1 chapter 8 solutions 8.1 solutions the water lost from the body is replaced by the intake of fluids
TRANSCRIPT
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Chapter 8 Solutions
8.1 Solutions
The water lost from the body is replaced by the intake of fluids.
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Solute and Solvent
Solutions• are homogeneous
mixtures of two or more substances
• contain a solute, usually in smaller quantity
• contain a solvent, usually in greater quantity
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Solutes• spread evenly
throughout the solution
• cannot be separated by filtration
• can be separated by evaporation
• are not visible but can give a color to the solution
Nature of Solutes in Solutions
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Identify the solute in each of the following solutions:
A. 2 g of sugar (1) and 100 mL of water (2)B. 60.0 mL of of ethyl alcohol(1) and 30.0 mL of methyl alcohol (2)
C. 55.0 mL of water (1) and 1.50 g of NaCl (2)
D. Air: 200 mL of O2 (1) and 800 mL of N2 (2)
Learning Check
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Identify the solute in each of the following solutions:
A. 2 g of sugar (1)
B. 30.0 mL of methyl alcohol (2)
C. 1.5 g of NaCl (2)
D. 200 mL of O2 (1)
Solution
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Water• is the most common solvent• Draw a water molecule• Electronegativity is a measure of the
tendency of an atom to attract a bonding pair of electrons. The Pauling scale is the most commonly used. Fluorine (the most electronegative element) is assigned a value of 4.0, and values range down to caesium and francium which are the least electronegative at 0.7.
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Water• is the most common solvent• is a polar molecule• forms hydrogen bonds between the hydrogen
atom in one molecule and the oxygen atom in a different water molecule
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Formation of a Solution
Na+ and Cl ions• on the surface of a
NaCl crystal are attracted to polar water molecules
• in solution are hydrated as several H2O molecules surround each
Attractions in Solutions
Interactions between solutes and solvents that • are similar in polarity will form a solution • are not similar will not form a solution
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When NaCl(s) dissolves in water, the reaction can be written as
H2O
NaCl(s) Na+(aq) + Cl(aq)
solid separation of ions
Equations for Solution Formation
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Solid LiCl is added to water. It dissolves becauseA. the Li+ ions are attracted to the 1) oxygen atom ( -) of water
2) hydrogen atom ( +) of water
B. the Cl ions are attracted to the 1) oxygen atom ( -) of water 2) hydrogen atom ( +) of water
Learning Check
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Solid LiCl is added to water. It dissolves because
A. the Li+ ions are attracted to the
1) oxygen atom ( -) of water.
B. the Cl ions are attracted to the
2) hydrogen atom ( +) of water.
Solution
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Two substances form a solution • when there is an attraction between the
particles of the solute and solvent
• when a polar solvent such as water dissolves polar solutes such as sugar and ionic solutes such as NaCl
• when a nonpolar solvent such as hexane (C6H14) dissolves nonpolar solutes such as oil or grease
Like Dissolves Like
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Like Dissolves Like
Solvents Solutes
Water (polar) Ni(NO3)2
CH2Cl2(nonpolar) (polar)
I2 (nonpolar)
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Will the following solutes dissolve in water? Why?
1) Na2SO4
2) gasoline (nonpolar)
3) I2
4) HCl
Learning Check
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Will the following solutes dissolve in water? Why?
1) Na2SO4 Yes, the solute is ionic.
2) gasoline No, the solute is nonpolar.
3) I2 No, the solute is nonpolar.
4) HCl Yes, the solute is polar.
Most polar and ionic solutes dissolve in water because water is a polar solvent.
Solution
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Solutions Continued
Properties of Solutions
Ethylene glycol is added to a radiator to form a aqueous solution that has a lower freezing point than water.
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Solutions
Solutions • contain small particles (ions or
molecules) that are uniformly dispersed in the solvent
• are not separated by filters or a semipermeable membrane
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Colloids
Colloids• contain large solute particles
that are uniformly dispersed in the solvent
• cannot be separated by filtration • can be separated by
semipermeable membranes
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Suspensions
Suspensions• have very large particles that
settle out • are separated by filters • must be stirred to stay
suspended
Examples: blood platelets, muddy water, and calamine lotion