HC CH 11 sec 1 - Eastern Regional High Schoolweb.eccrsd.us/borda/public/honors/HC_CH11_1.pdf · 2/5/14 2 11.1 Chemical Reactions > 5 Copyright © Pearson Education, Inc., or its affiliates

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11.1 Chemical Reactions >

1 Copyright © Pearson Education, Inc., or its affiliates. All Rights Reserved.

Chapter 11 Matter and Change 11.1 Describing Chemical

Reactions 11.2 Types of Chemical Reactions 11.3 Reactions in Aqueous Solution



Introduction to Chemical Equations

•  Reactants written on the left.

•  Products on the right.

•  Read the arrow as yields, gives, or reacts to produce.

Reactants → products

Word Equations




•  You could say, “Iron reacts with oxygen to produce iron(III) oxide (rust).”

Word Equations

Iron + oxygen → iron(III) oxide

Fe + O2 → Fe2O3

•  A skeleton equation is a chemical equation that does not indicate the relative amounts of the reactants and products.



Chemical Equations


States of matter •  Use (s) for a solid, (l) for a liquid, (g) for a

gas, and (aq) for a substance in an aqueous solution (a substance dissolved in water).

Fe(s) + O2(g) → Fe2O3(s)

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Word Equations

Hydrogen peroxide → water + oxygen

•  “Hydrogen peroxide decomposes to form water and oxygen gas.”



Chemical Equations


•  A catalyst is a substance that speeds up the reaction but is not used up in the reaction.

•  A catalyst is neither a reactant nor a product, so its formula is written above the arrow in a chemical equation.

H2O2(aq) H2O(l) + O2(g) MnO2



Interpret Data

Symbols Used in Chemical Equations

Symbol Explanation

+ Separates two reactants or two products

→ “Yields,” separates reactants from products

Use in place of → for reversible reactions

(s), (l), (g) Designates a reactant or product in the solid state, liquid state, or gaseous state; placed after the formula

(aq) Designates an aqueous solution; the substance is dissolved in water; placed after the formula

Indicates that heat is supplied to the reaction

A formula written above or below the yields sign indicates its use as a catalyst (in this example, platinum).

Δ

heat

Pt



Hydrochloric acid reacts with solid sodium hydrogen carbonate. The products formed are aqueous sodium chloride, water, and carbon dioxide gas. Write a skeleton equation for this chemical reaction.

Sample Problem 11.1

Writing a Skeleton Equation

NaHCO3(s) + HCl(aq) → NaCl(aq) + H2O(l) + CO2(g)

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Balancing Chemical Equations


In a balanced equation each side of the equation has the same number of atoms of each element. •  Bonds holding the reactants together are broken,

new bonds are formed.

•  The atoms themselves are neither created nor destroyed; they are merely rearranged.

•  Mass is conserved.




First write the skeleton equation.

Then use coefficients to balance the equation so that it obeys the law of conservation of mass.



C(s) Carbon

+ O2(g) Oxygen

CO2(g) Carbon dioxide

Reactants 1 carbon atom, 2 oxygen atoms

Product 1 carbon atom, 2 oxygen atoms


Carbon burns in the presence of oxygen to produce carbon dioxide.

•  This equation is balanced.

•  You do not need to change the coefficients. –  They are all understood to be 1.




When hydrogen and oxygen are mixed, the product is water.

•  The formulas for all the reactants and the product are correct, but this equation is not balanced. –  As written, the equation does not obey the law of

conservation of mass.

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•  If you put the coefficient 2 in front of H2O, oxygen will be balanced.





•  To correct this equation, put the coefficient 2 in front of H2.



The reaction between oxygen and hydrogen in fuel cells produces the energy to power a car. What are the products of the reaction in a fuel cell that make the fuel-cell car a zero-emission car?

CHEMISTRY & YOU 11.1 Chemical Reactions >


The reaction between oxygen and hydrogen in fuel cells produces the energy to power a car. What are the products of the reaction in a fuel cell that make the fuel-cell car a zero-emission car? Water is the product of the reaction between oxygen and hydrogen in a fuel cell. Water is not a pollutant, and so fuel-cell cars are considered “zero-emission” cars.

CHEMISTRY & YOU

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Students suspended copper wire in an aqueous solution of silver nitrate. They noticed a deposit of silver crystals on the copper wire when the copper reacted with the silver nitrate. They recorded the equation for this reaction but didn’t balance it. Write an equation and balance it.

AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + Ag(s)

Sample Problem 11.2

Balancing a Chemical Equation



Sample Problem 11.2

2AgNO3(aq) + Cu(s) → Cu(NO3)2(aq) + 2Ag(s)



Aluminum is a good choice for outdoor furniture because it reacts with oxygen in the air to form a thin protective coat of aluminum oxide. Balance the equation for this reaction.

Sample Problem 11.3

Balancing a Chemical Equation

Al(s) + O2(s) → Al2O3(s)



Sample Problem 11.3

2Al(s) + O2(s) → 2Al2O3(s)

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Sample Problem 11.3

2Al(s) + 3O2(s) → 2Al2O3(s)



Sample Problem 11.3

4Al(s) + 3O2(s) → 2Al2O3(s)

Final



Balance the following equation.

C3H8(g) + O2(g) → CO2(g) + H2O(l)



Balance the following equation.

C3H8(g) + O2(g) → CO2(g) + H2O(l)

C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)

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HC CH 11 sec 1 - Eastern Regional High Schoolweb.eccrsd.us/borda/public/honors/HC_CH11_1.pdf · 2/5/14 2 11.1 Chemical Reactions > 5 Copyright © Pearson Education, Inc., or its affiliates