4: Compounds and Stoichiometry Flashcards Preview

MCAT Chem > 4: Compounds and Stoichiometry > Flashcards

Flashcards in 4: Compounds and Stoichiometry Deck (24):
1

compounds

pure substances composed of 2+ elements in a fixed proportion

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molecules

combination of 2+ atoms held together by covalent bonds ex. CO2

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formula unit

empirical formula of an ionic compound (instead of molecule)

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Normality (N)

measure of concentration (equivalents/L)

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Molarity

Normality/n

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gram equivalent weight in acid base chemistry

mass of acid that yields one mole of protons or mass of base that yields one mole of hydroxide ions

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law of constant composition

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

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empirical formula

simplest whole-number ratio of the elements in a compound

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molecular formula

exact number of atoms of each element in the compound... multiple of empirical

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percent composition

percent of a specific compound that is made up of a given element

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combination reaction

2+ reactants forming a product: A + B --> C

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decomposition reaction

single reactant breaks down into 2+ products: A --> B + C

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combustion reactions

usually conducted with hydrocarbon fuels and involves oxidation

hydrocarbon + oxygen --> CO2 +H2O

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single-displacement reaction

atom/ion in a compound is replaced by an atom/ion of another element... aka oxidation-reduction rxns

ex. Cu (s) + AgNO3 (aq) --> Ag (s) + CuNO3 (aq)

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double-displacement reactions/metathesis reactions

elements from 2 different compounds swap places with each other to form 2 new compounds

  • occurs when one of the products is removed from the solution as a precipitate or gas or when 2 of the original species combine to form a weak electrolye that remains undissociated in solution

CaCl2 (aq) + 2AgNO3 (aq) --> Ca(NO3)2 (aq) + 2AgCl (s)

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neutralization reactions

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

ex. HCl (aq) + NaOH (aq) --> NaCl (aq) + H2O (l)

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mole of gas at STP conversion

22.4 L

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monoatomic anion naming

drop ending of name and add -ide

ex. H- hydride, F- Flouride, S2-  Sulfide

 

 

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polyatomic anions/oxyanions

hypo-, -ite, -ate, per-

ex. ClO- hypochlorite, ClO2- chlorite

ClO3- chlorate,ClO4perchlorate

ex. NO2Nitrite, NO3- Nitrate

ex. SO32- sulfite, SO42- sulfate

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polyatomic anions with H+ ions

add hydrogen or dihydrogen

ex. HCO3hydrogen carbonate/bicarbonate

HSO4hydrogen sulfate/bisulfate

H2PO4dihydrogen phosphate

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common polyatomic ions

NH4Ammonium

C2H3O2- Acetate

CN- Cyanide

MnO4- Permanganate

SCNthiocyanate

CrO42- chromate

Cr2O72- dichromate

BO33borate

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metals that form more than one positive ion

  • charge indicated by Roman numeral in parenthesis
  • -ous for lesser charge
  • -ic for greater charge

ex. Cu+ Copper(I) or Cuprous, Cu2+ Copper (II) or Cupric

ex. Fe2+ Iron(II) or Ferrous, Fe3+ Iron(III) or Ferric

 

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electrolytes

solutes that enable solutions to carry currents

  • ionic compounds make good electrolytes because they dissolve most readily 
  • electrical conductivity of aqueous solutions is governed by the presence and concentration of ions in the solution

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tendency of ionic solvent to solvate

  • strong electrolyte if it dissociates completely into its constiuent ions
    • ex. NaCl, KI, HCl in water
  • weak electrolyte if ionizes or hydrolyzes incompletely in aqueous solution and only some of solute is dissolved into its ionic constituents
    • ex. acetic acids, weak acids, ammonia, weak bases
  • nonelectrolyte of compound does not ionize at all in water
    • ex. nonpolar gases, organic compounds