Chemical ReactionsChemical Reactions

Chapter 13

Homework AssignmentHomework AssignmentChap 13Chap 13

Review Questions (p 290): 1 – 23Review Questions (p 290): 1 – 23

Multiple Choice Questions: 1 - 10Multiple Choice Questions: 1 - 10

3 ways of representing the reaction of H2 with O2 to form H2O

Chemical reaction - process in which one or more substances is changed into one or more new substances.

reactants products

Chemical equation - uses chemical symbols to show what happens during a chemical reaction

How to “Read” Chemical Equations

2 H2 (g) + O2 (g) 2 H2O (l)

How to “Read” Chemical Equations

2 molecules H2 + 1 molecule O2 makes 2 molecules H2O

2 moles H2 + 1 mole O2 makes 2 moles H2O

IS NOT

2 grams H2 + 1 gram O2 makes 2 g H2O

2 H2 (g) + O2 (g) 2 H2O (l)

• Chemical reactions only involve the rearrangementChemical reactions only involve the rearrangementof atoms. Atoms are of atoms. Atoms are not created or destroyednot created or destroyed in inchemical reactions.chemical reactions.

• Chemical equations must be balanced!Chemical equations must be balanced!

Balancing Chemical Equations

Methane reacts with oxygen to form carbon dioxide and water

Change the numbers in front of the formulas (coefficients) to make the number of atoms of each element the same on both sides of the equation. Do not change the subscripts.

2H2O NOT H4O2

CH4 (g) + O2 (g) → CO2 (g) + H2O (l)

CH4 (g) + 2O2 (g) → CO2 (g) + 2H2O (l)

Fe (s) + O2 (g) → Fe2O3 (s)

4Fe (s) + 3O2 (g) → 2Fe2O3 (s)

Examples of balancing equations

H2 (g) + N2 (g) → NH3 (g)

3H2 (g) + N2 (g) → 2NH3 (g)

AcidsAcids

• Have a sour taste. Vinegar owes its taste to acetic acid.Have a sour taste. Vinegar owes its taste to acetic acid.Citrus fruits contain citric acid.Citrus fruits contain citric acid.

• React with certain metals to produce hydrogen gas.React with certain metals to produce hydrogen gas.

• React with carbonates and bicarbonates to produce carbon React with carbonates and bicarbonates to produce carbon dioxide gas.dioxide gas.

• Cause color changes in plant dyes.Cause color changes in plant dyes.

2HCl (2HCl (aqaq) + Mg () + Mg (ss) MgCl) MgCl22 ( (aqaq) + H) + H22 ( (gg))

2HCl (2HCl (aqaq) + CaCO) + CaCO33 ( (ss) CaCl) CaCl22 ( (aqaq) + CO) + CO22 ( (gg) + H) + H22O (O (ll))

• Aqueous acid solutions Aqueous acid solutions (aq)(aq) conduct electricity. conduct electricity.

• Have a bitter taste.Have a bitter taste.

• Feel slippery. Many soaps contain bases.Feel slippery. Many soaps contain bases.

BasesBases

• Cause color changes in plant dyes.Cause color changes in plant dyes.

• Aqueous base solutions Aqueous base solutions (aq)(aq) conduct electricity. conduct electricity.

ammoniaammoniahydroxide ionhydroxide ion

(“milk of magnesia”)

acid - a hydrogen ion donorbase - a hydrogen ion acceptor

acid base

A hydrogen ion, H+, is the same as a proton!

Hydronium ion, hydrated proton, H3O+

Electron-rich region

Electron-poor region

Figure 13.3

HH

HHHH

OO

acidbase

acid - a hydrogen ion donorbase - a hydrogen ion acceptor

acid base

Neutralization Reaction

acid + base salt + water

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

SaltsSalts

HCl (aq) + KOH (aq) KCl (aq) + H2O