知到答案Basic Chemistry 基础化学智慧树答案_2022年

第八章

A solution is prepared by dissolving 15.0 g of NH3 in 250 g of water. The density of the resulting solution is 0.974 g/mL. The mole fraction of NH3 in the solution is __________.
0.0597
16.8
0.94
0.922
答案:0.0597
The vapor pressure of pure water at 25 °C is 23.8 torr. Determine the vapor pressure (torr) of water at 25 °C above a solution prepared by dissolving 35 g of urea (a non-volatile, non-electrolyte, MW = 60.0 g/mol) in 75 g of water.
27
2.9
21
0.88The freezing point of ethanol (C2H5OH) is -114.6 °C. The molal freezing point depression constant for ethanol is 2.00 °C/m. What is the freezing point (°C) of a solution prepared by dissolving 50.0 g of glycerine (C3H8O3 a nonelectrolyte) in 200 g of ethanol?
-115
-120
-132.3
-5.42A solution is prepared by dissolving 6.00 g of an unknown nonelectrolyte in enough water to make 1.00 L of solution. The osmotic pressure of this solution is 0.750 atm at 25.0 °C. What is the molecular weight (g/mol) of the unknown solute?
16.4
195
110
5.12 × 10-3The principal reason for the extremely low solubility of NaCl in benzene (C6H6) is the __________.
strength of the covalent bond in NaCl
weak solvation of Na+ and Cl- by C6H6
increased disorder due to mixing of solute and solvent
hydrogen bonding in C6H6Pairs of liquids that will mix in all proportions are called __________ liquids.
supersaturated
unsaturated
miscible
saturatedThe solubility of oxygen gas in water at 25 °C and 1.0 atm pressure of oxygen is 0.041 g/L The solubility of oxygen in water at 3.0 atm and 25 °C is __________ g/L.
0.31
0.014
3
0.12A sample of potassium chlorate (15.0 g) is dissolved in 201 g of water at 70 °C with precautions taken to avoid evaporation of any water. The solution is cooled to 30.0 °C and no precipitate is observed. This solution is __________.
supersaturated
hydrated
miscible
unsaturatedThe concentration of lead nitrate (Pb(NO3 )2) in a 0.726 M solution is __________ molal. The density of the solution is 1.202 g/mL.
0.476
1.928
0.755
0.65The concentration of a benzene solution prepared by mixing 12.0 g C6H6 with 38.0 g CCl4 is __________ molal.
0.508
0.316
0.622
4.04