Chemistry Unit 11 Flashcards

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Questions and Answers

How do you write a skeleton equation?

To write a skeleton equation, write the chemical formulas for the reactants to the left of the yields sign (arrow) and the formulas for the products to the right.

Chemists use a chemical equation to

convey as much information as possible about what happens in a chemical reaction.

How do you describe what happens in a chemical reaction?

The reactants are written on the left and the products on the right. An arrow separates them. You read the arrow as yields, gives, or reacts to produce.

How could you describe the rusting of iron?

You could say, 'Iron reacts with oxygen to produce iron(III) oxide (rust).' Signup and view all the answers

The production of a new substance, a gas, is evidence of

a chemical change. Signup and view all the answers

The burning of methane is a ________ reaction.

chemical Signup and view all the answers

What do word equations write?

write the names of the reactants to the left of the arrow, separated by plus signs. Write the names of the products to the right of the arrow, also separated by plus signs. Signup and view all the answers

What is a chemical equation?

A representation of a chemical reaction; the formulas of the reactants (on the left) are connected by an arrow with the formulas of the products (on the right). Signup and view all the answers

What is a skeleton equation?

A chemical equation that does not indicate the relative amounts of the reactants and products. Signup and view all the answers

How can you indicate the physical states of substances in an equation?

by putting a symbol after each formula. Signup and view all the answers

What is a catalyst?

A substance that speeds up the reaction but is not used up in the reaction. Signup and view all the answers

Where is a catalyst written in a chemical equation?

above the arrow in a chemical equation. Signup and view all the answers

What are the advantages of using a chemical equation?

A chemical equation for a reaction is easier to read quickly and shows all the relevant information. Signup and view all the answers

What are the steps for writing and balancing a chemical equation?

<ol> <li>Write the skeleton equation. 2. Use coefficients to balance the equation. 3. Check each atom or polyatomic ion for equality on both sides.</li> </ol> Signup and view all the answers

What is a balanced equation?

A chemical reaction described by a balanced equation in which each side has the same number of atoms and mass is conserved. Signup and view all the answers

What are the five general types of reactions?

combination, decomposition, single-replacement, double-replacement, and combustion. Signup and view all the answers

By classifying chemical reactions, you can more easily predict

what products are likely to form. Signup and view all the answers

Not all chemical reactions fit uniquely into

one category. Signup and view all the answers

What is a combination reaction?

(AKA synthesis) a chemical change in which two or more substances react to form a single new substance. Signup and view all the answers

What is a decomposition reaction?

A chemical change in which a single compound breaks down into two or more simpler products. Signup and view all the answers

What happens in a decomposition reaction when a vehicle's air bag inflates?

Sodium azide pellets decompose and release nitrogen gas, quickly inflating the air bag. Signup and view all the answers

Provide an example of a decomposition reaction.

2HgO(s) → 2Hg(l) + O2(g) Signup and view all the answers

What are diatomic molecules?

hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, and iodine. Signup and view all the answers

What is a single-replacement reaction?

One in which one element replaces a second element in a compound. Signup and view all the answers

Provide an example of a single-replacement reaction.

2K(s) + 2H2O(l) → 2KOH(aq) + H2 Signup and view all the answers

Whether one metal will displace another metal from a compound depends upon

the relative reactivities of the two metals. Signup and view all the answers

What is an activity series of metals?

Lists metals in order of decreasing reactivity. Signup and view all the answers

A halogen can also replace another _______ from a compound.

halogen Signup and view all the answers

The activity of halogens _________ as you go down Group 7A of the periodic table.

decreases Signup and view all the answers

What is a double-replacement reaction?

A chemical change involving an exchange of positive ions between two compounds. Signup and view all the answers

Provide an example of a double-replacement reaction.

2KI(aq) + Pb(NO3)2(aq) → PbI2 + 2KNO3(aq) Signup and view all the answers

What is a combustion reaction?

A chemical change in which an element or compound reacts with oxygen, often producing energy in the form of heat and light. Signup and view all the answers

What does the complete combustion of a hydrocarbon produce?

carbon dioxide and water. Signup and view all the answers

What does the complete combustion of a hydrocarbon release?

a large amount of energy as heat. Signup and view all the answers

Why might you want to classify a chemical reaction?

Classifying a chemical reaction helps you predict what products will form. Signup and view all the answers

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Study Notes

Skeleton Equations and Chemical Reactions

Skeleton equations represent chemical reactions, with reactants on the left and products on the right of the yields sign (→).
Chemical equations convey essential information regarding the nature of a chemical reaction.

Describing Chemical Reactions

Reactants are read as yielding products; the notation used is Reactants → Products.
Example: Iron + Oxygen → Iron(III) Oxide describes rusting.

Evidence of Chemical Change

Production of a gas signifies a chemical change, e.g., hydrogen peroxide decomposes into water and oxygen gas.

Types of Chemical Reactions

Combustion of methane requires oxygen and produces carbon dioxide and water.
Five general types of reactions: combination, decomposition, single-replacement, double-replacement, and combustion.

Writing Chemical Equations

Word equations list reactant names separated by plus signs on the left and product names on the right.
Balanced equations adhere to the law of conservation of mass, with equal atom counts on both sides.

Balancing Chemical Equations

Using coefficients ensures the number of each type of atom is the same on both sides.
Steps include writing the skeleton equation, counting atoms, balancing with coefficients, and verifying all diatomic molecules.

Types of Specific Reactions

Combination Reaction: Two or more substances form a single new substance.
Decomposition Reaction: A single compound breaks down into two or more simpler products, generally requiring energy.
Example: Sodium azide in airbag triggers nitrogen gas release.

Reactivity Series

In single-replacement reactions, one element displaces another based on their relative reactivities.
The activity series ranks metals by reactivity.

Double-Replacement Reactions

Involve an exchange of ions between two compounds, commonly in aqueous solutions leading to precipitate formation.
Example: KI + Pb(NO3)2 → PbI2 + 2KNO3 illustrates this process.

Combustion Reactions

Typically involve hydrocarbons reacting with oxygen to release carbon dioxide, water, and energy.
Incomplete combustion can yield carbon or carbon monoxide if oxygen supply is restricted.

Importance of Classification

Classifying reactions aids in predicting potential products and understanding reaction behavior.

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