CHEM 3U UNIT 2 Student note 2017 A (2)

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UNIT 2

Chemical Reactions

4.1 Recognizing and understanding chemical changes

Goals

*chemical change:

How do we know when a chemical reaction is taking place?

1) Change in colour

: some reactions produce a product that is a different colour

than any of the reactants.

2) Formation of a gas

: some reactions produce a gas. This gas can usually be seen

as bubbles escaping from solution.

3) Formation of a solid

: sometimes, when two solutions are mixed together, a

solid is produces. This solid is called a precipitate.

4) Release or Absorption of heat

: some chemicals release heat when reacting

together, while others absorb it.

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*In a chemical reaction:

1. Conservation of mass and charge

Ie// the mass of reactants is equal to the mass of products

and

the charge on the left hand side of the equation must be equal to the charge

on the right.

Example: 2H

2

+ O

2

 2H

2

O

4 H atoms 4 H atoms

2 O atoms 2 O atoms

Mechanism for chemical reactions

*

N O O O O O N O O O

no reaction

reaction

Representing chemical change

*chemical equation used to condense a word equation

Example:

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(2) 2 hydrogen molecules + 1 oxygen molecule yields 2 water molecules

2H

2

(g) + O

2

(g)  2H

2

O(l)

2 molecules of hydrogen gas will react with 1 molecule of oxygen gas to

produce 2 molecules of water. (2, 1, and 2 are coefficients)

reactions that require a catalyst

*

*catalyst: a substance that increases the rate of a chemical reaction but is not

consumed (used up) in the reaction. It is NOT a reactant or a product.

2H

2

O

2

(aq)  2H

2

O(l) + O

2

(g)

slow reaction

2H

2

O

2

(aq)

MnO2

2H

2

O(l) + O

2

(g)

rapid reaction

*MnO

2

is a catalyst

HOMEWORK: Read p. 147 Going green with chemistry, complete #1- 4

Read p. 150 The effects of chemical reactions, complete #1-4

p. 155, 2-5

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4.2 and 4.3 Synthesis and Decomposition Reactions

Goals

1) Synthesis Reactions

:

-occur when 2 or more substance combine to

produce a more complex substance

A + B  AB

*4 types:

a) Reactions of elements.

b) Reactions that produce acids

c) Reactions that produce bases

d) Reactions that produce salts

2) Decomposition Reactions

:- reverse of an addition reaction

-a compound is broken down (decomposed) to

give 2 or more simpler substances.

AB  A + B

a) Decomposition that produces elements (rare)

b) Decomposition of acids

c) Decomposition of bases

d) Decomposition of salts

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4.4 Single Displacement Reactions

Goals

*a reaction in which one element replaces another in a compounds.

*Example:

Fe(s) + CuSO

4

 FeSO

4

+ Cu

Activity Series

*each metal will displace any metal ion that appears below it in the series.

COMPLETE: Investigation 4.4.2 – Developing an Activity Series pg. 180

Examples:

1. 2Al + Fe

2

O

3



2. Zn(s) + Mg(NO

3

)

2

(aq) 

Activity Series for Halogens

Fluorine

Chlorine

most

Bromine

reactive

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Examples

1)

Predict the products

Cl

2

(g) + 2NaBr(aq) 

2)

Predict the products

I

2

(s) + NaCl(aq) 

Applications

1) This process is used in mining industry

*Copper Recovery Plant: solutions of CuSO

4

are reacted with scrap iron.

The iron displaces the copper, giving solid copper metal. Since copper is

more valuable than iron, this reaction is economically feasible.

2) Corrosion and protection

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4.6 Double Displacement Reactions

Goals

*always involves two ionic compounds

*the cation of one compound changes places with the cation of the second

compound

AB + CD  AD + CB

*types of double displacement reactions

1) Precipitation Reactions

:

CaCl

2

(aq) + Na

2

CO

3

(aq)  CaCO

3

(s) + 2NaCl(aq)

*

How to predict if a precipitate will form?

Solution: homogeneous mixture of a solute and solvent

Solvent: medium

Na+ Cl

Cl-_Na+

Solute: substance dissolved

*

*solubility table (table 1, p. 173) shows solubility of a large # of ionic

compound.

*used to test for the presence of certain ions.

2) Reactions producing gas

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3) Neutralization Reactions

*

Ma(OH)

2

(s) + 2HCl(aq)  MgCl

2

(aq) + 2H

2

O(l)

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5.1 and 5.3 Combustion AND Elements and Their Oxides

Goals

1) Combustion

:

Element

Common oxides

C

CO

2

H

2

O

S

SO

2

N

NO

2

Example: CH

4

(g) + 2O

2

(g)  CO

2

(g) + 2H

2

O(g)

Combustion and the atmosphere:

*burning of fossil fuels produces carbon dioxide

*greenhouse effect

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2) Incomplete combustion

In class, indicate the following information on this note outline. Provide an

underlined heading for each of the following.

-provide a definition from pg. 193

-indicate a desirable application pg. 194

-explain why incomplete combustion produces a greater variety of products

-provide 2 examples of the incomplete combustion of heptanes

-summarize 3 concerns related to incomplete combustion

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Complete: Mini Investigation- Exploring Bunsen burner Combustion p.195

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Using a Bunsen burner

Safety:

 You must wear goggles  Long hair must be tied up

 The Bunsen burner must be placed on black table top Work in pairs

Collect your equipment:

- Goggles - Hair elastic - Bunsen burner -Fuel lighter

1. Check connections to burner and desk outlet valve. 2. Close needle valve and collar.

3. Open desk outlet valve fully. 4. Open needle valve 1/2 turn.

5. Use the fuel lighter to light the flame.

6. Adjust collar and needle valve till you see a blue flame.

Type of Flame When do we use this flame?

Air hole open

Air hole half open

Air hole closed

The Bunsen Burner

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Type of Flame When do we use this flame?

Air hole open _{Roaring flame} _{To heat things up fast}

Air hole half open Blue flame To heat things up gently

Air hole closed Safety flame

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A Voyage through Equations

Name ________________ Per.

Section 1: Identify the type of reaction

For the following reactions, indicate whether the following are examples of synthesis(S), decomposition(D), combustion(C), single displacement(SD) or double displacement(DD).

1) Na3PO4 + 3 KOH  3 NaOH + K3PO4 _____________

2) MgCl2 + Li2CO3 MgCO3 + 2 LiCl _____________

3) C6H12 + 9 O2 6 CO2 + 6 H2O _____________

4) Pb + FeSO4 PbSO4 + Fe _____________

5) CaCO3 CaO + CO2 _____________

6) P4 + 3 O2 2 P2O3 _____________

7) 2 RbNO3 + BeF2 Be(NO3)2 + 2 RbF _____________

8) 2 AgNO3 + Cu  Cu(NO3)2 + 2 Ag _____________

9) C3H6O + 4 O2 3 CO2 + 3 H2O _____________

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11) SeCl6 + O2 SeO2 + 3Cl2 _____________

12) 2 MgI2 + Mn(SO3)2 2 MgSO3 + MnI4 _____________

13) 2 NO2 2 O2 + N2 _____________

14) C6H6 + __ O2 __ H2O + __ CO2 (Balance this one) _____________

Five Types of Chemical Reaction Worksheet

Balance the following reactions and indicate which of the five types of chemical reaction are being represented:

1) ____ NaBr + ____ Ca(OH)2 ___ CaBr2 + ____ NaOH