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General Chemistry Key Concepts and Calculations

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  • Which cation forms a precipitate with a compound that releases CO2 upon acid addition?
    Cr3+ forms a precipitate in this scenario.
  • In which reaction does the oxidation number of oxygen increase?
    In the reaction \(2H_2O \to 2H_2 + O_2\), oxygen's oxidation number increases.
  • What must occur for oxidation to happen?
    Reduction must occur; oxidation cannot happen without reduction.
  • Which reaction will not occur as written: Mg (s) + Ca(OH)2 (aq) → Ca (s) + Mg(OH)2 (aq)?
    This reaction will not occur as written.
  • Correct expression for molarity?
    mmol solute/mL solution is a correct expression for molarity.
  • Which solution has the same moles of KCl as 75.00 mL of 0.250 M KCl?
    129.3 mL of 0.145 M KCl has the same moles.
  • Mass of KOH in 28.7 mL sample neutralized by 31.3 mL of 0.118 M HCl?
    Mass of KOH is 0.207 g.
  • Which requires the largest volume of 0.100 M NaOH for neutralization?
    10.0 mL of 0.0500 M phosphoric acid requires the largest volume.
  • Spectator ions in KOH (aq) + HNO3 (aq) reaction?
    K+ and NO3- are spectator ions.
  • Which are weak electrolytes among HNO3, HF, NH3, LiBr?
    HF and NH3 are weak electrolytes.
  • Which hydroxides are strong bases?
    Sr(OH)2, KOH, NaOH, and Ba(OH)2 are strong bases.
  • Which metals dissolve in aqueous nickel ion solution?
    Aluminum, chromium, barium, potassium dissolve; tin does not.
  • Concentration of NaCl solution from 9.3 g in 350 mL?
    Concentration is 0.45 M.
  • Molarity of glucose solution with 129 g in 200 mL?
    Molarity is 3.58 M.
  • Grams of NaCl in 55.0 mL of 1.90 M solution?
    There are 6.11 g of NaCl.
  • Concentration of iodide ions in 0.193 M barium iodide solution?
    Iodide ion concentration is 0.386 M.
  • Are any hydroxides weak bases among KOH, Ba(OH)2, RbOH, CsOH?
    None of these hydroxides are weak bases.
  • Which compound is soluble in water at 25 °C: AgNO3, Hg2Cl2, PbCl2, Ag2S, AgCl?
    AgNO3 is soluble in water at 25 °C.
  • Species where nitrogen has highest oxidation number?
    Nitrogen has highest oxidation number in NaNO3.
  • Moles of chloride ions in 0.500 L of 0.250 M AlCl3?
    There are 0.375 moles of chloride ions.
  • Molarity of acetic acid solution from 20.00 mL glacial acid diluted to 500.0 mL?
    Molarity is 0.699 M.
  • What increases internal energy of a system?
    Adding heat to the system increases internal energy.
  • Condition always increasing internal energy?
    System gains heat and has work done on it by surroundings.
  • Statement of the first law of thermodynamics?
    Energy lost by the system must be gained by the surroundings.
  • Is the reaction 4Al + 3O2 → 2Al2O3 exothermic or endothermic?
    It is exothermic and releases heat.
  • Heat absorption and ΔH sign for endothermic reaction?
    Endothermic reactions absorb heat and have a positive ΔH.
  • Calculate ΔE if system absorbs 12.4 J heat and does 4.2 J work on surroundings.
    ΔE = 8.2 J.
  • Heat released forming 155 g HBr with ΔH° = -72 kJ?
    Heat released is approximately 69 kJ.
  • Heat released when 29.5 g Cl2 reacts with excess H2 (ΔH° = -186 kJ)?
    Heat released is 77.4 kJ.
  • Specific heat (J/g-K) of substance with molar heat capacity 92.1 J/mol-K and molar mass 118 g/mol?
    Specific heat is 0.781 J/g-K.
  • Sign of work (w) when work is done on a system?
    Work done on a system has a positive value.
  • Work done (kJ) when volume expands from 19 L to 48 L against 2.5 atm?
    Work done is -7.3 kJ.
  • Heat released by reaction of 10.0 g Na2O2 with water (ΔH° = -126 kJ for 2 mol)?
    Heat released is approximately 8.08 kJ.