Unit 6: Chemical reaction test study guide

reactant

A substance that participates in a chemical reaction.

product

A substance that forms in a chemical reaction.

Activation Energy

The minimum amount of energy required for a chemical reaction to occur.

Diatomic Element

Refers to an element that naturally exists as molecules consisting of two atoms of the same element bonded together.

(s)

solid element

(l)

liquid element

(g)

gas element

(aq)

dissolved in water

Synthesis

two simpler substances combine to make a more complex substance (1 product).

decomposition

A complex substance decomposes to form simpler substances.

single displacement

One element displaces another in a compound.

double displacement

Two elements/groups of elements in two different compounds exchange places to form two new compounds.

incomplete combustion

Reactions always form water and carbon monoxide.

complete combustion

Reactions always form water and carbon dioxide.

precipitate

A solid that forms and separates from a liquid solution during a chemical reaction.

coefficient

A number that shows the relative amount of a compound in a reaction.

catalyst

A substance that speeds up or slows down a reaction but is NOT changed in the process and is not used up.

Reaction Rate

The speed at which a chemical reaction proceeds.

exothermic

Reactions that RELEASE energy.

Endothermic

Reactions that ABSORB energy

observations that show a chemical reaction

grow, ripen, decay, burn, breathe, digest

Evidence of a chemical reaction

formation of gas, formation of a solid (precipitate), formation of an oder, release of energy (in the form of heat or light)

Why mist we balance chemical equations by adding coefficients?

* Balanced chemical equations account for the law of conservation of mass: "matter cannot be created or destroyed."
* When the numbers of atoms for EACH element on the reactant side AND product side are equal, the equation is balanced.

Catalyst

* speeds up the rate of a reaction
* provides an alternative reaction pathway to lower the activation energy, making it easier for the reaction to occur

inhibitor

* not consumed in the reaction, but can be reused multiple times.
* slows down or reduces the rate of a reaction
* Can interfere with reactants, catalyst, or reaction pathway itself, increasing the activation energy or reducing the efficiency of the reaction.
* Prevent/hinder the reaction from occurring efficiently.

What is chemical equilibrium?

Balance that is reached by two opposing forces; when to forward and reverse rates of reaction are equal.

What types of reaction obtain chemical equilibrium?

Reactions with the double arrows (reversible reactions, phase changes, dissolution, gas-phase reactions, etc.)

How can we tell if a chemical equilibrium has be reached?

Equilibrium has been reached when the rate of the forward reaction is equal to the rate of the reverse reaction.

Concentration (affect chemical equilibrium)

Changes in concentration of reactants/products shift equilibrium toward the side that counteracts the change.

Temperature (affect chemical equilibrium)

An increase in temperature shifts the equilibrium toward the endothermic side, and a decrease shifts it toward the exothermic side.

Pressure (affect chemical equilibrium)

Increasing pressure shifts the equilibrium toward the side with fewer gas molecules; decreasing pressure shifts it toward the side with more gas molecules.

volume (affect chemical equilibrium)

Changing volume (which affects pressure) can shift the equilibrium in the same way as pressure.

Catalysts (affect chemical equilibrium)

Speed up approach to equilibrium but do not affect the equilibrium position.

Inert Gases (affect chemical equilibrium)

Do not affect equilibrium unless volume is changed.