiCl₂ 7.0x10^-4 mole

Final Volume NiCl₂ 250 mL

Final Concentration NiCl₂ 2.8x10^-3 mole liter^-1

Dilute 5.00 mL to 1.00 L

Initial Concentration NiCl₂ 0.140 mole liter^-1

Volume NiCl₂ 5.00 mL

Moles NiCl₂ 7.0x10^-4 mole

Final Volume NiCl₂ 1.00 L

Final Concentration NiCl₂ 7.0x10^-4 mole liter^-1

4.5 Types of Aqueous Solutions and Solubility

4.6 Precipitation Reactions

4.7 Representing Aqueous Reactions: Molecular, Ionic, and Complete Ionic Equations

4.8 Acid-Base and Gas-Evolution Reactions

Magnesium Hydroxide + Nitric Acid

Balanced total equation: Mg(OH)₂ (aq) +2 HNO₃(aq)-> 2 H₂O +Mg(NO₃)₂ (aq)
Total Ionic Equation: Mg²⁺ + 2 OH^1- + 2 H¹⁺ + 2NO₃^1- - > 2H₂O + Mg²⁺ + 2 NO₃^1-
Net Ionic Equation 2 OH^1- + 2 H¹⁺ -> 2H₂O

Sulfuric acid and lithium hydroxide

Total equation: H₂SO₄ (aq) + 2 LiOH (aq) -> 2 H₂O + Li₂SO₄ (aq)
Ionic Equation: 2 H¹⁺ (aq) + SO₄^2- (aq) + 2 LI¹⁺ (aq) + 2 OH^1- -> 2 H₂O + SO₄^2- (aq) + 2 Li¹⁺ (aq)
Net ionic equation 2 H¹⁺ (aq) + 2 OH^1- -> 2 H₂O

Acetic acid and iron (III) hydroxide

Total equation: 3 CH₃COOH (aq) + Fe(OH)₃ (s) -> 3 H₂O + Fe(CH₃COO)₃ (aq)
Ionic Equation: 3 CH₃COO^1- + 3H¹⁺ (aq) + Fe³⁺(aq) + 3 OH^1- (aq) ->
3 H₂O + Fe³⁺ (aq) + 3 CH₃COO^1- (aq)
Net ionic equation: 3H¹⁺ (aq) + 3 OH^1- (aq) -> 3 H₂O

Ammonia (NH₃) and water( Internet)
NH₃ + H₂O -> NH₄¹⁺ (aq)+ OH^1-(aq)
hydrochloric acid and ammonia produces ammoinum and chloride
HCl (aq) + NH₃(aq) - > NH₄¹⁺ (aq) + Cl^1-(aq)
hydrochloric acid and sodium hydroxide produces sodium chloride and water; no indicator
HCl(aq) + NaOH(aq)-:gt; H₂O + NaCl(aq)

4.9 Oxidation-Reduction Reactions

This page is maintained by
Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

This page has been accessed times since 5/30/97.
Last Updated Friday, May 25, 2001 2:10:36 PM

	P₄ (s)	6 Cl₂ (g)	->	4 PCl₃ (l)
Given (moles)	0.01 mole	0.06 mole
Use	0.01 mole	0.06 mole
Produce				0.04 mole
Final	0 mole	0 mole		0.04 mole
MW	123.895 g mole^-1	70.905 g mole^-1		137.332 g mole^-1
Given (mass)	1.24 g	4.25 g
Produce (mass)				5.49 g

	2 H₂	O₂	->	2 H₂O
given (mass)	10.0 g	10.0 g
MW	2.016 g mole^-1	31.999 g mole^-1		18.015 g mole^-1
given (mole)	4.96 mole	0.312 mole
use	0.625 mole	0.312 mole
produce				0.625 mole
final (mole)	4.335 mole	0 mole		0.625 mole
final (mass)	8.74 g	0 g		11.26 g

	3 Al (s)	3 NH₄ClO₄ (s)	->	Al₂O₃ (s)	AlCl₃ (s)	3 NO (g)	6 H₂O (g)
given (gram)	1.00x10³	1.00 x10³
MW (g mole^-1)	26.9815	117.4886		101.961	133.3396	30.0061	18.0152
given (mole)	37.06	8.51
use (mole)	8.51	8.51
produce (mole)				2.84	2.84	8.51	17.02
final (mole)	28.55	0		2.84	2.84	8.51	17.02
final (gram)	770.	0		290.	379	255	307

	Fe₂O₃(s)	2Al(s)	->	2Fe(l)	Al₂O₃(s)
produce				15 g
MW	159.7 g/mole	26.98 g/mole		55.85 g/mole	102.0 g/mole
Produce				0.269 mole	0.134 mole
Need	0.134 mole	0.269 mol
Need	21.4 g	7.26 g
Yield (theoretical)				15 g	13.7 g
93% Yield				14.0 g	12.7 g

	3 NaHCO₃(aq)	1 C₆H₈O₇	->	3 CO₂	3 H₂O	1 Na₃C₆H₅O₇(aq)
given	1.0*10² mg
given	0.10 g
MW	84.01 g/mole	192.1 g/mole		44.01 g/mole	18.02 g/mole	258.07 g/mole
given	1.19x10^-3 mole
need		3.97x10^-4 mole
need		0.076 g
produce				1.19x10^-3 mole	1.19x10^-3 mole	3.97x10^-4 mole
Yield (theoretical)				0.052 g	0.021 g	0.102 g
Actual Yield				0.045 g
% yield				86.5 %
Actual Yield					0.018 g	0.088 g

Mass of Compound (NiCl₂*6H₂O)	8.320 g
MW (NiCl₂*6H₂O)	237.69 g mole^-1
Moles (NiCl₂*6H₂O)	0.0350 mole
Volume (NiCl₂*6H₂O)	250.0 mL
Concentration (NiCl₂*6H₂O)	0.140 mole liter^-1
What happens to ions?	internet
Concentration Ni²⁺	0.140 mole liter^-1
Concentration Cl^1-	0.280 mole liter^-1

Concentration (K₂Cr₂O₇ (aq) )	0.0100 M
Volume (K₂Cr₂O₇ (aq) )	500.0 mL
Moles (K₂Cr₂O₇ (aq) )	0.00500 mole
MW (K₂Cr₂O₇ (aq) )	294.18 g mole^-1
mass (K₂Cr₂O₇ (aq) )	1.471 g

Concentration K¹⁺	0.0200 M
Concentration Cr₂O₇^2-	0.0100 M

Initial Concentration (K₂Cr₂O₇ (aq) )	0.100 mole liter ^-1
Volume (K₂Cr₂O₇ (aq) )	2.00 mL
Moles (K₂Cr₂O₇ (aq) )	0.000200 mole
Dilution Volume	500 mL
Final Concentration (K₂Cr₂O₇ (aq) )	0.000400 mole liter^-1

Initial Concentration NiCl₂	0.140 mole liter^-1
Volume NiCl₂	2.00 mL
Moles NiCl₂	2.8x10^-4 mole
Final Volume NiCl₂	500 mL
Final Concentration NiCl₂	5.6x10^-4 mole liter^-1