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MCAT Chem > Chem #4 > Flashcards

Chem #4 Flashcards

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1
Q

compound

A

pure substance composed of two or more elements in a fixed proportion

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2
Q

formula unit

A

the empirical formula of a compound (such as NaCl in which an actual molecule does not exist because it is just a big lattice structure).

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3
Q

formula weight

A

weight of the formula unit, adding up the atomic weights of the constituent ions according to its empirical formula.

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4
Q

molecular weight

A

the sum of the atomic weights of all the atoms in a molecule, and its units are atomic mass units (amu) per molecule.
o Atomic weight: weighted average of the masses of the naturally occurring isotopes of an element, not their weights.

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5
Q

mole

A

: a quantity of any substance (atoms, molecules, dollar bills, kittens) equal to the number of particles found in carbon-12.
o Number of particles is Avogadro’s number: 6.022 x 1023 mol-1
o Ex: one molecule of a compound has a mass of 62 amu and one mole of the compound has a mass of 62 grams.

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6
Q

molar mass

A

the mass of one mole of a compound (g/mol).

o Molecular weight is in amu/molecule

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7
Q

equivalent weights

A

how many moles of the thing we are interested in will one mole of a given compound produce
o Ex: HCl can donate one mole of H+ per mole of HCl
o Ex: Na can donate one mole of e- per mole of Na
o What it donates is known as the equivalent.

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8
Q

gram equivalent weight

A

the amount of a compound, measured in grams, that produces one equivalent of the particle of interest: = molar mass/n
 n: the number of particles of interest produced or consumed per molecule of the compound in the reaction.
 The mass that provides one mole of the particle of interest.
 Equivalents = mass of compound / gram equivalent weight

Units are in grams/thing of importance (Ex: moles of H+)

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9
Q

normality

A

measure of concentration, given in the units of equivalents/L
 Molarity = Normality / n
• n: the number of protons, hydroxide ions, electrons, or ions produced or consumed by the solute.
• Ex: monoprotic or diprotic acid

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10
Q

law of constant composition

A

any pure sample of a given compound will contain the same elements in an identical mass ratio

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11
Q

empirical formula

A

the simplest whole-number ratio of the elements in the compound
o CH2O is indicative of the empirical formula of a monosaccharide.

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12
Q

molecular formula

A

: the exact number of atoms of each element in the compound and is a multiple of the empirical formula.

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13
Q

percent composition

A

of an element by mass, the percent of a specific compound that is made up of a given element (all of this given element, could be three atoms of it).
o Percent composition = (mass of element in formula / molar mass) x 100

SPECIFIC COMPOUND

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14
Q

combination reaction

A

has two or more reactants forming one product.

o A + B  C

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15
Q

decomposition reaction

A

: a single reactant breaks down into two or more products (usually as a result of heating, high-frequency radiation, or electrolysis.
o A  B + C

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16
Q

combustion reaction

A

special type of combustion reaction that involves a fuel (usually a hydrocarbon) and an oxidant (normally oxygen). Involves oxidation of a fuel.
o CxHy + O2  CO2 + H2O
o Can use sulfur or other sugars as fuels.

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17
Q

Longer hydrocarbon chains yield ____

A

greater amounts of combustion products and release more heat in the process.

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18
Q

single-displacement reaction

A

an atom or ion in a compound is replaced by an atom or ion of another element.
o A + BC  B + AC
o Common oxidation-reduction reaction

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19
Q

double-displacement reaction

A

displacement (metathesis) reaction: elements from two different compound swap places with each other to form two new compounds.
o AB + CD  AD + BC
o Sometimes one of the products leaves as gas or does not dissociate (s)
o Neutralization Reactions: specific type of double displacement reaction in which an acid reacts with a base to produce a salt (and usually water)

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20
Q

metathesis = _____

A

another word for double displacement reaction

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21
Q

neutralization reaction

A

specific type of double displacement reaction in which an acid reacts with a base to produce a salt (and usually water)

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22
Q

law of conservation of mass

A

the mass of the reactants consumed must equal the mass of the products generated.

23
Q

law of conservation of charge

A

The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved.
o Charge is same on both sides of the equation.

24
Q

if stuck balancing a chemical reaction:

A

o IF STUCK, take a guess for the coefficient of the first element and then balance accordingly

25
Q

1 mole of any substance has how many particles:

A

= 6.022 x 1023 particles

26
Q

limiting reagant

A

the reactant that is used up first, limits the amount of product that can be formed in the reaction.

27
Q

theoretical yield

A

: the maximum about of product that can be generated as predicted from the balanced equation, assuming that all of the limiting reactant is consumed and no side reactions occur.

28
Q

percent yield

A

(actual/theoretical) x 100%

29
Q

actual yield

A

the amount of product one actually obtains during the reaction.

30
Q

actual yield

A

the amount of product one actually obtains during the reaction.

31
Q

oxidation states and color

A

 The color of a solution can be indicative of the oxidation state of a given element in the solution. Same element undergoes different electron transitions in different ox states and therefore absorbs different frequencies of light.

32
Q

ionicity

A

how ionic something is.

33
Q

Oxyanions of the halogens, the halogens have positive oxidation states

A

ClO-

Cl +1, O-2

34
Q

electrolytes

A

solutes that enable solutions to carry currents.

35
Q

what are the best electrolytes?

A

best are ionic compounds with high dissociation constant.

Best have most ions and most magnitude

36
Q

solvate

A

ionic solution dissolving. Solvation is degree of dissociation.

37
Q

strong electrolytes

A

dissolves completely into its constituent ions.

• Ex: NaCl, HCl, KI

38
Q

____ compounds do not form true molecules because of the way in which the oppositely charged ions arrange themselves in the solid state.

A

ionic

39
Q

what are the units of molecular weight? How is it different than molar mass?

A

amu/molecule

molar mass: grams/mole

40
Q

the periodic table shows weights of elements in what units?

A

amu

41
Q

One molecule of H2CO3 has a mass of ____ amu and one mole of the compound has a mass of ___ grams

A

62 amu

62 grams

42
Q

calculate equivalents

A

Equivalents = mass of compound / gram equivalent weight

43
Q

a 2 N solution of acid contains a concentration of hydrogen ions equal to _____ moles per liter. For a solution of H2CO3 with 2 N, the molarity of H2CO3 is ______

A

1

44
Q

____ only have empirical formulas and not molecular formulas

A

ionic compounds

45
Q

steps to find empirical formula given percentage by masses:

A
  • call the percentages grams
  • convert to moles
  • divide by smallest integer
  • balance if fraction
  • there it is
46
Q

one mole of any gas at STP = _____

A

22.4 L

47
Q

one mole of any gas at STP = _____

A

22.4 L

48
Q

identify the ion:

  • ferrous
  • ferric
  • cuprous
  • cupric
  • hydride
  • fluoride
  • oxide
  • sulfide
  • nitride
  • phosphide
A 
Fe+2
Fe+3
Cu+
Cu+2
H-
F-
O-2
S-2
N-3
P-3
49
Q 
Extended series of oxyanions, name the following: 
ClO-
ClO2-
ClO3-
ClO4-
A

hypochlorite
chlorite
chlorate
perchlorate

50
Q

_____ are not typically found in their uncharged state in nature because they are highly reactive

A

alkali metals

51
Q

in oxyanions of the halogens, the halogen is assigned a ______ oxidation state

A

positive

52
Q

why aren’t ionic compounds when they are in their solid form good conductors?

A

the charged particles of the ionic bonds are rigidly set in place and can’t move

53
Q

the best electrolytes have ______ cations and anions and the ____ charge

A

the most

highest

MCAT Chem (12 decks)

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