Ch 10 Chemical Reactions

p. 276-291

We need to know:

1. Recognize chemical change

2. Represent reactions with equations

3. Balance Chemical Equations

4. Classify reactions and their characteristics

Define Vocabulary: All words on p. 303 except – complete ionic equation, net ionic equation, solute, solvent, spectator ion.

Write this down:

1. The process by which the atoms of one or more substances are rearranged to form different substances is called a chemical reaction. (ch. rxn.)

2. Chemical reaction=chem. Change

3. Evidence of chem.rxn-temperature change, release of energy in form of light or heat, getting cooler; color change (tarnish), odor, gas bubbles, new solid appears (precipitate);

4. Reactants-starting substances, on the left side

5. Products- substances formed, on the right side

6. Arrow means “yields” or “produces”

7. Plus sign shows reaction between 2 or more reactants

8. Symbols are used to show physical state: (s), (g), (l), (aq)

9. Skeleton equations have chemical formulas, but no coefficients. (not balanced)

Skeleton equation example:

H₂(g) + O₂(g) H₂0(g)

Balanced: 2H₂(g) + O₂(g) 2H₂0(g)

Practice:

Write the skeleton equations for:

1. hydrogen gas plus bromine gas yields hydrogen bromide gas

2. carbon monoxide gas plus oxygen gas yields carbon dioxide gas

3. potassium chlorate solid produces potassium chloride solid plus oxygen gas

Balanced chemical equations show the quantities of the reactants and the products are equal on each side of the arrow-as required by the law of conservation of mass.

Fe(s) + Cl₂(g) FeCl₃(s)

__Fe(s) + ___Cl₂(g) ___FeCl₃(s)

Coefficient- number written in front of each reactant or product. (1 is understood, not written) It describes the lowest whole-number ratio of the amounts of all the reactants and products.

Balanced equation:

2Fe(s) + 3 Cl₂(g) 2FeCl₃(s)

Balanced Chemical Equation is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a ch. rxn.+

YouTube lesson - http://www.youtube.com/watch?v=_B735turDoM

How:

1. Write the skeleton equation

2. list the elements &/or ions and tally the quantities on each side

3. adjust coefficients until all are equal

4. Check your work

Things to remember:

1. If you write the formula incorrectly, you cannot balance the equation correctly.

2. Write diatomic elements correctly.

3. Never change a subscript.

4. Write the coefficients in their lowest possible ratio.

Do St Guide p. 55-56

Turn it in for a grade

Quiz over Section 1 tomorrow- study your notes taken so far, as well as balancing equations

Section 2

Classifying Chemical Reactions

1. Synthesis p.284

A + B AB

2 or more reactants producing 1 product

Examples:

2Fe(s) + 3Cl₂(g) 2FeCl₃(s)

CaO(s) + H₂O(l) Ca(OH)₂(s)

2. Combustion p. 285

O₂ combines w/a substance & releases energy (heat/light)

Examples:

2H₂ (g) + O₂(g) 2 H₂O (g)

CH₄(g) + 2O₂(g) CO₂(g) + 2 H₂O(g)

3. Decomposition p. 286

Single reactant breaks down into 2 or more elements, cmpds.

AB A + B

· usually req’s addition of heat

· Examples:

NH₄NO₃(s) N₂O (g) + 2H₂O(g)

2NaN₃ (s) 2Na (s) + 3N₂(g)

4. Single Replacement p. 287

Atoms of one element replace the atoms of another element

AX + B A + BX

This is what we did in lab.

Example:

2Li(s) + 2 H₂O(l) 2LiOH (aq) + H₂(g)

*be sure to check the activity series to see if a reaction will take place

5. Double Replacement p. 290

Involves an exchange of ions between 2 reactants

AX + BY AY + BX

· produces a precipitate, gas, or water

Example:

2NaOH (aq) + CuCl₂(aq) 2 NaCl(aq) + Cu(OH)₂(s)

P. 291 Table 10-3

p.285 #14-26

Ch 10 Notes continued…

Lab: Single Replacement Reactions

(Activity Series)

Reactivity is the ability to gain or lose electrons

More “active” – loses e- more easily than less “active” metals

Activity Series – orders metals by their reactivity with other metals; the most active are those at the top of the list; least active is at the bottom; a specific metal can replace any metal listed below it that is in a compound, but it cannot replace any metal listed above it.

Sometimes a non-metal (halogen) will replace another non-metal (halogen) in a reaction. Consult the periodic table (group 7A) to determine reactivity. Fluorine is at the top of the group, therefore it is most active. Reactivity decreases downward.

v If you were absent make sure that you turn in any make up work that you owe.

v Today-Notes over 10.2

v Copy the activity series to the back of your Periodic Table.

v Homework: Read Lab & Do Study Guide 10.2. Due tomorrow

v TAKS workbook p. 1-20
Lab: Single Replacement Reactions

Single Replacement p. 287

Atoms of one element replace the atoms of another element

AX + B A + BX

What you will do:

1.Predict if reaction will occur.(hypothesis)

2.Test your hypothesis.

3. Write balanced equations for the reactions.

4. Make an activity series for the metals that you tested.

Procedure:

Change to procedure:

Use Well Plates instead of test tubes.

Re-Number all three Data Tables:

Data Table 1
Test Tube Number	Indication of Chemical Reaction
1
3
6
8
9
11

Split the observation column into 3 columns. Write in the metal & soln. that you will be using in that well.

Leave the far right column blank for writing in your observations.

Data Table 1
Test Tube Number	Indication of Chemical Reaction Metal Solution
1	Pb	CuSO₄
3
6
8
9
11

v If there is no reaction, write NR.

Hypothesis: Predict which metals and solutions will NOT react. (Complete sentence)

On notebook paper, 1^st write your hypothesis, then answer Pre-lab questions # 1-3. Have this finished by 1^st of class tomorrow. (Complete sentence)

Staple the NB paper to lab.

Do not turn it in yet.