Chapter 6 Notes Science 10 Name:

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6.1 Types of Chemical Reactions

a) Synthesis (A + B →→→→ AB) Synthesis reactions are also known as _________

reactions. When this occurs two or more reactants (usually

elements) join to form a _________.

A + B →→→→ AB, where A and B represent elements

The elements may form _________ compounds, like the following:

• Sodium metal and chlorine gas combine to form sodium chloride.

• 2Na + Cl2 → 2NaCl

• Magnesium metal reacts with oxygen gas to form magnesium oxide.

• 2Mg + O2 → 2MgO

Or the elements may form _________ compounds, like the following:

• Nitrogen gas and oxygen gas join to form dinitrogen monoxide.

• 2N2 + O2 → 2N2O Practice Problems

1. Complete and balance the following synthesis (combination) reactions. Remember to consider the chemical formulas of the products carefully before you begin to balance.

(a) ____Mg + ____N2 ➔ (b) ____Al + ____F² ➔ (c) ____K + ____O² ➔ (d) ____Cd + ____I2 ➔ (e) ____Cs + ____P4 ➔

2 2. Identify whether or not each of the following chemical equations is a synthesis (combination) reaction.

(a) 2H2 + O² ➔ 2H²O

(b) 2Al + 3CuCl2 ➔ 2AlCl³ + 3Cu (c) 2KClO3 ➔ 2KCl + 3O²

(d) S8 + 12O² ➔ 8SO³ (e) 2Ti + 3 Cl2 ➔ 2TiCl³

b) Decomposition (AB →→→→ A + B) Decomposition reactions are the _________ of synthesis reactions.

A compound _________

down into two or more products (often

elements).

AB →→→→ A + B where A and B represent elements

Ionic compounds may _________ to produce elements, like the following:

Table salt, sodium chloride, can be broken down into sodium metal and chlorine gas by _________ salt at 800ºC and running _________ through it.

• 2NaCl → 2Na + Cl2

Or covalent compounds may decompose into elements, like the following:

By running _________ through water, the water molecules _________ into hydrogen and oxygen gases.

2H²O → 2H2 + O2

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Practice Problems

1. Complete and balance the following decomposition reactions. Remember to check for diatomic elements as you write the formulas of the products.

(a) ____AuCl3 ➔ (b) ____K²O ➔ (c) ____MgF² ➔ (d) ____Ca3N2 ➔

(e) ____CsI ➔

2. Identify each reaction as synthesis, decomposition, or neither.

(a) CO2 ➔ C + O²

(b) 2AgCl + Cu ➔ CuCl² + 2Ag (c) 2Cr + 3F² ➔ 2CrF³

(d) CaI2 + Na²CO3 ➔ 2NaCl + CaCO³ (e) 2NaClO3 ➔ 2NaCl + 3O²

c) Single Replacement

Single replacement reactions replace one element from a compound with a separate element added as a reactant.

A compound and an element react, and the element switches places with part of the original compound.

 A + BC →→→→ B + AC where A is a _________, or

 A + BC →→→→ C + BA where A is a _____-metal

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When A is a metal:

Aluminum foil in a solution of copper(II) chloride produces solid copper and aluminum chloride.

2Al + 3CuCl² → 3Cu + 2AlCl3

When A is a non-metal:

When fluorine is bubbled through a sodium iodide solution, iodine and sodium fluoride are produced.

F² + 2NaI → I2 + 2NaF Practice Problems

1. Complete and balance the following single replacement reactions.

(a) ____PbCl4 + ____Al ➔ (b) ____Na + ____Cu2O ➔ (c) ____CuF2 + ____Mg ➔ (d) ____Cl2 + ____CsBr ➔ (e) ____Be + ____Fe(NO3)2➔

2. Classify each reaction as synthesis, decomposition, or single replacement.

(a) 2N²O ➔ 2N² + O²

(b) Au(NO3)3 + 3Ag ➔ Au + 3AgNO³ (c) CH4 ➔ C + 2H²

(d) 2NH4Br + Cl2 ➔ 2NH⁴Cl + Br2

(e) Br2 + I² ➔ 2IBr

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d) Double Replacement (AB + CD  AD + CB) 

Double replacement reactions _________ elements between two compounds reacting together to form two new compounds.

Two compounds react, with elements _________ places between the original compounds.

Two solutions react to form a _________ (ppt, solid) and another solution

 Ionic solution + ionic solution → ionic solution + ionic _________

 AB + CD →→→→ AD + CB

When potassium chromate and silver nitrate react, they form a red _________, silver chromate, in a _________ of potassium nitrate.

K²CrO₄ + 2AgNO₃ → Ag₂CrO₄ + 2KNO₃ Practice Problems

1. Complete and balance the following double replacement reactions. You do not need to decide which product(s) form a precipitate or to show states in the balanced equation.

(a) ____CaS + ____NaOH ➔ (b) ____K₃PO₄ + ____MgI₂➔ (c) ____SrCl2 + ____Pb(NO3)2➔ (d) ____AlCl3 + ____CuNO3➔

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(e) ____AgNO3 + ____Na2CrO4➔

2. Classify each reaction as synthesis, decomposition, single replacement, or double replacement.

(a) 2FeBr3 + 3Zn ➔ 3ZnBr² + 2Fe (b) FeBr₂ + ZnSO₄➔ ZnBr2 + FeSO₄ (c) 2Al + Fe₂O₃➔ 2Fe + Al2O₃ (d) 2Fe + O2➔ 2FeO

(e) 2FeBr3➔ 2Fe + 3Br²

e) Neutralization (Acid-Base Reactions)

Neutralization reactions occur when an acid (most compounds starting with H) and a _________ (most compounds ending in OH, or beginning with NH4) react to form a salt and _________.

• Acid + base → salt + water

• HX + MOH → MX + H2O where X and M are elements

• Sulfuric acid is used to neutralize calcium _________:

H²SO4 + Ca(OH) 2 → CaSO4 + 2H2O

• Phosphoric acid helps to neutralize the compounds that cause rust, such as iron(II) _________.

H³PO₄ + 3Fe(OH)₂ → Fe₃(PO₄)₂ + 6H₂O Practice Problems

1. Complete and balance the following neutralization (acid-base) reactions.

(a) ____HBr + ____NaOH  (b) ____H3PO4 + ____Mg(OH)2 (c) ____HCl +____Pb(OH)₂ (d) ____Al(OH)3 + ____HClO4

7 2. Classify each reaction as synthesis, decomposition, single replacement, double

replacement, or neutralization.

(a) 2HCl + Zn  ZnCl2 + H2

(b) 2HCl  H² + Cl2

(c) 2HCl + Sr(OH)2 SrCl² + 2H2O

(d) 2HCl + Pb(NO₂)₂ 2HNO2 + PbCl₂

f) Combustion

Combustion reactions occur when a compound or element reacts with ______

to release _________ and produce an _________.

• Also sometimes referred to as ___________combustion.

• CXHY + O2 → CO2 + H2O where X and Y represent integers

• Natural gas (_________) is burned in furnaces to heat homes.

CH⁴ + O2 → CO2 + 2H2O

• An acetylene torch is used to _________ metals together.

2C²H2 + 5O2 → 4CO2 + 2H2O

• Carbohydrates like glucose combine with oxygen in our body to release energy.

C⁶H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O Practice Problems

1. Complete and balance the following combustion reactions.

(a) C3H8 + O2➔ (b) C4H10 + O2➔ (c) C2H4 + O2➔

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(d) C6H12O6 + O2➔ (e) C12H22O11 + O2➔

2. Classify each reaction as synthesis, decomposition, single replacement, double replacement, neutralization, or combustion.

(a) 3Ca(NO³)² + 2Na³PO⁴ ➔ 6NaNO³ + Ca³(PO⁴)² (b) Ca(OH)² + H²SO⁴ ➔ 2H²O + CaSO⁴

(c) 2C⁶H⁶ + 15O² ➔ 12CO² + 6H²O (d) 6Mg + P4 ➔ 2Mg³P2

(e) C2H6O + 3O2 ➔ 2CO² + 3H²O

Summary of Types of Chemical Reactions

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Practice Problems

For each of the following reactions, classify the reaction type and then predict what the products will be.

Then write the skeleton equation and balance it.

1. ____Fe₂O₃ ➔

2. ____Al + ____NiBr₃ ➔ 3. ____Cl2 +____NiBr2 ➔ 4. ____HCl + ____Mg(OH)2 ➔ 5. ____C18H38 + ____O2 ➔ 6. ____Li + ____N2 ➔

7. ____AgNO3 + ____Na2CrO4 ➔

6.2 Factors Affecting the Rate of Chemical Reactions

Often, controlling the rate of a chemical reaction is as important as having the reaction occur in the first place. Altering certain factors can determine the _____

at which a chemical reaction occurs.

• To make a reaction happen quickly:

Increase the _________ where the reaction occurs.

Increase the _________ of reactants.

Increase the amount of _________ area that reacts.

Add a _________ or remove an _________.

• To make a reaction happen slowly:

_________ the temperature where the reaction occurs.

_________ the concentration of reactants.

_________ the amount of surface area that reacts.

_________ a catalyst or _________ an inhibitor.

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a) Temperature

• Temperature is the _________ energy of molecules.

The more energy molecules have, the higher the temperature.

When molecules have more energy, they _________ around more, _________ into other molecules more, and therefore react _________.

• The rate of reaction changes with the temperature.

Higher temperature = _________ reaction rate, and vice versa.

Sometimes we want slower reactions (we use a _________ to prevent spoilage).

Sometimes we want faster reactions (we _________ food to speed up the production of new molecules).

Learning Check (p. 272-274)

1. Heating a light stick can make it glow brighter. Why?

The brighter light of a hot glow stick is due to a faster reaction rate caused by heating.

2. What happens to the rate of a chemical reaction when the temperature is raised?

Raising the temperature of a chemical reaction increases the reaction rate.

3. What does cooling do to the frequency at which particles of reactants can collide?

Cooling decreases the frequency at which particles of reactants can collide.

4. How does cooling affect the energy of the collisions between particles?

Cooling lowers the energy of the collisions between reactant particles.

b) Concentration

Concentration refers to how many molecules of a substance exist in a certain _________.

• Concentration is how much _________ is dissolved in _________.

• Concentration is measured in mass per unit volume (g/L).

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• Usually, the higher the concentration of reactants, the faster the reaction occurs.

Since there are _________ molecules per unit volume in high

concentrations, there are more __________________ for molecules to collide and react.

A splint of wood glows brighter in highly _____________ oxygen than in normal _________ with a lower concentration of oxygen.

c) Surface Area

Chemical reactions occur when and where atoms and compounds collide.

Therefore, the more atoms and molecules there are to collide, the higher the reaction rate.

• Increasing surface area _________ the rate of reaction.

• Surface area can be increased by creating _________ pieces.

• A _________ substance has far more surface area than one large _________.

• The increase in surface area must also be exposed for reaction; a powder only reacts more quickly if it is in contact with the other reactant(s).

Reading Check (p. p. 275-276)

1. How does increasing concentration result in an increase in reaction rate?

2. Can the concentration of a substance change if it is a gas?

3. Can the concentration of a solution change if it is an aqueous solution?

12 4. How does increasing the surface area of a reactant increase reaction rate?

d) Catalysts

Sometimes, increasing the temperature or concentration is not a desirable method to increase reaction rate. Changing these two variables may be impractical or dangerous. An alternate technique is to use a catalyst. A catalyst is a chemical that allows a reaction to occur more _________ without actually participating in the reaction itself.

• The catalyst speeds up the reaction rate but does not get _________ up as a reactant.

• Catalysts often _________ the amount of energy necessary to break the bonds in the reactants.

• _________ are an example of biological catalysts.

• Saliva has enzymes that help speed the breakdown of _________ when they enter the mouth.

• A catalytic converter is a device installed in cars to _________ _________.

Car exhaust passes through the catalytic converter before leaving the car.

Catalysts found in the honeycomb-shaped filters in the converter help to change many of the pollutants into _________ _________ substances.

 _________ carbon monoxide is changed into CO².

 Hydrocarbons are converted into CO² and _________.

 Nitrogen oxides are changed into _________ and _________.

• 2N2O₃ → 2N₂ + 3O₂

Non-metal oxide