Flashcards
Analytical Chem Test 2
Flashcards do conjunto (28)
- 1A Strong ElectrolyteA strong electrolyte totally ionized when dissolved in water. HCl is an example of a strong electrolyte
- 2A Bronsted-Lowry basea base is a molecule that accepts a protonwhen it encounters an acid base (proton donor). By this definition, NH3 can be a bronsted base
- 3A conjugate acid of a bronsted-lowery baseThe conjugate acid of a bronsted-lowry base is the potential proton donor formed when a bronsted-lowty base accepts a proton. For example, the NH4+is a conjugate acid in the reaction, NH3 + proton -> NH4+
- 4Neutralization in terms on bronsted lowry conceptNeutralization, according to the BL concept, occurs when a reaction involving an acid and its conjugate base in combined with a second reaction involving a base and its conjugate acid. NH3 + H2O -> NH4+ + OH-
- 5An amphiprotic solutean amphriprotic solute can act either as an acid or a base depending on the situation an amino acid in an amphiprotic solute.
- 6A zwitteriona switterion is a chemical species that bears both positive and negative charges. Free amino acids such as glycine, can exist as zwitterionin solution.
- 7Autoprotolysisautoprotolysis is the act of self-ionization to produce botha. conjugate acid and a conjugate base
- 8A weak acida weak acid only partially dissociates such that there are undissociated molecules and ions in aqueous solution. Acetic acid HOAc is an example of a weak acid
- 9La Chatlier's principlethe lachatelier principle states that the position of a n equlibrium always shifts in such a direction that it relieves the stress. A common ion like sulfate added to a solution containing sparingly soluble BaSO4 is an example
- 10the common ion effectthe common ion effect is responsible for the reduced solubility of an ionic precipitate when one of the soluble components reacting to form the precipitate. Chloride ion added to an AgCl solution decreases the solubility of Ag+ because of the common ion effect.
- 11an amphiprotic solventan emphiprotic solvent can act either as an acid or a base depending on the solute. Water is an example of an amphiprotic solvent since it can act as a proton donor or proton acceptor
- 12A differentiating solventa differentitating solvent reveals different strenghts of acid. By this definition, anhydrous acetic acid is a differentiating solvent because perchloric acid dissociated 5000 times more than hydrochloric acid.
- 13A leveling solventa leveling solvent shows no difference between strong acids. Perchloric acid and hydrochloric acid ionize completly in water; thus, water is a leveling solvent.
- 14a mass-action effect.A mass-action effect arises when a shift in a chemical equilibrium occurs due to the introduction o fone of the participating chemical species (i.e. additon of one of the reactants or products)
- 15Briefly explain why there is no term in an equlibrium-constant expression for water or for a pure solid, even though one (or both) appears in a balanced net ionic equation for the equlibrium.For dilute aqueous solutions, the concentration of water remains constant and is assumed to be independent of the equilibrium. This its concentration is included within the equlibrium constant. For a pure solid, the concentration of a chemical species in a solid phase is constant. As long as some solid exsists as a second phase, its effect on the equlibrium is constant and is included within the equilibrium constant.
- 16Difference between activity and activity coefficientactivity aA is the effective concentration of a chemical species A in solution. The activity coefficient is the numerical facror necessary to convery the molar concentraiton of the chemical specifes. A to activity as shown aA = yA[A]
- 17thermodynamic and cencentration equilibrium constants.The thermodynamic equilibirum constant refers to an ideal system within which each chmical species is unaffected by any others. A concentration equilibrium constant takes into account the influence exerted by solute species upon one another. The thermodynamic equlibrium is numerically constant and independent of ionic strength. The concentration equilibrium constant depends on molar concentration of reactants and products as well as other chemical species that may not participate in the equlibrium.
- 18List several general properties of activity coefficients1. activity coefficient depends on the solution ionic strengths
2. in very dilute solutions, the activity coefficient becomes smaller as the charge of the chemical species increases.
3. For a given ionic strength, the activity coefficient becomes smaller as the charge of the chemical species increases.
4. At any ionic strength, the activity coefficients are approximately equal for a chemical species having the same charge state. - 19neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged when NaOH is added to a dilute solution of: Mh(OH)2 (s)MgCl2 + 2NaOH -> Mg(OH)2 (s) + 2 NaCl
replacing divalent Mg^2+ with Na+ causes the ionic strength to decrease - 20neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged when NaOH is added to a dilute solution of: hydrochloric acidHCl + NaOH -> H2O + NaCl
there is no change in the charge states of the ions presen in the solution equilibria, The ionic strength is unchanged. - 21neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged when NaOH is added to a dilute solution of: acetic acidHOAc + NaOH -> H2) + NaOAc
the ionic strength will increase becuase NaOH and NaOAc are totally ionized wheras acetic acid is only partially ionized. - 22neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged with the addition of iron (III) chloride to: HClThe ionic strength will incraese when FeCl3 is added to HCl
- 23neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged with the addition of iron (III) chloride to: NaOH3NaOH + FeCl3 -> Fe(OH)3 (s) + 3 NaCl
the addition of FeCl3 to Na OH replaces a univalent OH- with univalent Cl- thus, the ionic strength is unchanged - 24neglecting: volume changes, would you expec the ionic strength to increase decrease or remain unchanged with the addition of iron (III) chloride to: AgNO33AgNO3 + FeCl3 -> Fe(NO3)3 + 3AgCl (s)
Addition of FeCl3 replaces the univalent Ag+ with the trivalent Fe^3+; thus, the ionic strength increases - 25Explain why the activity coefficent for dissolved ions in water is usually less than that for water itself?Water is a neutral molecule and its activity equals the concentration at all low to moderate ionic strengths, activity coefficients of ions decrease with increasing ionic strength becuase ionic atmosphere surrounding the ion causes it to lose some of its chemical effectiveness and its activity is less than its concentration
- 26Explain why the activity coefficient for a neutral molecule is usually 1There is no ionic atmosphere surrounding a neutral molecule and so its activity does not change with increaseing ionic strength. Hence its activity coefficient is essentially unity and its activity is equal to its concentration.
- 27Explain why the initial slope for Ca2+ in fugure 8-3 is steeper than that for K?Multiply charged ions deviate from ideality more than singly charged ions becuase of hte effect of the surrounding ionic atmosphere. The initial slope of the activity coefficient vs square root of ionic strength for Ca2+ is steeper than that for K because the activity coefficient of Ca2+ is more influenced by ionic strength then that for K.
- 28What is the numerical value of the activity coefficient of aqueous ammonia (NH3) at an ionic strength of 0.2Ammonia (NH3) is an uncharged molecule and this its activity coefficient is unity.
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- Criado por Julia K · 18 fev 2024
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