Chem 1c – Chemistry Test Questions

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factors that influence reaction rate
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concentration, physical state, temperature
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reaction rate in terms of products
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rate= -Δ[A]/Δt
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rate law
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rate=k[A]^m[b]^n

*m and n are the stoichimetric coefficients if the reaction is elementary… otherwise you have to find them experimentally

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reaction orders
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how the rate is affected by reactant concentration.
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rate constants
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are specific for a particular reaction AT A PARTICULAR TEMPERATURE!!!
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units for rate constant k for an overall zeroth order reaction
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mol/L s
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units for a rate constant k for an overall 1st order reaction
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1/s
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units for rate constatnt k for an overall second order reaction
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L/mol s
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use of integrated rate laws
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used to solve for concentrations, times, or rate constants when you want to consider time a factor
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integrated rate law in straight line form for zeroeth order reaction
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[A]=-kt + [A]0
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Integrated rate law in straight line form for a 1st order reaction
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ln [A]=-kt + ln[A]0
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Integrated rate law in straight line form for a 2nd order reaction
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1/[A]=kt+1/[A]0
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half life for a zeroeth order reaction
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[A]0/2k
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half life for a 1st order reaction
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(ln2)/k
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half life for a 2nd order reaction
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1/k[A]0
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Arrhenius equation
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k=Ae^(-Ea/RT)

A=frequency factor

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What happens as T increases, according to the Arrhenius equation?
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k increases, and therefore the rate increases.
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If the Ea forward is larger than the Ea reverse, is the process endothermic or exothermic?
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endothermic
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If the Ea reverse is larger than the Ea forward, is the reaction endothermic or exothermic?
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exothermic
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According to the Arrhenius equation, as Ea increases, what happens to k and rate?
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k decreases, which leads to a decreased rate.
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what is a spontaneous reaction?
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one proceeding towards equilibrium.
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what is the sign of ΔS for the following rxns:
solid–>liquid–> gas
crystalline solid + liquid-> ions
crystaline solids-> gases + ions
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ΔS>0
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microstate (W)
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each quantized state of a system (energy levels)
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equations for ΔS of a system
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ΔS (sys)=q/T

** RECAll q= cmΔT!!!!!!

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Entropy in similar compounds
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for similar compounds, entropy increases with molar mass
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determining spontaneity using entropy
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ΔS (universe)>0 means spontaneous

** note… must take into consideration ENTIRE univers, so ΔS sys+ ΔS surr

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entropy in relationship to equilibrium
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ΔS (univ)=0 therefore

ΔS (sys)=-ΔS (surr)

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phase changes in relationship to equilibrium
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phase changes occur at equilibrium
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exothermic reactions
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ΔH0
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endothermic reactions
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ΔH>0, so ΔS(surr)<0
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free energy equation
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ΔG=ΔH-TΔS

**WOrd of Caution– if rxn is not at 298 k, then you MUST use this formula, because the tables are made at 298 K!!!!

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spontaneity in relation with gibbs free energy
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ΔG<0 spontaneous
ΔG>0 nonspontaneous
ΔG=0 equilibrium
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4.18 joules is…
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the heat required to heat one gram of water by 1 C.
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does vapor pressure for a liquid increase as the temperature increases?
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why yes, it does.
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do fast reactions have large equilibrium constants?
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not necessarily. Keq=K1/K(-1), and the reaction could occur quickly in both directions.
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are activation energies for forward and reverse reactions the same?
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nope. draw some pictures.
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will the equilibrium constant for a reaction increase if a catalyst is added?
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nope, catalysts only affect the activation energy.
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are the rates of forward and reverse reactions equal at equilibrium?
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yes, this is the definition of equilibrium
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equilibrium
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when the reaction rates for the forward and reverse processes are equal
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H2O2
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hydrogen peroxide
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definition of enthalpy
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ΔH=ΔE+PΔV
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1st law of thermodynamics
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ΔE=q+w
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ethanol
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C2H5OH
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octane
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C8H18
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combustion
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adding oxygen gas to form carbon dioxide and water
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molality
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mol/kg
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ΔH(soln) without ions
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ΔH(soln)=ΔH(solute) + ΔH(solvent) + ΔH(mix)
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ΔH(soln) with ions
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ΔH(soln)=ΔH(lattice)+ΔH(hydration)
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Osmotic pressure
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pi=MRT

M=molarity
R=gas constant
pi=osmotic pressure

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charge density: periodic trends
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charge density increases as you move across the periodic table, and decreases as you move down

inc
——–>
|
|
| dec
/

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miscible
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solute and solvent are soluble in each other in any proportion.
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list these major types of intermolecular forces in order of decreasing strength:

  • dipole-dipole,
  • H bond,
  • ion-induced dipole,
  • dipole induced dipole,
  • ion-dipole,
  • dispersion
  • answer

  • ion-dipole,
  • H bond,
  • Dipole-dipole,
  • ion-induced dipole,
  • dipole-induced diole,
  • dispersion.
  • question

    what kind of intermolecular forces are seen with the use of soap to remove grease?
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    dipole-induced dipole
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    hydroxyl
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    -OH group
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    methanol
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    CH3OH
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    ethanol
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    CH3CH2OH
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    how is charge density related to heat of hydration?
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    the higher the charge density,the more negative ΔH (hydration) is
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    entropy
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    a thermodynamic variable directly related to the number of ways that a system can distribute its energy.
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    gas solubility and rising temperature
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    gas solubility in water decreases with rising temperature

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