Which of the following will require the greatest energy input to separate the io

Question

Which of the following will require the greatest energy input to separate the ions? a. MgC_2 b. NaCl c. MgBr_2 d. MgI_2 e. MgF_2 Lanterns and stoves that use n-pentane as a fuel are often difficult to light on a cold day because the fuel has a low vapor pressure at low temperatures. Determine the vapor pressure of n-pentane on a night when the temperature is 0.0 degree C. The enthalpy of vaporization of n-pentane is 27.6 kJ/mol, and its boiling point is 36.0 degree C. a. 228 torr b. 209 torr c. 479 torr d. 185 torr e. 367 torr

Explanation / Answer

12. ANS: MgF2 will require highest energy to separate into its ions. It is beacause Mg2+ ion require first and second ionization enegies to form and highly electronegative character and small size of F- ion will be most difficult to remove from highly electropositive Mg2+ ion.

13. ANS: To find the vapor pressure at a given temperature,the Clausius-Clapeyron equation is used

: ln(P1/P2) = (Hvap/R)((1/T2) - (1/T1)).

T1 = 0oC = 273.15 K , T2 = 36oC = 309.15 K , Hvap = 27.6 kJ/mol = 27600 J/mol , R= 8.314 J/K.mol

P1 = pressure at T1= ?, P2= pressure at T2 = 1 atm

{ At boiling point of a liquid, its pressure become equal to atmospheric pressure.}

ln P1/P2 = (27600/ 8.314) [(1/309.15)-(1/273.15)] = 3319.7 (0.00323 - 0.00366)

ln P1 = -1.427

P1 = 0.24 atm = 0.24 x 760 = 183 torr

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