nwtc general chemistry ch 08

Chapter 8

Introduction to General, Organic, and Biochemistry 10e

John Wiley & Sons, Inc

Morris Hein, Scott Pattison, and Susan Arena

Chemical EquationsFlames and sparks resultwhen aluminum foil is droppedInto liquid bromine.

Chapter Outline

Copyright 2012 John Wiley & Sons, Inc

8.1 The Chemical Equation

8.2 Writing and Balancing Chemical Equations

8.3 Information in a Chemical Equation

8.4 Types of Chemical Equations

8.5 Heat in Chemical Reactions

8.6 Global Warming: The Greenhouse Effect

The Chemical Equation

Chemical shorthand for a chemical reaction.

1. Reactants Products

2. Whole number coefficients indicate numbers of each substance participating in the reaction.

3. Special conditions for the reaction are often written over the arrow. (Δ means heat is supplied to the reaction.)

4. Physical states of each substance are indicated.


4Al(s) + 3O2(g) 2Al2O3(s)

Review Question 1: Purpose of balancing chemical reaction?

The Chemical Equation


Mg(s) + 2HCl(aq) H2(g) + MgCl2(aq)

NaOH(aq) + HCl(aq) H2O(l) + NaCl(aq)

Review Question 6

Your Turn!

In the reaction: CuSO4 + BaBr2 CuBr2 + BaSO4

a. BaBr2 and BaSO4 are reactants

b. BaSO4 and CuBr2 are products

c. CuSO4 and BaSO4 are reactants

d. CuSO4 and BaBr2 are products


Writing and Balancing Chemical Equations

A balloon filled with a hydrogen and oxygen gas explodes when heated. The product is water vapor.

1. Identify the reaction

2. Write the unbalanced equation

3. Balance the equation

A balanced equation has the same number of each kind of atom on each side of the equation.


H2(g) + O2(g) H2O(g)

H2(g) + O2(g) H2O(g)22R 2 H 2 O

P 2 H 1 O

R 2 H 2 O

P 4 H 2O

R 4 H 2 O

P 4 H 2 O

Hydrogen gas + oxygen gas water gas

R = reactantsP = products

Review Question 2: What do the numbers in front represent?


Phosphorus burns in air to produce diphosphorus pentoxide.





P4 + O2 P2O5

2

phosphorus + oxygen diphosphorus pentoxide

P4 + O2 P2O5

Hint: Start with most complex compound.

R 4 P 2 O

P 2 P 5 O

R 4 P 2 O

P 4 P 10 O

R 4 P 10 O

P 4 P 10 O5

Review Question 5: How do you account for the atoms?

Your Turn!

Given the unbalanced equation:

HCl + NH3 NH4Cl

When properly balanced, the sum of the balancing coefficients is

a. 7

b. 5

c. 3

d. 4

e. 6


HCl + NH3 NH4Cl

Your Turn!


NH3 H2 + N2


a. 3

b. 6

c. 9

d. 12


2NH3 3H2 + N2


Zinc metal reacts with silver nitrate to produce zinc nitrate and silver metal.





Zn + AgNO3 Zn(NO3)2 + Ag

22R 1 Zn 1 Ag 1 NO3

P 1 Zn 1 Ag 2 NO3

zinc + silver nitrate zinc nitrate + silver

Zn + AgNO3 Zn(NO3)2 + AgR 1 Zn 2 Ag 2 NO3

P 1 Zn 1 Ag 2 NO3

R 1 Zn 2 Ag 2 NO3

P 1 Zn 2 Ag 2 NO3

Hint: Balance polyatomic ions as a unit.

*Your Turn!


Co + CuSO4 Co2(SO4)3 + Cu


a. 6

b. 7

c. 8

d. 9

e. 10


2Co + 3CuSO4 Co2(SO4)3 + 3Cu

Your Turn!


Al(OH)3 + H2SO4 Al2(SO4)3 + H2O


a. 4

b. 9

c. 12

d. 24


2Al(OH)3 + 3H2SO4 Al2(SO4)3 + 6H2O


Ethylene burns in air to produce carbon dioxide and water.





C2H4 + O2 CO2 + H2O

R 2 C 4 H 2 O

P 1 C 2 H 2+1 O

ethylene + oxygen carbon dioxide + water

C2H4 + O2 CO2 + H2O

Hint: Balance hydrogen and oxygen last.

R 2 C 4 H 2 O

P 2 C 2 H 4+1 O

R 2 C 4 H 2 O

P 2 C 4 H 4+2 O2 2R 2 C 4 H 6 O

P 2 C 4 H 4+2 O3

Acetylene (C2H2) burns in air to produce carbon dioxide and water.





C2H2 + O2 CO2 + H2OR 2 C 2 H 2 O

P 1 C 2 H 2+1 O

acetylene + oxygen carbon dioxide + water

C2H2 + O2 CO2 + H2O

Hint: Use a fraction to balance O, then multiply all coefficients by two to eliminate the fraction.

22( )5

2

R 2 C 2 H 2 O

P 2 C 2 H 4+1 O

2 C2H2 + 5 O2 4 CO2 + 2 H2O

R 2 C 2 H 5 O

P 2 C 2 H 4+1 O

R 4 C 4 H 10 O

P 4C 4 H 8+2 O

Your Turn!


C2H6 + O2 CO2 + H2O


a. 23

b. 19

c. 17

d. 9

e. 13


2C2H6 + 7O2 4CO2 + 6H2O

Your Turn!


C3H8 + O2 CO2 + H2O


a. 7

b. 9

c. 15

d. 23

e. 13


C3H8 + 5O2 3CO2 + 4H2O

Information in a Chemical Equation


Information in a Chemical Equation

How many moles of HF can be made from 2 moles of hydrogen gas and 2 moles of fluorine gas?

4 moles of hydrogen fluoride gas

What is conserved?

Atoms!Copyright 2012 John Wiley & Sons, Inc

H2(g) + F2(g) 2HF(g)

1 molecule 1 molecule 2 molecules

2 atoms H 2 atoms F 2 atoms H + 2 atoms F

1 mol H2 1 mol F2 2 mol HF

Review Question 3

Your Turn!

How many molecules of oxygen gas are needed to burn 2 molecules of propane according to the balanced equation ?

a. 5 molecules of oxygen

b. 6 molecules of oxygen

c. 10 molecules of oxygen

d. 15 molecules of oxygen


C3H8 + 5O2 3CO2 + 4H2O

Types of Chemical Equations

1. Combination Reactions

2. Decomposition Reactions

3. Single-Displacement

4. Double-Displacement


A + B AB

AB A + B

A + BC B + AC or A + BC C + BA

A B+ CD AD + CB

Combination Reactions

1. metal + oxygen metal oxide

2Mg(s) + O2(g) 2MgO(s)

4Fe(s) + 3O2(g) 2Fe2O3(s)

2. nonmetal + oxygen nonmetal oxide

C(s) + O2(g) CO2(g)

2N2(s) + O2(g) 2N2O (g)


A + B AB


3. metal + nonmetal salt

2Al(s) + 3Br2(l) 2AlBr3(s)

2K(s) + I2(s) 2KI(s)

4. metal oxide + water metal hydroxide

K2O(s) + H2O(l) 2KOH(aq)

SrO(s) + H2O(l) Sr(OH)2(aq)


A + B AB


5. nonmetal oxide + water oxy-acid

SO3(g) + H2O(l) H2SO4(aq)

P2O5(s) + 3H2O(l) 2H3PO4(aq)

N2O5(s) + H2O(l) 2HNO3(aq)


A + B AB

AB A + B

Decomposition Reactions


1. Metal oxides decompose into metals and oxygen gas.

2HgO(s) 2Hg(l) + O2(g)

2PbO2(s) 2PbO(s) + O2(g)

2. Metal carbonates form metal oxides and CO2.

Na2CO3(s) Na2O + CO2(g)

3. Metal bicarbonates form metal carbonates, CO2 and H2O.

NaHCO3(s) Na2CO3(s) + CO2(g) + H2O(g)

4. Other examples:

2Hg2O2(aq) 2H2O(l) + O2(g)

2NaClO3(s) 2NaCl(s) + 3O2(g)

AB A + B

Decomposition Reactions


Single Displacement Reactions

If A is a metal: A + BC B + AC

If A is a nonmetal: A + BC C + BA

Zn(s) + 2HCl(aq) ZnCl2(aq) + H2(g)

When pieces of zinc metal are placed

in hydrochloric acid, hydrogen

bubbles form immediately.


Activity Series

More active elements can replace less

active elements.


2Al(s) + 3CuCl2(aq) 2AlCl3(aq) + 3Cu (s)

Hg(l) + CuSO4(aq) no reaction

Review Question 7 a

Review Question 7 b

Your Turn!


Consider the following reactions:

A(s) + HCl(aq) no reaction

B(s) + 2HCl(aq) BCl2(aq) + H2(g)

What is the correct activity series?

a. least active A < B < H most active

b. least active A < H < B most active

c. least active B < H < A most active


1. Metal + acid H2 + salt

Fe(s) + 2HCl(aq) FeCl2(aq) + H2 (g)

Cu(s) + HCl(aq) no reaction

2. metal + water H2 + metal oxide

or metal hydroxide

2K(s) + 2H2O(l) 2KOH(aq) + H2 (g)

3Fe(s) + 4H2O(g) Fe3O4(s) + 4H2 (g)



3. Metal + salt metal + saltSn(s) + 2AgNO3(aq) Sn(NO3)2(aq) + Ag(s)

Zn(s) + AlCl3(aq) no reaction

4. halogen + halide salt halogen +

halide salt

F2(g) + 2NaCl(aq) 2NaF(aq) + Cl2 (g)

I2(s) + 2NaCl(aq) no reaction


Your Turn!

The reaction: Ba(s) + PtCl2(aq) BaCl2(aq) + Pt(s), will occur if

a. Pt is more active than Ba

b. Ba is more active than Pt

c. Ba is more active than O

d. O is more active than Pt


Your Turn!

The likely products of the reaction between Al and NiCl2 are

a. AlNi and Cl2

b. AlCl2 and Ni

c. AlCl and Ni

d. AlCl3 and Ni

e. no reaction


Double Replacement Reactions

A B+ CD AD + CB

Cations exchange anionsPb(NO3)2(aq) + 2KI(aq) PbI2(s) + 2KNO3(aq)

Evidence of chemical change:

1. Evolution of heat

2. Formation of precipitate

3. Formation of gas bubbles


Neutralization Reactions

Double replacement: A B+ CD AD + CB

acid + base salt + water + heat

HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l)

Detected by increase in temperature (release of heat).

H2SO4(aq) + Ba(OH)2(aq) BaSO4(s) + 2H2O(l)

Detected by increase in temperature and formation of a cloudy precipitate.


Metal Oxide + Acid Reactions


metal oxide + acid salt + water

Heat is released by the production of water

ZnO(s) + 2HCl(aq) ZnCl2(aq) + H2O(l)

Na2O(s) + 2HCl(aq) 2NaCl(aq) + H2O(l)


Precipitation Reactions


An insoluble product (precipitate) is formed and indicated by placing an (s) after its formula in the equation.

Check the solubility table in Appendix V to

see if a precipitate forms.

BaCl2(aq) + Na2SO4(aq) BaSO4(s) + 2NaCl(aq)


2NaCl(aq) + Hg2(NO3)2(aq) 2NaNO3(aq) + Hg2Cl2(s)

Gas Forming Reactions


NaCl(s) + H2SO4(l) NaHSO4(s) + HCl(g)

Na2S(aq) + 2HCl(aq) H2S(g) + 2NaCl (s)

H2SO4(aq) + 2NaCN(aq) Na2SO4(aq) + 2HCN(g)

Double replacement reactions that form H2CO3, H2SO3 or NH4OH are quickly followed by the decomposition of these compounds into gases (indirect gas production).


Indirect Gas Forming Reactions

metal carbonate + acid salt + CO2(g) + H2O(l)

Na2CO3(aq) + 2HCl(aq) 2NaCl(aq) + CO2(g) + H2O(l)

metal sulfite + acid salt + SO2(g) + H2O(l)

Na2SO3(aq) + 2HCl(aq) 2NaCl(aq) + SO2(g) + H2O(l)

ammonium salt + base salt + NH3(g) + H2O(l)

NH4NO3(aq) + NaOH(aq) NaNO3(aq) + NH3(g) + H2O(l)


Your Turn!

What are the likely products of the reaction of copper(II) oxide with nitric acid?

a. CuNO3 + H2O

b. Cu(NO3)2 + H2O

c. Cu(NO2)2 + H2O

d. CuNO2 + H2O


CuO(s) + 2HNO3(aq) Cu(NO3)2(aq) + H2O(l)

Your Turn!

What are the likely products of the reaction of sodium sulfide with iron(III) chloride?

a. FeS + NaCl

b. FeS3 + NaCl

c. Fe3S + NaCl

d. Fe2S3 + NaCl


2FeCl3(aq) + 3Na2S(aq) Fe2S3(s) + 6NaCl(aq)

Your Turn!

What are the likely products of the reaction of sodium hydrogen carbonate with hydrochloric acid?

a. NaCl + H2CO3

b. NaCl + H2O + CO2

c. NaCl + H2O + CO3

d. NaCl + H2 + CO3


NaHCO3(aq) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)

Heat in Chemical Reactions

Endothermic vs Exothermic

Endothermic reactions absorb heat

O2(g) + N2(g) + 181 kJ 2NO(g)

Exothermic reactions release heat

2 Al(s) + Fe2O3(s) 2Fe(s) + Al2O3(s) + 852 kJ

The amount of heat absorbed or released is the

heat of reaction.

Copyright 2012 John Wiley & Sons, IncReview Question 4

Endothermic Reactions


Exothermic Reactions


Your Turn!

Consider the reaction: H2 + I2 + 12.6 kJ 2 HI. When one mole of HI is produced

A. 12.6 kJ of energy is absorbed

B. 6.3 kJ of energy is absorbed

C. 12.6 kJ of energy is released

D. 6.3 kJ of energy is released


Global Warming: The Greenhouse Effect


Global Warming: The Greenhouse Effect

Increased carbon dioxide levels have caused a 0.74°C rise in global temperatures over the last 100 years.


http://www.wiley.com/college/hein/0471741531/image_galleries/ch08/pages/fig_08_05.htm

Questions

Review Questions – Did in class

Paired Questions (pg 164)– Do 1, 3, 7, 9, 11, 15, 21, 27, 29, 31, 35 , 39, 43– Practice later 2, 6, 12, 16, 20, 24, 28, 32, 36, 40, 44

Copyright 2012 John Wiley & Sons, Inc 1-48

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