Aqueous Reactions and Solution Stoichiometry

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Aqueous Reactions and Solution Stoichiometry

• Chapter 4 BLB 11th

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4.1 General Properties of Aqueous Solutions

• Solution homogeneous mixture (ch. 13)
• Solvent dissolving medium aq-water
• Solute dissolved substance
• Electrolytic Properties
• Electrolyte a substance whose aqueous solution
  contains ions conducts electricity

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Aqueous Solutions, cont.

• Ionic Compounds in Water
• Ionic solids dissociate (or ionize) into ions as
  they dissolve.
• hydration process of dissolving an ionic
  substance in water
• solvation dissolving in any solvent
  dissolution
• Why? Water is polar.

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Polarity of molecules

• Electrons are shared unequally.
• Results in partial charges (d), and a
• Dipole moment

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Hydration of NaCl(s)
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Aqueous Solutions, cont.

• Molecular Compounds in Water
• nonelectrolytes contain only molecules (no
  ions) do not dissociate do not conduct
  electricity may dissolve in water
• Most molecular compounds are nonelectrolytes.
• Some may have strong interaction with water
  (alcohols).
• Some may dissociate (acids).

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Methanol (CH3OH) in water
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Aqueous Solutions, cont.

• Strong and weak electrolytes
• Depends on the extent of ionization
• Strong completely dissociate
• - most ionic compounds, strong acids bases
• Weak produce very few ions establish chemical
  equilibrium
• - weak acids (like acetic acid) and weak bases
  (like amines) water
• Note strong doesnt mean soluble and vv.

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4.2 Precipitation Reactions

• Marked by the formation of an insoluble product
  (precipitate)
• Solubility amount of solute that can be
  dissolved in a given amount of solvent at a
  certain temperature g/100g or g/L or mol/L
• Insoluble solubility lt 0.01 mol/L
• Solubility Rules Table 4.1, p. 125
• Metathesis (or exchange) reactions

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Note All common compounds of Group I metals and
NH4 are soluble in water.
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Metathesis (or exchange) reactions

• Molecular
• BaCl2(aq) Na2SO4(aq) ? 2 NaCl(aq) BaSO4(s)
• Complete ionic
• Net ionic

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Metathesis (or exchange) reactions

• Molecular
• NaI(aq) Pb(NO3)2(aq) ?
• Complete ionic
• Net ionic

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Metathesis (or exchange) reactions

• Molecular
• NaOH(aq) Co(NO3)2(aq) ?
• Complete ionic
• Net ionic

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4.3 Acid-Base Reactions

• Involve H
• Acid H donor
• Base H acceptor
• Neutralization
• acid base ? salt water
• HCl NaOH ? NaCl H2O

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4.4 Oxidation-Reduction (Redox) Reactions

• Involve transfer of e
• Oxidation loss of e
• Reduction gain of e
• Oxidation state or number a charge assigned
  to an atom to keep track of electrons transferred
  during redox
• Displacement reaction ion in solution is
  replaced through oxidation of an element.

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Oxidation of Mg Mg(s) 2 H(aq) ? Mg2(aq)
H2(g)
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4.5 Concentrations of Solutions

• Molarity (M) mole solute/L solution
• Dilution adding solvent to decrease
  concentration
• M1V1 M2V2
• mol1 mol2 only volume changes

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Calculate the concentration (in M) if 2.50 g
(NH4)2SO4 is dissolved in enough water to form
250 mL of solution.
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How many grams of K2Cr2O7 are needed to make 50.0
mL of 0.850 M solution?
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What volume (in mL) of 6.0 M HNO3 is needed to
make 250 mL of 1.0 M HNO3?
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4.6 Solution Stoichiometry and Chemical Analysis

• Use M and volume to obtain moles
• Titration process used to determine the
  concentration of a solution (p. 150ff)
• Standard solution one of precisely known
  concentration
• Analyte solution of unknown concentration