5. Chemical Reactions

Question 1

Chemical reaction/ change

Answer 1

-one or more reactants are converted into one or more products

Question 2

Formula weight

Answer 2

-sum of the atomic weights in atomic mass units (amu) of all atoms in the compound’s formula
-used for both ionic and covalent compounds

Question 3

Molecular weight

Answer 3

-term strictly used for covalent compounds

Question 4

Mole (mol)

Answer 4

-the formula weight of a substance expressed in grams
-formal definition: the amount of substance rhat contains as many atoms/molecules/ions as there are atoms in exactly 12g of C-12

Question 5

Avogadro’s number (#23 sa calcu)

Answer 5

-6.02 x 10^(23) formula units per mole
-the amount of any substance that contains as many formula units as the number of atoms in 12 g of C-12

•Amadeo Avogadro
-proposed the concept of mole, but was not able to determine the number experimentally

Question 6

Molar mass

Answer 6

-the mass of one mole of a substance expressed in grams
-formula weight of a compound expressed in grams

Question 7

Combustion

Answer 7

-burning in air

Question 8

Chemical equation

Answer 8

-a representation using chemical formulas of the process that occurs when reactants are converted to products
-written with the coefficients expressed as the lowest set of whole numbers

Question 9

Stoichiometry

Answer 9

-the mass relationships in a chemical reaction
-from Greek “stoicheion” meaning element & “metron” meaning measure

Question 10

Limiting reagent

Answer 10

-the reactant that is used up first
-the reactant that is consumed, leaving an excess of another reagents or reagents unreacted

Question 11

Percent yield

Answer 11

-actual yield divided by the theoretical yield times 100

Question 12

Actual yield

Answer 12

-the mass of product formed in a chemical reaction

Question 13

Theoretical yield

Answer 13

-mass of product that should form in chemical reaction according to the stoichiometry of the balanced equation
-maximum yield

Question 14

Aqueous solution

Answer 14

A solution in which the solvent is water

Question 15

Dissociation

Answer 15

When ionic compound dissolve in water, cation and anions become separated from each other by water molecules

Question 16

Spectator ion

Answer 16

-Ion that appears unchanged on both sides of a chemical equation
-did not participate in the reaction

Question 17

Net ionic equation

Answer 17

A chemical equation that does not contain spectator ions; shows only species that actually take part in the reaction

Question 18

Ions in solution react with each other only when one of these four things can happen:

Answer 18

1. Two ions form a solid that is insoluble in water (i.e. AgCl)
2. Two ions form a gas that escapes from the reaction mixture as bubbles. (i.e. NaHCO3 with HCl to form CO2)
3. An acid neutralize a base
4. One of the ions can oxidize another

Question 19

Solubilities of ionic compounds:
Useful generalizations

Answer 19

1. All compounds containing Na+, K+, NH4+ ions are soluble in water.
2. All nitrates (NO3-) and acetates (CH3COO-) are soluble in water.
3. Most chloride (Cl-) and sulfates (SO4^(-2)) are soluble in water.
   •Exceptions (insoluble in water): silver chloride (AgCl), lead (II) chloride (PbCl2), mercury (I) chloride (Hg2Cl2), barium sulfate (BaSO4), and lead sulfate (PbSO4)
4. Most carbonates (CO3^(-2)), phosphates (PO4^(-3)), sulfides (S(-2)), and hydroxides (OH-) are insoluble in water.
   •Exceptions (soluble in water): LiOH, NaOH, KOH, aqueous NH3.

Question 20

Oxidation

Answer 20

-loss of electrons; gain of oxygen atoms or the loss of hydrogen atoms

Question 21

Reduction

Answer 21

-gain of electrons; loss of oxygen atoms or the gain of hydrogen atoms

Question 22

Oxidation-reduction reaction

Answer 22

-involves transfer of electrons from one species to another

Question 23

Oxidizing agent

Answer 23

-an entity that accepts electrons in redox reaction

Question 24

Reducing agent

Answer 24

-entity that donates electrons in redox reaction

Question 25

Redox reactions that are extremely common:
1. Combustion

Answer 25

-compounds or mixtures that are burned are oxidized by oxygen, O2

Question 26

Redox reactions that are extremely common:
2. Respiration

Answer 26

-the oxygen in the air we breathe oxidizes carbon-containing compounds in our cells to produce CO2 and H2O

-same lang sa combustion, but at slower and occurs at lower temperature

Question 27

Redox reactions that are extremely common:
3. Rusting

Answer 27

-iron is oxidized to a mixture of iron oxides

Question 28

Redox reactions that are extremely common:
4. Bleaching

Answer 28

-common bleaches are oxidizing agents
-colored compounds being bleach are usually organic compounds; oxidation converts them to colorless compounds

Question 29

Redox reactions that are extremely common:
5. Batteries

Answer 29

-voltaic cells is a device in which electricity is generated feom chemical reaction.

Question 30

Heat of reaction

Answer 30

-heat given off or absorbed in a chemical reaction

Question 31

Exothermic reaction

Answer 31

-chemical reaction that gives off heat

Question 32

Endothermic reaction

Answer 32

-chemical reaction that absorbs heat

Question 33

Heat of combustion

Answer 33

-heat given off in a combustion reaction

Question 34

Percent yield

Answer 34

(Actual yield / Theoretical yield) x100

Question 35

Oxidation number/ oxidation state

Answer 35

The number of charges the atom would have in a molecule (or an ionic
compound) if electrons were transferred completely

Question 36

Ionic equation

Answer 36

Shows dissolved species as free ions

Question 37

1. Redox reactions and 2. Acid-base reactions

Answer 37

1. Transfer of electrons
2. Transfer of protons