Atoms, Molecules, Ions, and water

Question 1

Notations for Atoms

Answer 1

X = element Symbol
A = Atomic mass number = # of proton + # of neutrons
Z= Atomic # = # of protons = # of electrons in a neutral atom.

Question 2

Dalton’s Atomic Theory

Answer 2

1. Each element made up atoms
2. Atoms in an elements are identical
3. Chemical compounds form when atoms of different element combine with each other
4. Chemical reaction = reorganization of atoms

Question 3

Isotopes

Answer 3

Atoms with same atomic number (z) but different mass number (A)
has a different # of Neutrons

Question 4

Element

Answer 4

Pure substance with only one type of atoms
eg. Ag, Mg, Fe
Eg2. H2, N2, O2

Question 5

Compound

Answer 5

Pure substance with two or more different atoms

Question 6

Molecules

Answer 6

Combination of atoms
Represented by chemical formulae
Eg. CO2, H2O

Question 7

Anion

Answer 7

Negatively charged molecule/element (-)

Eg. Cl-

Question 8

Cation

Answer 8

Positively charged molecule/element(+)

Eg. Na+

Question 9

Atomic mass spectrometry

Answer 9

separates ions by mass-to-charge ratio

Question 10

Atomic mass

Answer 10

Based all on Carbon 12

Question 11

Mol

Answer 11

1 mol = 6.022 x 10e23

Question 12

Molar Mass

Answer 12

Mass in g of 1 mole of that substance

Question 13

Mass percent

Answer 13

the mass of an element in a compound expressed as a % of the total mass of the compound

Question 14

Molecular Formula

Answer 14

exact # of atoms in one molecule of the compound

Eg. C2H6Br2

Question 15

Empirical formula

Answer 15

the formula that expresses the smallest whole number ratio of atoms in a compound
Eg. CH3Br

Question 16

Empirical formula calculation

Answer 16

1. burn sample in the presence of O2: convert C to CO2 and H to H2O:
2. determine the % of carbon and hydrogen
   from the masses of CO2 and H2O
3. calculate # of moles from the elemental masses based on a 100g sample
4. divide each mole by the smallest #.

Question 17

Limiting reactant

Answer 17

The limiting reactant or limiting reagent is a reactant in a chemical reaction that determines the amount of product that is formed.

Question 18

Percent yield

Answer 18

change conditions of the reaction and monitor an increase or decrease in the % yield

Question 19

Theoretical yield

Answer 19

“predicted” amount of product Theoretical yield is dictated by limiting reagent

Question 20

Actual yield

Answer 20

Reality: obtained less than Theoretical yield

Question 21

Percent yield

Answer 21

Actual yield(g) / theoretical yield (g) x 100%

Question 22

Solving stoichiometric questions

Answer 22

1. Balance equations
2. Convert known mass to mol
3. Determine limiting reagent
4. Use limiting reagent to determine mol of desired product
5. Convert mol to grams

Question 23

Water

Answer 23

Polar covalent bond
Difference in electronegativity between O and H
Bonding electron pairs are shared unevenly

Question 24

Water

Answer 24

O atoms has 2 lone pairs: difference b/w lone pairs and H atoms result in a bent structure.

Question 25

Electronegativity

Answer 25

Atom’s tendency to attract electrons
Increase as you go across
Decrease as you go down

Question 26

Polar Solvents

Answer 26

Dissolves ionic solids by forming a shell around the ion

Process of solvation

Question 27

Hydration

Answer 27

Ionic solids forming a shell around the ion

Solvation of water.

Question 28

3 groups of polar substances based on electroconductivity

Answer 28

1. Strong electrolytes: Compounds that are completely ionized in a solution. Eg. Soluable salts & strong Acid/base
2. Weak Electroyltes: Compounds that only partially ionizes in solution
3. Non-electrolytest: Substance that are solvable but do not ionize. Eg. sugar, alcohol.

Question 29

Molarity

Answer 29

Mol/L