Units 6 & 7

Question 1

evidence of a chemical reaction

Answer 1

color change

formation of a precipitate (solid)

formation of a gas (bubbles)

heat is produced (exothermic) or heat is absorbed (endothermic)

Question 2

chemical equation

Answer 2

Reactants → Products

Question 3

conservation of mass

Answer 3

In a chemical reaction, atoms are neither created nor destroyed

there must be the same number of atoms on the reactant side of the equation as there are on the product side of the equation

Question 4

physical states

Answer 4

g - gas

l - liquid

s - solid

aq - aqueous

Question 5

what causes reactions?

Answer 5

precipitation reactions (driving force = formation of precipitate)

gas-forming reactions (driving force = formation of a gas)

acid-base reaction (driving force = formation of water)

transfer of electrons

Question 6

precipitation

Answer 6

formation of a solid

solid formed = precipitate

reaction = precipitation reaction

Question 7

predicting precipitates

Answer 7

insoluble

solid

Question 8

strong electrolyte

Answer 8

a substance that completely breaks apart into ions when dissolved in water

resulting solution readily conducts an electric current

Ba(NO₃)₂ and K₂CrO₄

Question 9

soluble solid

Answer 9

readily dissolves in water

Question 10

insoluble solid

slightly soluble solid

Answer 10

only a small amount of the solid dissolves in water

Question 11

ionic compound

Answer 11

all salts

when ionic compounds dissolve, the resulting solution contains ions

Question 12

predicting equations

Answer 12

1. exchange anions & cations
2. balance charges
3. balance equation
4. use solubility rules to find precipitates

Question 13

combination

synthesis reaction

Answer 13

two reactants combine to form a single product. The reactants may be elements or compounds

Zn(s) + I₂(s) → ZnI₂(s)

Question 14

decomposition

Answer 14

one reactant, a compound, breaks down to give two or more products

2H₂O₂(aq) → 2H₂O(l) + O₂(g)

Question 15

single replacement

Answer 15

an element reacts with a compound and replaces one of the elements in the compound

Metals replace hydrogen or other metals; nonmetals replace nonmetals

Zn(s) + 2HCl(aq) → H₂(g) + ZnCl₂(aq)

Question 16

double replacement

Answer 16

2 ionic compounds exchange ions to form new compounds

NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq)

Question 17

combustion

Answer 17

a compound burns in the presence of oxygen, producing energy in the form of heat and light

the combustion of organic compounds produces carbon dioxide and water

C₄H₈(l) + 6O₂(g) → 4CO₂(g) + 4H₂O(g)

Question 18

molecular equation

Answer 18

shows the overall reaction but not necessarily the actual forms of the reactants & products in solutions

balanced in charge & molecules

K₂CrO₄(aq) + Ba(NO₃)₂(aq) → BaCrO₄(s) + 2KNO₃(aq)

Question 19

complete ionic equation

Answer 19

represents all reactants & products that are strong electrolytes as ions

all reactants & products are included

2K⁺(aq) + CrO₄^2-(aq) + Ba²⁺(aq) + 2NO₃^-(aq) → BaCrO₄(s) + 2K⁺(aq) + 2NO₃^-(aq)

when writing ions, put charge on top right, and change subscript to coefficient (unless polyatomic - in which case, MAKE SURE the subscript is EXTRA)

Question 20

spectator ions

Answer 20

ions that don’t participate directly in a reaction

Question 21

net ionic equation

Answer 21

includes only those components that undergo a change

spectator ions are not included

Ba²⁺(aq) + CrO₄^2-(aq) → BaCrO₄(s) [Ba²⁺ and CrO₄^2- both changed from aq to s]

Question 22

balancing tip

Answer 22

If two elements being combined have the same subscript, you can take it away and change it to a coefficient

Question 23

diatomic molecules

Answer 23

elements that exist as diatomic molecules in their elemental forms

HINClBrOF

H, I, N, Cl, Br, O, F