-14. The coacentration unit of molaly is symbolized as a. M d. mol c. AM Determi
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-14. The coacentration unit of molaly is symbolized as a. M d. mol c. AM Determine the molal concentration of a sugar solution in water that has a freezing point of -2 1C K 186 C m for water I5. 1.13 m b. 1.13 c. 3.91 d. -3.91 m e 0.113 m /1. The normal temperature range of the liq nd phase of the e idstateCoiorc which of the following solutions will have the largest temperature range for the liquid state? a. 1 Maqueous ethanol solution b. I Maqucous potassium bromide solution e 1Maqucous magnesium sulfate c. 1 Maqueous acetic acid solution d. 1 Maqueous magnesium bromide solution solution frin v17. What would be the freezing point of a l m solution of 11a in water (K-186.0? a. 000 d. 186°C e.4M-C 1.61.2.1-3.72 1842 1 3.72 -093 c -3.72C 18. A solution is made by dissolving 100 g of essentially monvolatile ethylene glycol (CallO) in 500 g of water. what is the resulting freezing point of the solution (Kr 860m)? a. -599 c, -0.372°C -323 e. 19 19. A newspaper article suggested using a fertilizer such as ammonium sulfate or ammonium nitrate to lower the melting poin of the following compounds would give the largest freezing point depression when 100 g of the compound are dissolved in I kg of solvent? a. NH NOs (80.1 g'mol) b. (NHSO4 (132.1 g/mol) c. MgSO. (120.4 gmol) nt of ice on sidewalks because many of the deicing salts can damage lawns and sidewalks. Which d. CaCh (1110 g/mol) e MgCl: (95.2 gmol) What is the molality of a solution produced by dissolving 14.40 g of Lia (42.39 g mol) in water to make 0.104 L of solution with a density of 1.102 giml? a. 0.340 m b. 3.39 m c. 3.27 m d. 3.74 m e. 2.96 m freezing point? 21. Which of the following aqucous solutions will have the lowest freezing poiat? d. 0.04 m sodium sulfate, Na SO4 e. 0.05 m sodium chloride, NaCl a. 0.1 m magnesium sulfate, MgSO b. 0.1 m potassium chloride, KCI c 0.08 m magnesium chloride, MgClExplanation / Answer
14. The units of molality is m. The units is called molal and denoted as m. Answer is b.
15. Freezing point of solution = -2.1 oC
Freezing point of water = 0.0 oC
Depression in freezing point = 0.0-(-2.1) = 2.1 oC
Kf of water 1.86 oC/m
Molality = depression in freezing point/Kf = 2.1/1.86 = 1.13 m
Answer is a.
16. Temperature range means difference in melting and boiling point.
Out of the given compounds, the KBr has an ionic bond, so it does not boil easily. Other compounds are also acids, but hte ionic bond is not that strong. So, answer is KBr. Answer is b.
17. Molality = 1 m
Kf = 1.86 oC/m
So, depression in freezing point = Kf.m = 1.86*1 = 1.86 oC
Freezing point of water = 0.00 oC
So, freezing point of solution = 0.00-1.86 = -1.86 oC
Answer is b.
18. Mass of ethylene glycol = 100 g
Molar mass of ethylene glycol = 62 g/mol
Moles of ethylene glycol = mass/molar mass = 100/62 = 1.61 mol
Mass of water = 500 g = 0.500 kg
Molality = moles/mass of water = 1.61/0.500 = 3.22 m
Kf of water = 1.86 oC/m
Depression freezing point = Kf.m = 3.22*1.86 = 6.00 oC
Freezing point of solution = 0.00-6.00 = -6.00 oC
Answer is a.
19. Depression in freezing point = Kf.m
M = moles/molar mass
So, Depression in freezing point = Kf.mol/molar mass
Depression in freezing point is inversely proportional to molar mass
More the mass, less in dpression in freezing point.
So, out of given compounds, (NH4)2SO4 has highest molar mass, so the freezing point of the solution would be highest.
Answer is b.
20. Volume of solution = 0.104 L = 104 ml
Density of solution = 1.102 g/ml
Mass of solution = density*volume = 104*1.102 = 114.6 g
Mass of solute = 14.40 g
Mass of solvent = mass of solution-mass of solute = 114.6-14.40 = 100.21 g = 0.100 kg
Molality = moles of LiCl/mass of solute = 14.40/(42.39*0.100) = 3.39 m
Answer is b.
21. Depression in freezing point is directly proportional to molality
Higher the molality, higher is freezing point depression, lower is freezing point of solution.
Out of the given solutions, a and b have same values. But i of KCl is 1 and of MgSO4 is 2.
So, MgSO4 will have lowest freezing point. Answer is a.
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