Chem 1c – Chemistry Test Questions – Flashcards
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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: |
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| 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 |
