# 急!!!! 徵求化學解答

6) Which of the following can be interpreted as a measure of randomness?

A) free energy B) entropy C) temperature D) enthalpy

6)

7) What mass of dinitrogen monoxide, N2O, contains the same number of molecules as 3.00 g of

trichlorofluoromethane, CCl3F?

A) 9.37 g B) 0.961 g C) 0.106 g D) 1.04 g

7)

8) What mass of sulfur hexafluoride, SF6, has the same number of fluorine atoms as 25.0 g of oxygen

difluoride, OF2?

A) 22.5 g B) 8.33 g C) 0.901 g D) 203 g

8)

9) How many chloride ions are in 1.50 mol of aluminum chloride?

A) 3.00 chloride ions B) 4.50 chloride ions

C) 2.71 &times; 1024 chloride ions D) 9.03 &times; 1023 chloride ions

9)

10) How many anions are in 0.500 g of MgBr2?

A) 2.22 &times; 1026 anions B) 3.27 &times; 1021 anions

C) 1.64 &times; 1021 anions D) 4.43 &times; 1026 anions

10)

2

Rating

6) B)

It is a basic concept in thermodynamics that entropy is a measure of randomness.

7) B)

Molar mass of N2O = 14.01x2 + 16 = 44.02 g/mol

Molar mass of CCl3F = 12.01 + 35.45x3 + 19 = 137.36 g/mol

No. of moles of CCl3F molecules = 3/137.36 = 0.02184 mol

No. of moles of N2O molecules = 0.02184 mol

Mass of N2O = 0.02184 x 44 = 0.961 g

8) A)

Molar mass of SF6 = 32.06 + 19x6 = 146.06 g/mol

Molar mass of OF2 = 16 + 19x2 = 54 g/mol

No. of moles of OF2 molecules = 25/54 = 0.463 mol

No. of moles of F atoms in OF2 = 0.463 x 2 = 0.926 mol

No. of moles of F atoms in SF­6 = 0.926 mol

No. of moles of SF6 molecules = 0.926/6 = 0.1543 mol

Mass of SF6 = 0.1543 x 146.06 = 22.5 g

9) C)

Each mole of AlCl3 contains 3 mol of Cl^- ions.

No. of moles of AlCl3 = 1.50 mol

No. of moles of Cl^- ions = 1.50 x 3 = 4.50 mol

No. of Cl^- ions = 4.50 x (6.023 x 10^23) = 2.71 x 10^24 Cl^- ions

10) B)

Molar mass of MgBr2 = 24.31 + 79.9x2 = 184.11 g/mol

Each mole of MgBr2 contains 2 moles of Br^- anions.

No. of moles of MgBr2 = 0.5/184.11 = 0.002716 mol

No. of moles of Br^- anions = 0.002716 x 2 = 0.005432 mol

No. of Br^- anions = 0.005432 x (6.023 x 10^23) = 3.27 x 10^21 Br^- anions