mrsjeddore.weebly.commrsjeddore.weebly.com/uploads/6/...chemical_reactions_-_notes.… · Web viewWrite the word equations for each of the following chemical reactions: 1)When dissolved

February 9th, 2017 Name: _________________________

Unit 2: Chemical ReactionsNotes: Part 5

Introduction to Chemical Reactions

TEXT p. 218-219 (word equations)

Chemistry is all around us!Remember the graphic organizer you filled out on the first day?Go back and have a look!

There are many chemical reactions – too many to count in fact!

Like many other areas in science,chemical reactions have to be grouped to stay organized.

You know how we scientist types are about organization!

To group them – we must recognize patterns.

We have already grouped other things in chemistry:- Ionic vs. molecular- Acid vs. base

Being able to recognize the patterns in chemical reactions will help us to:

Understand the reaction Predict the products of similar reactions

FIRST:

We must lay the ground workand learn the conventions

Science 1206 Unit 3: Chemical Reactions Page 1 of 38

for representing a chemical reaction simply.

Word Equations

- Used to easily represent a chemical reaction using words and symbols

Generally:

all reactants all products

OR

reactant 1 + reactant 2 product 1 + product 2

Read as:

reactant one plus reactant two goes to product one plus product two

Example:

Complete: Try This Activity: Completing Word Equations p. 219


What do you notice?

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Homework- Questions p. 219 #’s 2, 3, 4a

Writing a Chemical Equation

If we are given a word equation


THEN

we are able to write a chemical equation by replacing the words with chemical formulas

(this is where all your naming practice comes in handy!)

State of matter

- We must also include the state for each compound in the reaction;- It goes in brackets after each chemical formula- Most of the time this information will be given in the word problem.- We will learn later how to use a solubility table.

Solid (s) – all solids including metals and precipitates

Liquid (l) – for pure liquids such as water

Gas (g) – gaseous substances like many molecular compounds

Aqueous (aq) – compounds dissolved in water (solutions) including acids

- Activity: Worksheet – Writing Chemical Equations (pages 5, 6 and 7)



Writing Chemical EquationsWrite the word equations for each of the following chemical reactions:


1) When dissolved beryllium chloride reacts with dissolved silver nitrate in water, aqueous beryllium nitrate and silver chloride powder are made.

2) When isopropanol (C3H8O) burns in oxygen, carbon dioxide, water, and heat are produced.

3) When dissolved sodium hydroxide reacts with sulfuric acid (H2SO4), aqueous sodium sulfate, water, and heat are formed.

4) When fluorine gas is put into contact with calcium metal at high temperatures, calcium fluoride powder is created in an exothermic reaction.

5) When sodium metal reacts with iron (II) chloride, iron metal and sodium chloride are formed.

The Law of Conservation of Mass

TEXT p. 222-223 (conserving mass)


Think about some of the chemical reactions you are familiar with like:A nail becoming rusty – rust is added - nail gains massWood burning in your woodstove – all that’s left is a few ashes - mass is lost

In fact, it seems like mass is gained or lost in many reactions.

However:Through much experimentation,scientists have discovered that

mass is NOT gained or lost in any chemical reaction.Rather, it is conserved.

Every Single Time!

That is:Mass of the reactants = the mass of the

productsALWAYS

This has become known as:

The Law of Conservation of Mass- In a chemical reaction the total mass of the reactants is always equal to the total mass

of the products

Let’s revisit our woodstove example…


And getting a little more technical…

Homework

- Questions p. 223 # 1-4 Balancing Chemical Equations

TEXT p. 226-229 (balancing chemical equations)

What does this tell us about the number and type of atoms in the reactants versus the number and type of atoms in the products?


They MUST be the same – exactly the same…ALWAYS

During the chemical reaction the atoms become rearranged to form new products.

Because the oxygen atoms are not equal on the product side, we add another water molecule.

Now the hydrogen atoms are not equal on the reactant side, so we add another hydrogen molecule.

Look what we have:

BTW…- The numbers that we are placing in front of each compound to balance the equation are

called coefficients- They do NOT change the chemical formula


Let’s try this:

Check your answer:

Hints for balancing:

- It doesn’t matter which side of the chemical equation you start on.- It usually helps to start with an atom that there is the most of.- Gradually work your way back and forth from reactants to products side until all atoms are

balanced.- When balancing combustion reactions (hydrocarbon and oxygen) balance in the order of C-H-O.

Examples:



Activity: Worksheet – Balancing Equations (Double Sided – pages 13 and 14)


Unit 2: Chemical ReactionsNotes: Part 6

Solubility

So far we have learned many things about chemical reactions:- How to write them


- How to balance themNext:

- We must learn how to write the states for each compound in a chemical reaction.- We have already learned the abbreviations.

o Solid (s) – all solids including metals and precipitateso Liquid (l) – for pure liquids such as watero Gas (g) – gaseous substances like many molecular compoundso Aqueous (aq) – compounds dissolved in water (solutions) including acids

- Before, the solubility information would be given BUT in this section we will learn how to use the solubility table on the back of the periodic table to predict the solubility of

ionic compounds.Solubility Table

- Contains general solubility guidelines for ionic compounds

Can be used in just 2 easy steps!

Step 1: Look for the anion (negative ion) of the compound in the top of the columns.

Step 2: Look down the column to locate the cation (positive ion) and determine if it is in the…

- high solubility row - write (aq) after the compound in the chemical equation- low solubility row - write (s) after the compound in the chemical equation.

o HINT: this is generally the precipitate in the products!


TRY: Potassium chloride

Silver sulfate

Ammonium fluoride

Copper (II) acetate

Copper (I) acetate

Activity 2.18: Worksheet – Predicting Solubility (page 17)

Science 1206Unit 2: Chemical Reactions

Predicting Solubility - Worksheet

Place the subscript (s, l, g, aq) indicating the correct state of matter in the brackets at the end of each element/compound.

1. __ Cr2O3( ) __ Cr( ) + __ O2( )


2. __ Ni( ) + __ HCl( ) __ NiCl2 ( ) + __ H2( )

3. __ Ca(NO3)2( ) + __ Na3PO4 ( ) __ Ca3(PO4)2( ) + __ NaNO3( )

4. __ Al ( ) + __ O2 ( ) __ Al2O3 ( )

5. __ HCl ( ) + __ Ca(OH)2 ( ) __ HOH ( ) +__ CaCl2 ( )

6. __Zn ( ) + __ Pb(CH3COO)2 ( ) __ Pb( ) + __ Zn(CH3COO)2( )

7. __ HgO ( ) __ Hg ( ) +__ O2 ( )

8. __ NaI ( )+__ Pb(NO3)2 ( ) __ PbI2 ( )+ __ NaNO3 ( )

9. __ Cl2 ( ) +__ NaI ( ) __ I2 ( ) + __ NaCl ( )

10. __ Al2(SO4)3 ( ) + __ Ca(OH)2 ( ) __ Al(OH)3 ( )+ __ CaSO4 ( )

Types of Chemical Reactions

TEXT p. 230 (combustion)p. 233-235 (synthesis and decomposition)p. 240-241 (single/double replacement)

So far we have learned many things about chemical reactions:- How to write them- How to balance them- How to predict solubility

Next:


We must learn:- How to identify different types- How to predict products

All members of a chemical family react in a similar way

There are definite patterns in reactions

Knowledge of patterns is useful because:

o We will have a better understanding of chemical reactionso We can predict products of unknown reactions

Remember! You need to be able to PREDICT the products!

There are 5 types of chemical reactions that we will be studying.

1. Hydrocarbon Combustion- rapid reaction of a substance with oxygen to produce oxides- Often called burning- General Format: Hydrocarbon + oxygen carbon dioxide + water

Example:

Butane + oxygen carbon dioxide + water vapor

2C4H10 + 13 O2 8CO2 + 10 H2O

Balancing tip: Remember to balance in the order of C-H-O

Try these! Include:


- Word equation (if not already given)- Balanced chemical equation- States of matter

#1: Methane + oxygen carbon dioxide + water vapor

#2: Kerosene C14H30 (l) under goes complete combustion.

Activity: Worksheet – Combustion Reactions (page 20)


2. Synthesis- also called combination or formation reactions- combination of smaller atoms or compounds to form 1 larger compound (product)- General Format: A + B AB- Often elements combine to form compounds


Examples:Hydrogen + oxygen water

2H2 + O2 2H2O

Hydrogen chloride + ammonia ammonium chloride

HCl + NH3 NH4Cl

Try this! Include:


#1: Potassium reacts with fluorine.


3. Decomposition- The splitting of one compound (reactant) into elements or smaller compounds- General format: AB A + B

Examples:2H2O2 2H2O + O2

Decomposition of hydrogen peroxide H2O2

Decomposition of water (hydrolysis)

Try this! Include:

- Word equation (if not already given)


- Balanced chemical equation- States of matter

#1: Mercury (II) oxide is heated.

Activity: Worksheet – Formation and Decomposition Reactions (pages 24-25)



4. Single Replacement- Also called single displacement- Involves one element and one compound as reactants- One element replaces (displaces) the other “like” element in the compound

o Metal element replaces the metal element in the compoundo Non-metal element replaces the non-metal element in the compound

- General format:

o Z + AB A + ZB (where Z and A are metals)

o Y + AB B + AY (where Y and B are non-metals)

Examples:2FeI2+Pb→PbI4+2Fe (metal replaces metal)

FeI2+Cl2→FeCl2+I2（non-metal replaces non-metal）


Try this! Include:


#1: Aluminum is added to a solution of sulfuric acid.

Activity: Worksheet – Single Replacement Reactions (page 28 and 29)




5. Double replacement- Also called double displacement- Like elements in different compounds replace (displace) each other

- General format: AB + XY AY + XBo Where A and X are metalso Where B and Y are non-metals

Examples:

HCl(aq)+ NaOH(aq)→NaCl(s)+H2O(l)

CaCO3(aq)+2HCl(aq)→CaCl2(s)+H2CO3(aq)

NOTE:


Neutralization reactions between acids and bases are double replacement reactions.

Johnny, finding life a bore,Drank some H2SO4.

Johnny's father, an MDGave him CaCO3.

Now he's neutralized it's true,But he's full of CO2.

Try this! Include:


#1: A solution of potassium phosphate reacts with cobalt (III) chloride

Activity: Worksheet –Double Replacement Reactions (page 32 and 33)



To Summarize:Science 1206 Unit 2: Chemical Reactions Page 32 of 38

AND:

Combustion

Activity: Worksheet –Predicting Chemical Reaction Type (page 35)


Science 1206Predicting Chemical Reaction Type

Instructions:

Classify each reaction as simple composition (sc), simple decomposition (sd), complete combustion (c), single replacement (sr), double replacement (dr) or other (o).

Classification1. Al(NO3)3(aq) + Na2CO3(aq) Al2(CO3)3(s) + NaNO3(aq) .

2. CaCO3(s) Ca(s) + C(s) + O2(g)

3. CH3OH(l) + O2(g) CO2(g) + H2O(g) .

4. BaO(s) + HOH(l) Ba(OH)2(s) .

5. F2(g) + MgCl2(aq) MgF2(aq) + Cl2(l) ,

6. H2O2(l) H2O + O2(g) .

7. C3H5(OH)3 + O2(g) CO2(g) + H2O(g) .

8. Ba(OH)2(aq) + HNO3(aq) HOH(l) + Ba(NO3)2(aq) .

9. C3H6 (g) + O2(g) CO2(g) + H2O(g) .

10. AgCl(s) Ag(s) + Cl2(g) .

11. Mg(s) + O2(g) MgO(s) .

12. Mg(s) + HCl(aq) MgCl2(aq) + H2(g) .

13. SrO(s) + CO2(g) SrCO3(s) .

14. Li(s) + O2(g) Li2O(s) .

15. Fe2O3(s) + HCl(aq) FeCl3(aq) + H2O(l) .

Unit 2: Chemical ReactionsScience 1206 Unit 2: Chemical Reactions Page 34 of 38

Notes: Part 6

Core Lab #6: Single Displacement and Double Displacement Reactions

TEXT: p. 242-245

Complete the worksheet and submit for grading.

YEAH! – No write-up!


Chemical Reactions and Energy

TEXT: p. 281 (exothermic and endothermic reactions)

Some chemical reactions seem to speed up as they progress

- A forest fire burns slowly at first and then may burn out of control.

What Happens:

- Temperature speeds up reactions rates because it increases the motion of particles which in turn increases the collisions between particles that result in a chemical change.

- That means that the heat energy released by the forest fire actually works to increase the rate of combustion.

Other reactions release energy (heat):

- Water freezing- Rubbing alcohol evaporating- Dynamite exploding

Chemical changes that release energy:

Exothermic

Chemical changes that require an input of energy:

Endothermic

Exothermic Reactions

Example: gasoline + oxygen carbon dioxide + water + heat energy

Some physical changes can be exothermic

Example: sulfuric acid (l) sulfuric acid (aq) + heat

(psst – always add acid to water)

An energy diagram can be used to graph the energy changes in an exothermic reaction.A + B -> C + D + Heat


Endothermic Reactions

Some reactions require heat energy on a continuous basis for the change to take place

- Heat can be absorbed from the surroundings- These changes do not speed up because surrounding temperature drops as heat is

absorbed.

Example: water (s) + heat energy water (l)

Energy diagram for an endothermic reaction

Heat + A + B -> C + D


Review

Chapter 5: p. 214-215 # 1 a) to d), 2 b) to f), 3 b) to h), 4, 5, 6, 7, 8, 9, 10, 11, 15

Chapter 6: # 1-10

Chapter 7: # 11

Chapter 8: 5, 6, 9, 16, 19

Unit 3 is CompleteFan-tab-u-lous!


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