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General Chemistry Practice Test 2 Key Concepts

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Terms in this set (37)

  • How to calculate molarity?
    Molarity is calculated as moles of solute divided by liters of solution. Use \(M = \frac{moles}{L}\).
  • What is the formula to find mass needed for a solution of known molarity?
    Mass = moles × molar mass. Moles = molarity × volume (in liters).
  • How to use dilution equation to find volume of stock solution?
    Use \(M_1 V_1 = M_2 V_2\), where M and V are molarity and volume before and after dilution.
  • How to calculate moles of ion in solution?
    Moles of ion = molarity × volume × number of ions per formula unit.
  • Which compounds are generally soluble?
    Most ammonium, alkali metal salts, and nitrates are soluble. Exceptions include some lead, barium, and silver salts.
  • What indicates a precipitation reaction?
    Mixing two aqueous solutions that form an insoluble solid (precipitate).
  • Define an Arrhenius acid.
    An Arrhenius acid produces H+ ions in aqueous solution.
  • List common strong acids.
    Strong acids include HCl, HNO3, HClO4, HI, and H2SO4.
  • How to write a complete ionic equation?
    Separate all strong electrolytes into ions, showing their physical states, and include precipitates as solids.
  • What are spectator ions?
    Ions that do not participate in the formation of a precipitate and remain unchanged in solution.
  • What is the net ionic equation for acid-base neutralization?
    The net ionic equation is \(\mathrm{H}^+ (aq) + \mathrm{OH}^- (aq) \rightarrow \mathrm{H_2O} (l)\).
  • How to assign oxidation state to phosphorus in K3PO4?
    Phosphorus has an oxidation state of +5 in K3PO4.
  • What is the oxidizing agent in Zn + Fe2+ → Zn2+ + Fe?
    Fe2+ is the oxidizing agent because it gains electrons (is reduced).
  • Which element is reduced in N2H4 + P + H2O → PH3 + NH2OH?
    Phosphorus (P) is reduced.
  • How to calculate concentration from titration data?
    Use molarity and volume of titrant and volume of analyte with stoichiometry to find unknown concentration.
  • How to convert pressure units from psi to mmHg?
    Use conversion factors: 1 atm = 14.7 psi and 1 atm = 760 mmHg.
  • How to find new pressure when volume changes (Boyle's Law)?
    Use \(P_1 V_1 = P_2 V_2\) assuming constant temperature.
  • Under what conditions do real gases behave ideally?
    At low pressure and high temperature, gases behave most like ideal gases.
  • What is Avogadro's Law?
    Volume of a gas is directly proportional to the number of moles at constant temperature and pressure.
  • How to use combined gas law?
    Use \(\frac{P_1 V_1}{T_1} = \frac{P_2 V_2}{T_2}\) to relate pressure, volume, and temperature changes.
  • How to calculate gas volume using ideal gas law?
    Use \(PV = nRT\), where R = 0.0821 L·atm/mol·K.
  • How to find molar mass from gas data?
    Molar mass = mass / moles; moles found from ideal gas law.
  • How to calculate gas density?
    Density = (Pressure × Molar Mass) / (R × Temperature).
  • What volume does 1 mole of gas occupy at STP?
    1 mole of gas occupies 22.4 L at STP.
  • Which gas has greatest density at STP?
    Gas with highest molar mass has greatest density at STP.
  • What affects rate of effusion?
    Lighter gases effuse faster; rate inversely proportional to square root of molar mass.
  • Define mean free path.
    Average distance a molecule travels between collisions.
  • How to convert Calories to Joules?
    1 Calorie = 1000 calories; 1 calorie = 4.18 Joules.
  • How to calculate change in internal energy (ΔE)?
    ΔE = heat (q) + work (w) done on the system.
  • What does a negative ΔE of the system mean?
    System loses energy; surroundings gain the same amount.
  • How to calculate heat of reaction from enthalpy and mass?
    Use stoichiometry and molar mass to find moles, then multiply by ΔHrxn per mole.
  • How to calculate heat required to raise temperature?
    Use \(q = m C_s \Delta T\), where Cs is specific heat capacity.
  • Characteristics of an endothermic reaction?
    Positive ΔH, absorbs heat, feels cold to the touch.
  • Which processes are endothermic?
    Sweat evaporating is endothermic; it absorbs heat.
  • How to calculate reaction enthalpy from standard enthalpies of formation?
    ΔH°rxn = Σ nΔHf(products) – Σ nΔHf(reactants).
  • How to find ΔH°rxn using Hess's Law?
    Combine given reactions and their ΔH values to find ΔH°rxn for target reaction.
  • How to calculate heat of solution per gram?
    Calculate q from temperature change, then divide by mass of solute.