ch. 8 - chemical equations and reactions

Question 1

chemical reaction

Answer 1

process by which one or more substances are changed into one or more different substances

Question 2

law of conservation of mass

Answer 2

the total mass of reactants must equal the total mass of products for any given chemical equation

Question 3

chemical equation

Answer 3

representing, with symbols and formulas, the identities and relative molecular or molar amounts of the reactants and products in a chemical reaction

Question 4

indication of a chemical reaction

Answer 4

• evolution of energy as head or light
• production of gas/odor
• formation of a precipitate

Question 5

an equation gives no indication of…

Answer 5

• whether a reaction will actually occur
• the speed at which it will occur
• how the bonding between atoms or ions change during reactions

Question 6

synthesis reaction

Answer 6

two or more substances combining to form ONE new compound

A + X –> AX

Question 7

decomposition

Answer 7

a single compound undergoes a reaction to produce two or more simpler substances
AX –> A +X OR AB + O –> AO + BO

Question 8

electrolysis

Answer 8

decomposition of substances by an electric current

Question 9

single displacement (/replacement)

Answer 9

one element replaces a similar element in a compound
A + BX –> AX + B OR Y + BX –> BY + X
- many take place in aqueous solutions

• metal = A + BX –> AX + B (replaces first one)
• nonmetal = Y + BX –> BY + X (replaces second one)

Question 10

combustion

Answer 10

a substance combines with oxygen, releasing a large amount of energy in the form of light and heat
- the combustion of ANY hydrocarbon (consisting of hydrogen and carbon) and oxygen ALWAYS yields CO2 and H2O

Question 11

up arrow

Answer 11

gas forms

Question 12

down arrow

Answer 12

precipitate forms

Question 13

–> with triangle on top

Answer 13

heat applied

Question 14

two opposite facing arrows in the form of an equal sign

Answer 14

reversible action

Question 15

aq

Answer 15

aqueous – dissolved in water

Question 16

activity

Answer 16

the ability of an element to react

- the more readily an element reacts with other substances, the greater its activity is

Question 17

activity series

Answer 17

a list of elements organized according to the ease with which they undergo certain chemical reactions

• metals: greater activity means it loses electrons easier to form positive ions
• nonmetals: greater activity means it gains electrons easier to form negative ions

Question 18

precipitate

Answer 18

a solid produced as a result of a chemical reaction that separates from the solution
- in a solution with two aqueous reactants, if one of the products is a solid, it is a precipitate!