Science Chapter 19

Oxidation

Loss of electrons

Identify and describe the five general types of general reactions.

1. Combustion - Occurs when a substance reacts with oxygen to produce energy in the form of heat and light. (example: CO2) 2. Synthesis - Occurs when two or more substance combine to form another substance. Formula (pattern): A + B --> AB Example: H2(g) + Cl2(g) --> 2HCl(g) 3. Decomposition - Occurs when one substance breaks down, or decomposes, into two or more substances. Formula (pattern): AB --> A + B Example: 2H2O2(l) --> O2(g) + 2H2O(l) 4. Single Displacement: Occurs when one element replaces another element in a compound. Formula (pattern): A +BC --> AC + B Example: Cu(s) +2AgNO3(aq) --> Cu(NO3)2(aq) + 2Ag(s) 5. Double Displacement - Occurs when the positive ion of one compound replaces the positive ion of the other to form two new compounds. Formlua (pattern): AB +CD --> AD +CB Example: 2NaOH(aq) + CuCl2(aq) --> Cu(OH)2(s) + 2NaCl(aq)

compare and contract exergonic and endergonic reactions.

1. Exergonic reactions involve ionic bonds; endergonic reactions involve covalent bonds. 2. Exergonic reactions involve the breaking of bonds; endergonic reactions involve the formation of bonds. 3. Exergonic reactions involve the formation of bonds; endergonic reactions involve the breaking of bonds. 4. Exergonic reactions release energy; endergonic reactions absorb it. 5. In exergonic reactions, the reactants have less chemical energy than the products; in endergonic reactions, the opposite is true.

compare and contrast exothermic and endothermic reactions

1. an exothermic reaction requires continual supply of energy but an endothermic reaction does not 2. an exothermic reaction absorbs energy but an endothermic reaction releases energy 3. An exothermic reaction has energy as a product and an endothermic reaction has energy as a reactant 4. An exothermic reaction occurs best at high temperatures while an endothermic reaction occurs best at low temperatures.

equilibrium

is a state in which forward and reverse reactions or processes proceed at equal rates.

reaction rate

is the rate at which reactions change into products.

la Chatelier's priciple

states that if stress is applied to a system at equilibrium, the equilibrium shifts in the direction that opposes the stress. 1. changing concentration by adding or removing a reactant. 2. changing temperature by adding of removing heat 3. changing volume and pressure. (decrease volume increases the pressure)

Why are chemical reactions important?

A chemical reaction is a change in which one or more substances are converted into a new substance.

Identify how the source of energy changes in chemical reactions

All chemical reactions release or absorb energy. When chemical reactions take place, some chemical bonds in the reactants are broken, which requires energy called activation energy. In order for products to be produced, new bonds must be formed. Bond formation releases energy.

Redox reactions

Chemical reactions involving electron transfer of this sort often involve oxygen, which is very reactive, pulling electrons from metallic elements. The substance that gains an electron is reduced. The substance that loses electrons is oxidized. Reduction and oxidation always work as a pair. Example: Rust. Oxygen from the air pulls electrons from iron, iron becomes oxidized and therefore rusts

exergonic reaction

Chemical reactions that release energy are called exergonic reaction. (some sort of light or thermal energy is given off) ex: the abdomen of fire fly glows as a result of exergonic reaction

Reduction

Gain of electrons

How does a chemical reaction satisfy the law of conservation of mass?

The amount of mass on each side of the formula is equal, therefore satisfing the fact that mass is neither created nor destroyed.

endergonic reaction

When a chemical reaction requires more energy to break bonds than is released when new ones are formed. Ex: electric current passed through water produces hydrogen and oxygen

exothermic reaction

When the energy given off is primarily in the form of thermal energy is called exothermic reaction. ex: wood burning, explosion of dynamite, iron rusting

endothermic reaction

When the energy needed to keep a reaction going is in the form of thermal energy, the reaction is called endothermic reaction. ex: mixing Epsom salt with water. the solution becomes cold because it absorbs thermal energy. ex: adding baking soda to dough.

Distinguish how you can predict if a metal will replace another in a compound.

You can predict if a metal will replace another in a compound by looking at how active each metal is. The more active metal(s) will replace the less active metal(s).