Chapter 4: Types of Chemical Reactions and Solution Stoichiometry

Question 1

Define: solution

Answer 1

a combination of two or more substances that exist as a homogeneous mixture

Question 2

Define: solvent

Answer 2

the substance present in the greatest quantity in a solution

Question 3

Define: solute

Answer 3

the substance of lesser quantity in a solution

Question 4

Define: solubility

Answer 4

a measure of the amount of substance that will dissolve in a given amount of solvent at a given temperature

Question 5

Define: aqueous solution

Answer 5

solution in which water is the solvent

Question 6

Define: concentration

Answer 6

amount of solute / volume of solution

Question 7

Define: molarity

Answer 7

moles of solute/ litres of solution

Question 8

Fill in the blank: when ionic solids (salts) are dissolved in polar solvents such as H2O, they _________

Answer 8

dissociate into anions and cations

Question 9

Water can dissolve non-ionic compounds as long as?

Answer 9

they are polar (remember: like dissolves like)

Question 10

Give some evidence for a (possible) chemical reaction (5)

Answer 10

–  formation of a precipitate (an insoluble solid) 
–  formation of a gas
–  change in colour
–  change in temperature
–  dissolution of a precipitate

Question 11

Define: precipitation reactions

Answer 11

reactions of two soluble ionic compounds that yield an insoluble product (precipitate)

Question 12

not all ionic compounds are soluble in H2O, but those that are _____________

Answer 12

completely dissociate

Question 13

Fill in the blank: ionic solids that precipitate out of solution must be ______________

Answer 13

electrically neutral

Question 14

List the solubility rules

Answer 14

• Group 1 elements are soluble
• ammonium (NH4+ ), acetate (C2H3O2-), nitrate (NO3-)
• chlorides, bromides, and iodides are soluble except with Ag+, Pb2+, Hg22+
• sulfates are soluble except with Ca2+, Sr2+, Ba2+, Pb2+

Question 15

Define: molecular equation

Answer 15

A molecular equation is an equation in which the formulas of the compounds are written as though all substances exist as molecules.

AgNO3(aq) + KI(aq) → AgI(s) + KNO3(aq)

Question 16

Define: complete ionic equation

Answer 16

breaking all the soluble ionic compounds (those marked with an (aq)) into their respective ions

Ag+(aq) + NO3-(aq) + K+(aq) + I -(aq) → AgI(s) + K+(aq) + NO3-(aq)

Question 17

Define: net ionic equation

Answer 17

A net ionic equation shows only the chemical species that are involved in a reaction

Ag+(aq) + I -(aq) → AgI(s)

Question 18

Define: Selective Precipitation

Answer 18

• process used for qualitative analysis where mixtures of ions are separated by performing a series of reactions and precipitating the ions one at a time

Question 19

Define: tailing ponds

Answer 19

• reservoirs that are lined with plastics and concrete so water does not leech out.
• wastes from mining ends up in tailing ponds
• water is full of heavy and toxic metals
• example: arsenic sludge is poured into pond
• water slowly evaporates overtime and they can extract the arsenic out

Question 20

Define: arrhenius concept

Answer 20

in water, acids produce hydrogen ions and bases produce hydroxide ions

Question 21

What is another name for acid and base?

Answer 21

acid: proton donor
base: proton acceptor

Question 22

What are the reactants and products of a neutralization reaction?

Answer 22

reactants: strong base and strong acid
products: salt and water

Question 23

Describe acid-base titrations

Answer 23

• Use acid-base titrations to determine, for example, the amount of acid in an unknown sample
• Usually a controlled reaction of adding base (the titrant) of known concentration to the acid. The point in the titration at which enough titrant has been added to react completely with the unknown acid is called the equivalence point or stoichiometric point
• Acid base titrations require the use of an indicator. Indicator: a different color when it is in an acidic solution compared to when it is in a basic solution. commonly it is phenolphthalein

Question 24

Define: Oxidation-reduction reactions (Redox reactions)

Answer 24

a reaction in which one or more electrons are transferred between atoms or molecules

Question 25

Half reactions

Answer 25

2 Na(s) → 2 Na+ + 2e-

Cl2(g) + 2e- → 2 Cl-

Question 26

Define: oxidation and reduction

Answer 26

oxidation: electrons lost
reduction: electrons gained

Question 27

Define: oxidizing agent

Answer 27

gains electrons (i.e., is reduced) in order to oxidize a compound or ion

Question 28

Define: reducing agent

Answer 28

loses electrons (i.e., is oxidized) in order to reduce a compound or ion

Question 29

Define: strong electrolytes and give examples

Answer 29

• substances that are (essentially) completely ionized in aqueous solution
• soluble salts, strong acids, strong bases

Question 30

Define: weak electrolytes and give examples

Answer 30

• substances that only partially ionize in solution
• weak acids
• weak bases

Question 31

Define: non-electrolytes

Answer 31

substances (molecular compounds) that are soluble but do not ionize

Question 32

Differentiate between monoproctic acids vs polyprotic acids

Answer 32

• monoprotic acids: acids with 1 hydrogen atom to give off when dissolved in a solute
• polyproctic acids: have more than 1 acidic hydrogen