Online Exam - Chem2 | Me.Committee

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Online Exam - Chem2 | Me.Committee

#لجنة_الهندسة_الميكانيكية #الفريق_الأكاديمي. . . R = 8. 314 J/mol >>>> K =0. 0821 L. Atm/mol. K


Questions and Answers
  • 1. 
    Constants >>> R = 8.314 J/mol   >>>>  K =0.0821  L.atm/mol.k ... Q1) The equilibrium constant for the following reaction is 5.0 × 10at 25°  C , the value of Δ G  (KJ/mol) for this reaction is : N2(g) + 3H(g) ⇆ 2NH3(g)
    • A. 

      22

    • B. 

      -4.2

    • C. 

      -25

    • D. 

      -50

  • 2. 
    Q2) The rate constant (s−1) of a first order that has  half life of (225 s)  is
    • A. 

      0.693

    • B. 

      3.08 × 10-3

    • C. 

      1.25

    • D. 

      12.5

  • 3. 
    Q3) As a temperature of a reaction is increased , the rate of the reaction increases because : 
    • A. 

      Reactant molecules collide less frequently

    • B. 

      Activation energy is lowered

    • C. 

      Reactant molecules collide more frequently and with greater energy per collision

    • D. 

      Reactant molecules collide less frequently and with greater energy per collision

  • 4. 
    Q4) why is potassium bromide (KBr) is insoluble in carbon tetrachloride (CCl4) ?
    • A. 

      Both KBr and (CCl4) are non polar

    • B. 

      Solvent -solvent interaction are strong

    • C. 

      Solute -solvent interaction are strong

    • D. 

      Solute -solvent interaction are weak

  • 5. 
    Q4) In general , as temperature increases , reaction rate 
    • A. 

      Increases , if the reaction is exothermic

    • B. 

      Increases , if the reaction is endothermic

    • C. 

      Increases , regardless whether the reaction is endothermic or exothermic

    • D. 

      Stays the same if the reaction is first order

  • 6. 
    Q5) For the elementary reaction NO3 + CO → NO2 + CO2 the molecularity and the rate law of the reaction are : 
    • A. 

      2, K [NO3] [CO]

    • B. 

      4, K [NO3] [CO] [NO2] [CO2]

    • C. 

      2, K [NO2] [CO2]

    • D. 

      2, K [NO3] [CO] / [NO2] [CO2]

  • 7. 
    The reaction A(aq) → B(aq) is first order in [A]  . A solution is prepared with [A] = 1.22 M . The following data is obtained as the reaction proceeds . The rate constant (s−1)  for this reaction is : Time (s) 0.0 6.0 12.0 18.0 [A] (M) 1.22 0.61 0.31 0.15
    • A. 

      0.23

    • B. 

      1.0

    • C. 

      0.17

    • D. 

      0.12

  • 8. 
    Q8) A compound decomposes by a first-order process . If 25.0% of the compound decomposes in 60.0 minutes , the half-life of the compound is :
    • A. 

      65

    • B. 

      120

    • C. 

      145

    • D. 

      180

  • 9. 
    Q9) which of the units below are appropriate for a second-order reaction rate constant 
    • A. 

      Ms−1

    • B. 

      S−1

    • C. 

      Mol/L

    • D. 

      M−1  s−1

  • 10. 
    Q10) A certain second order reaction is 60% complete in 25 minutes . calculate the rate constant (K) of this reaction :
    • A. 

      6.0 × 10^-2

    • B. 

      2.7 × 10^-2

    • C. 

      3.3 × 10^-4

    • D. 

      2.1 × 10^-2

  • 11. 
    Q11) A sealed 1.0 L flask is charged with 0.500 mol of  I2  and 0.500 mol of  Br2  . An equilibrium reaction ensues :   I(g) + Br2 (g)  ⇆  2 IBr (g) when te container contents achieve equilibrium , the flask contains 0.84 mol of IBr . Keq is:  
    • A. 

      11

    • B. 

      4.0

    • C. 

      110

    • D. 

      6.1

  • 12. 
    Q12) which is true at equilibrium ?
    • A. 

      The limiting reagent has been consumed

    • B. 

      The rates of the forward and reverse reactions are equal

    • C. 

      The rate constants of the forward and reverse reactions are equal

    • D. 

      The value of the equilibrium constant is 1

  • 13. 
    Q13) Given the following reaction at equilibrium at 450.0° C : CaCO3 (s) ⇆  CaO (s) + CO2 If pCO2 = 0.0160 atm , then    Kc =
    • A. 

      0.0160

    • B. 

      0.0821

    • C. 

      7.23

    • D. 

      2.7 × 10-4

  • 14. 
    Q14) The following data were obtained for the reaction  BF3 + NH3 →  F3BNH3   Exp [BF3] [NH3] initial rate 1 0.25 0.25 0.213 2 0.25 0.125 0.1065 3 0.50 0.125 0.1065 the rate law of the reaction is :
    • A. 

      K [NH3]

    • B. 

      K [BF3]

    • C. 

      K [BF3] [NH3]

    • D. 

      K [NH3]^5

  • 15. 
    Q15) For the previous question , what is the rate when [BF3] =( 0. 10) , [NH3]= 0.50 M ?
    • A. 

      0.426

    • B. 

      0.50

    • C. 

      0.852

    • D. 

      1.0

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