Compounds and Stoichiometry Flashcards

1
Q

compounds

A

substances composed of two or more elements in a fixed composition

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2
Q

molecular weight

A

mass (in amu) of the constituent atoms in a compound as indicated by the molecular formula

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3
Q

molar mass

A

mass of one mole of a compound; measured in grams per mol

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4
Q

Avogadro’s number

A

6.022 x 10^23

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5
Q

gram equivalent weight

A

a measure of the mass of a substance that can donate one equivalent of the species of interest
GEW = molar mass/n

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6
Q

normality

A

ratio of equivalents per liter; related to molarity by multiplying the molarity by the number of equivalents present per mole of compound

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7
Q

equivalents

A

moles of the species of interest; most often seen in acid-base chemistry (H+ ions or -OH ions) and redox reactions (moles of e-‘s or other ions)

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8
Q

law of constant composition

A

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

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9
Q

empirical formula

A

smallest whole-number ratio of the elements in a compound

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10
Q

molecular formula

A

either the same as or a multiple of the empirical formula; gives the exact number of atoms of each element in a compound

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11
Q

calculating percent composition by mass

A

determine mass of individual element and divide by the molar mass of the compound

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12
Q

combination reactions

A

occur when two or more reactants combine to form one product

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13
Q

decomposition reactions

A

occur when one reactant is chemically broken down into two or more products

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14
Q

combustion reactions

A

occur when a fuel and an oxidant (typically O) react, forming the products H2O and CO2 (if the fuel is a hydrocarbon)

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15
Q

displacement reactions

A

occur when one or more atoms or ions of one compound are replaced with one or more atoms or ions of another compound

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16
Q

single-displacement reactions

A

occur when an ion of one compound is replaced with another element

17
Q

double-displacement reactions

A

occur when elements from two different compounds trade places with each other to form two new compounds

18
Q

neutralization reactions

A

when an acid reacts with a base to form a salt (and, usually, H2O)

19
Q

determining balanced equations

A

in order to perform stoichiometric calculations

  1. balance least common atoms
  2. balance more common atoms (H and O)
  3. balance charge, if necessary
20
Q

limiting reagent

A

determined by balanced equations; reactant that will be consumed first in a chemical reaction

21
Q

excess reagents

A

other reactants present besides limiting reagent

22
Q

theoretical yield

A

amount of product generated if all of the limiting reactant is consumed with no side reactions

23
Q

actual yield

A

typically lower than the theoretical yield

24
Q

percent yield

A

calculated by dividing actual yield by theoretical yield and converting to percentage
% yield = (actual yield/theoretical yield) x 100

25
Roman numerals (ions)
used for non representative elements to denote charge
26
-ous ending (ions)
indicate lesser charge
27
-ic ending (ions)
indicate greater charge
28
-ide (ions)
all monoatomic anions
29
oxyanions
``` given a suffix to indicate how oxidized central atom is -ite --> contain lesser amount of O -ate --> contain greater amount of O hypo- --> species with fewest O per- --> species with most O ```
30
hydrogen or bi- (ions)
denotes single H in polyatomic ions
31
dihydrogen (ions)
denotes two H's in polyatomic ions
32
ion charges
predictable by group # and type of element (metal or nonmetal) for representative elements but generally unpredictable for non representative elements - metals form positively charged cations based on group # - nonmetals form negatively charged anions based on # of e-'s needed to achieve octet
33
electrolytes
contain equivalents of ions from molecules that dissociate in solution
34
degree of solvation/dissociation
determines strength of electrolyte
35
Moles from mass
moles = mass of a sample/molar mass
36
equivalents from mass
equivalents = mass of compound/gram equivalent weight
37
molarity from normality
molarity = molar mass/n
38
percent composition
% composition = (mass of element in formula/molar mass) x 100