A solution is prepared by dissolving 0.117 moles of sucrose, C_12H_22O_11, in 13

Question

A solution is prepared by dissolving 0.117 moles of sucrose, C_12H_22O_11, in 13.87 moles of water at 25 degree C. What is the vapor pressure of the solution if the vapor pressure of water at 25 degree C is 23.76 mm Hg? A) 0.198 mm Hg B) 20.5 mm Hg C) 23.6 mm Hg D) 24.0 mm Hg E) 27.2 mm Hg A 0.668 g sample of an unknown gas occupies 218 mL at 398 K and 1.41 atm. What is the identity of the gas? A) F_2 (MM = 38.0 g/mol) B) Cl_2 (MM = 70.90 g/mol) C) Br_2 (MM = 159.8 g/mol) D) l_2 (MM = 253.8 g/mol) E) greaterthanorequalto (MM = 72.63 g/mol)

Explanation / Answer

3 ) C) 23.6 mm Hg

Moles sucrose = 0.117
Moles water = 13.87

Mole fraction water = X =13.87 / 13.87 + 0.117=13.87 /13.987 =0.9916

p = p°X ( Raoult's law)

p = 23.76 x 0.9916 =23.6 mm Hg

4) B) Cl2 (MM =70.90 g/mol)

Moles gas,n = PV/RT =1.41 atm x 0.218 L /0.08206 L.atm.mol-1k-1 x 398 K

=0.30738 /32.65988

=0.0094115

Molar mass = 0.668 g /0.0094115 mol =70.90 g/mol

So the gas will be Cl2.

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