Question
Categorize (1) milk, (2) whipped cream and (3) fog as emulsion, foam or aerosol.
Answer:
Milk is an emulsion (liquid in liquid), whipped cream
... [Show More] is a foam (gas in liquid) and fog is
an aerosol (liquid in gas).
Question 2
Water (H2O) with a molecular weight of 18 has a boiling point of 100oC and methane
(CH4) with a somewhat similar molecular weight of 16 has a boiling point of -161oC. This
difference is much higher than can be explained by the polarity of water. Explain what
causes this difference.
Answer:
Hydrogen bonds which are strong intermolecular attractive forces form between water
molecules requiring much more energy to separate the molecules than for other
molecules.
Question 3
Rank and explain how the freezing point of 0.100 m solutions of the following ionic
electrolytes compare. List from lowest freezing point to highest freezing point.
GaBr3, CaCl2, KCl, Ca3(PO4)2
Answer:
GaBr3 → Ga+3 + 3 Br-
∆tf = 1.86 x 0.1 x 4 = 3rd lowest
FP
CaCl2 → Ca+2 + 2 Cl-
∆tf = 1.86 x 0.1 x 3 = 2nd
lowest FP
KCl → K+
+ Cl-
∆tf = 1.86 x 0.1 x 2 = highest
FP
Ca3(PO4)2 → 3 Ca+2 + 2 PO4
-3 ∆tf = 1.86 x 0.1 x 5 = lowest FP
FP: Ca3(PO4)2 < GaBr3 < CaCl2 < KCl
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Question
Show the calculation of the mass percent solute in a solution of 20.8 grams of
Ba(NO3)2 in 400 grams of water. Report your answer to 3 significant figures.
Answer:
Mass % = (gsolute / gsolute + gsolvent) x 100%
Mass % = (20.8 / 20.8 + 400) x 100 = 4.94%
Question 5
Show the calculation of the molality of a solution made by dissolving 28.5 grams of
C8H16O8 in 400 grams of water. Report your answer to 3 significant figures.
Answer:
molality = (gsolute / MW) / (gsolvent / 1000)
molality = (28.5 / 240.208) / (400 / 1000) = 0.297 m
Question 6
Show the calculation of the molarity of a solution made by dissolving 35.9 grams of
Mg(NO3)2 to make 400 ml of solution. Report your answer to 3 significant figures.
Answer:
Molarity = (gsolute / MW) / (mlsolvent / 1000)
Molarity = (35.9 / 148.325) / (400 / 1000) = 0.605 M
Question 7
Show the calculation of the mass of Ba(NO3)2 needed to make 250 ml of a 0.200 M
solution. Report your answer to 3 significant figures.
Answer:
Molarity = (moles) / (mlsolvent / 1000) [Show Less]