Chemistry Chapter 10 (copy)

What is the core concept of this chapter?

• Chemical symbols, formulas, and equations can be used to concisely represent elements, compounds, and what happens in a chemical reaction

What are the different types of chemical formulas?

• Empircal formula, Molecular Formula, and Structural Formula

  • Empircal Formula - identifies the elements present in terms of simplest whole # ratios

    • ex. CH2O

  • Molecular Formula - Identifies actual number of atoms in a molecular compound

    • ex. C6H12O6

  • Structural Formula - Represents arracngement of atoms within a molecule; related to 3-D structures of molecules

    • ex. ⬇

      

Empiral vs. Molecular Formula?

Empircal: Ionic-lacking discrete unit, or molecule, composed of both metallic and nonmetallic elements, electronegativty difference 71.7

ex. CH20

Molecular: Covalent compounds, usually nonmetals bound to nonmetals, molecular and empirical formulas can be different

ex. C6H12O6

Molecular and Formula Mass

Formula mass - sum of all atomic masses of all atoms in chemical formula

Molecular mass - Formula mass of a molecular substance; often used for nonmolecular substances as well

Chemical Reactions

• Those that give off energy are exothermic

  • ex. engine, fire, handwarmers, combustion, bombs

• Those that take in energy are endothermic

  • ex. cold pack, cooking a steak, frying eggs, photosynthesis

• Some reactions need an energy boos to get the reaction started, this is called activation energy

  • ex. match, flint, sparking

Types of Chemical Reactions
1) Synthesis reaction: combining reactants to form a new compound

• ex. A + B → AB

2) Decomposition Reaction: Breaking a compound into smaller parts

• ex. AB → A + B

3) Single Displacement: 1 element and 1 compound react to form a different element and a different compound

• ex. A + BC → AC + B

4) Double Displacement: The components of two compounds change places. A precipitate is formed

• ex. AB + CD → AD + CB

Oxidation-Reduction Reaction

• Oxidation - loss of electrons

• Reduction - gain of electrons

Ion Exchange Reaction

• A reaction that takes place when the ions of one compound interact with the ions of another compound forming: a solid precipitate, a gas, and water

  • ex. AX + BY → AY + BX

Balancing Chemical Equations

Law of Conversation of Mass - Matter is neither created nor destroyed during a chemical reaction

• To balance a chemical equation, you have to make sure that the atoms present at one side of a reaction are also displayed on the other side of the reaction

Chemical Equations (Word)

• What is this chemical equation in word form?

  • CA + 2H20 → Ca(OH)2 + H2

    • Answer: One molecule of calcium plus two molecules of water yields one molecule of calcium hydroxide plus one molecule of hydrogen gas

• What is this chemical equation in number form?

  • Two molecules of hydrogen gas plus one molecule of oxygen gas yields two molecules of water.

    • Answer: 2H2 + O2 → 2H20

Ch.10 Formula Mass

Formula Mass - The sum of the atomic masses of the elements in a chemical formula

Moles

Important concepts of the mole

• Recall that the atomic weight of elements are average relative masses of the isotopes of the element. Everything is compared to Carbon-12

• Carbon-12 has exactly 6.02 × 10(23) atoms. This is Avogardo’s number.

• Avogardo said that equal volumes of gases contain equal number of molecules.

• An amount of a substance that contains Avogardo’s number of atoms, ions, or molecules is defined as a mole of that substance