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Gen Chem > Ch. 4: Compounds and Stoichiometry > Flashcards

Ch. 4: Compounds and Stoichiometry Flashcards

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1
Q

what are the two laws of conservation that must be followed when balancing chemical equations?

A
  1. law of conservation of mass
  2. law of conservation of charge

the number of atoms of each element on the reactant side equals the number of atoms of that element on the product side

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2
Q

what do stoichiometric coefficients indicate?

A

these are the numbers placed in front of each compound

used to indicate the relative number of moles of a given species involved in the reaction

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3
Q

what are the steps to balancing a chemical reaction?

A

see p. 138

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4
Q

defn: molecule

A

a combination of two or more atoms held together by covalent bonds

ionic compounds do not form true molecules because of the way in which the oppositely charged ions arrange themselves in the solid state = technically a formula unit with a formula weight

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5
Q

defn + unit: molecular weight

A

the sum of the atomic weights of all the atoms in a molecule
units are atomic mass units (amu) per molecule

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6
Q

defn + unit: formula weight

A

of an ionic compound

the sum of the atomic weights of the constituent ions according to its empirical formula

units: amu per molecule

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7
Q

defn: mole

A

a quantity of any substance equal to the number of particles that are found in 12 grams of carbon-12 (Avogadro’s number)

one mole of a compound has a mass in grams equal to the molecular or formula weight of the compound in amu

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8
Q

defn: Avogadro’s number

A

6.022 x 10^23 mol^-1

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9
Q

defn + unit: molar mass

A

the mass of one mole of a compound

unit: g/mol

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10
Q

defn: equivalents

A

how many moles of the thing we are interested in (protons, hydroxide ions, electrons, or ions) will one mole of a given compound produce?

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11
Q

defn + eqn: gram equivalent weight

A

the amount of a compound (in grams) that produces one equivalent of the particle of interest

gram equivalent weight = molar mass/n

where n is the number of particles of interest produced or consumed per molecule of the compound in the reaction

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12
Q

eqn: if the amount of a compound is known and we need to determine how many equivalents are present:

A

equivalents = mass of compound (g)/gram equivalent weight (g)

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13
Q

defn: normality (N)

A

a measure of concentration given in the units equivalents/L

always assume that a reaction will proceed to completion

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14
Q

eqn: conversion from normality to molarity of a given solute

A

Molarity = Normality/n

where n is the number of protons, hydroxide ions, electrons, or ions produced or consume by the solute

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15
Q

defn: structural formulas

A

skeletal representations of compounds that show the various bonds between the constituent atoms of a compound

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16
Q

defn: 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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17
Q

defn: empirical formula vs. molecular formula

A

EMPIRICAL = gives the simplest whole-number ratio of the elements in the compound

MOLECULAR = gives the exact number of atoms of each element in the compound (is a multiple of the empirical formula)

18
Q

defn + eqn: percent composition

A

percent composition of an element (by mass) = the percent of a specific compound that is made up of a given element

percent composition = mass of element in formula/molar mass x 100%

can use empirical or molecular formula

19
Q

defn: combination reaction

A

has two or more reactants forming one product

A + B –> C

20
Q

defn: decomposition reaction

A

the opposite of a combination reaction

a single reactant breaks down into two or more products, usually as a result of heating, high-frequency radiation, or electrolysis

A –> B + C

21
Q

what does the delta sign over a reaction arrow represent?

A

the addition of heat

22
Q

defn: combustion reaction

A

a special type of reaction that involves fuel (usually a hydrocarbon) and an oxidant (normally oxygen)

in the most common form: these reactants form the two products of carbon dioxide and water

23
Q

defn: single-displacement reaction

A

an atom or ion in a compound is replaced by an atom or ion of another element

ex: Cu (s) + AgNO3 (aq) –> Ag (s) + CuNO3 (aq)

24
Q

defn: double-displacement reactions (metathesis reactions)

A

elements from two different compounds swap places with each other to form two new compounds

occurs when one of the products is removed from the solution as a precipitate or gas when two of the original combine to form a weak electrolyte that remains undissociated in solution

ex: CaCl2 (aq) + 2 AgNO3 (aq) –> Ca(NO3)2 (aq) + 2 AgCl (s)

25
Q

defn: neutralization reactions

A

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

ex: HCl (aq) + NaOH (aq) –> NaCl (aq) + H2O (l)

26
Q

when balancing equations, should you focus on the least represented elements first or the most represented elements first?

A

LEAST then work your way to the most

27
Q

defn: limiting reagent/reactant

A

the reactant that is used up or consumed first in a reaction

it limits the amount of product that can be formed in the reaction

28
Q

defn: excess reagents (reactants)

A

the reactants that remain after all the limiting reagent is used up

29
Q

what are the 2 principles to keep in mind when determining the limiting reagent?

A
  1. all comparisons of reactants must be done in units of moles (gram-to-gram comparisons will be useless or misleading)
  2. it is not the absolute mole quantities of the reactants that determine which reactant is the limiting reagent –> instead the rate at which the reactants are consumed (the stoichiometric ratios of the reactants), combined with the absolute mole quantities determines which reactant is the limiting reagent
30
Q

defn: theoretical yield vs. actual yield

A

THEORETICAL = the maximum amount of product that can be generated as predicted from the balanced equation, assuming that all of the limiting reactant is consumed, no side reactions have occurred, and the entire product has been collected

ACTUAL = the amount of product one actually obtains during the reaction

31
Q

defn + eqn: percent yield

A

the ratio of the actual yield to the theoretical yield, multiplied by 100

percent yield = actual yield/theoretical yield x 100%

32
Q

defn: ferrous vs. ferric
cuprous vs. cupric

A

FERROUS = Fe2+
FERRIC = Fe3+

CUPROUS = Cu+
CUPRIC = Cu2+

33
Q

how are monatomic anions named?

A

by dropping the ending of the name of the element and adding -ide
H- = hydride
F- = fluoride
O2- = oxide
S2-= sulfide
N3- = nitride
P3- = phosphide

34
Q

how are polyatomic anions that contain oxygen (oxyanions) named?

A

when an element forms two oxyanions, the name of the one with less oxygen ends in -ite, and the one with more oxygen ends in -ate

NO2- = nitrite
NO3- = nitrate

SO32- = sulfite
SO42- = sulfate

35
Q

mnemonic: oxyanions

A

the lITEst anions have the fewest oxygens

the heaviest anions ATE the most oxygens

36
Q

defn: hypo- and per- (ionic compound nomenclature)

A

hypo- = less oxygen
per- = more oxygen

ClO- = hypochlorite
ClO2- = chlorite
ClO3- = chlorate
ClO4- = perchlorate

37
Q

how are polyatomic anions that gain one or more H+ ions to form anions of lower charge named?

A

by adding the word hydrogen or dihydrogen to the front of the anion’s name

HCO3- = hydrogen carbonate OR bicarbonate
HSO4- = hydrogen sulfate OR bisulfate
H2PO4- = dihydrogen phosphate

38
Q

why are ionic compounds good conductors of electricity in aqueous solutions?

A

the lattice arrangement is disrupted by the ion-dipole interactions between the ionic components and the water molecules

the cations and anions are now free to move and the solution of ions is able to conduct electricity

39
Q

defn: electrolytes

A

solutes that enable solutions to carry currents

the electrical conductivity of aqueous solutions is governed by the presence and concentration of ions in the solution

40
Q

defn: strong electrolyte vs. weak electrolyte vs. nonelectrolyte

A

a solute is considered a strong electrolyte if it dissociates completely into its constituent ions

weak electrolyte: ionizes or hydrolyzes incompletely in aqueous solution and only some of the solute is dissolved into its ionic constituents

nonelectrolyte = compounds that do not ionize at all in water, retaining their molecular structure in solution

Gen Chem (12 decks)

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