8. Solution ChemistryA solution is a mixture of two or more compounds in variable proportions.

The compound in the higher amount is called the solvent.The other compound(s) are called solutes.

Like dissolves Like

ElectrolytesA compound that produces ions when it dissolves in water is an electrolyte

Strong Electrolytes – fully dissociate in solution ……e.g. soluble ionic compounds

NaCl (s) (add water) → Na+(aq) + Cl-

(aq).

strong acid HCl (added to water) → H+(aq) + Cl-

(aq).

Weak electrolytes – partially dissociate in solution ……e.g. weak acids

CH3-COOH (added to water) ↔ H+(aq) + CH3-COO-

(aq).

acetic acid proton acetate ion.

nonelectrolytes – may dissolve but do not “ionize” in aqueous solution.

e.g. Glucose(s) (add water) ↔ Glucose(aq)

Concentration - A measure of how much solute is dissolved

Units (general) - amount of solute amount of solution

Molarity (M) - moles of solute or mol/L Liter of solution

Milliequivalents per Liter (meq/L) - milliequivalents of solute Liter of solution

this is the same as millimoles/L or mmol/L or mM for ±1 ions for ±2 ions the [ ] in mM is ½ x the meq/L etc.

% (w/v) - ___g of solute___ 100 ml of solution (which is ~ 100 g for water)

Parts per million ppm

&

Parts per billion ppb

… or 138 mM or 0.138 M … or 5 mM or 0.005 M

… or 4 meq/L • 1 mmol/2 meq = 2 mM or 0.002 M

… or 110 mM or 0.110 M … or 30 mM or 0.030 M … or 2 mM or 0.002 M

Practice Problems (page 267) Keep track of units!

7.24 What is the Molarity of 750 ml of solution containing 2.10 moles Na2SO4?

7.26 What is the Molarity of 500 ml of solution containing 45 g NaHCO3?

750 ml = 0.750 L

2.10 moles Na2SO4 = 2.8 M 0.750 L

500 ml = 0.500 L

45 g NaCO3 • 1 mol NaCO3 = 1.07 M 0.500 L 84 g

Problem 8.20 on page 320

8.20 A .0 5% dextrose IV fluid contains 35meq/L of K+. A patient gets 235ml of this IV solution.

How many moles of K+ did they receive? (note: since K+ charge is 1 then meq = mM)

Dextrose is D-glucose

How many grams of glucose did the patient in problem 7.20 receive?

5.0 g glucose • 235 ml = 11.75 g 100 ml

What is the molarity of the solution in problem 7.20? 100 ml = 0.100 L

5.0 g glucose • 1 mol glucose = 0.28 M glucose 0.100 L 180 g

What is the w/v of NaCl that corresponds total electrolyte concentration of blood plasma? (= 154 mM or 0.154 M)

0.154 mol NaCl • 58.5 g NaCl • 0.1 L = 0.90 g NaCl = 0.90 % (m/v) 1 L 1 mol 100 ml 100 ml soln

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8.5 Dilution

• One way to prepare solutions of lower concentration is to dilute a solution of higher concentration by adding more solvent.

Dilution Calculations

In a lab solutions are often prepared at a higher concentration than they are used.The higher concentration solution is often referred to as the stock solution.The solution required is prepared from the stock solution by dilution.Dilutions always use the following equation …..

C1V1 = C2V2

C = concentration (any units may be used as long as they match on both sides of the equation)

V = Volume (any units may be sued as long as they match on both side of the equation)

1 = stock solution 2 = diluted solution

Practice Problems (page 270)

7.38 How many ml of a 0.90% (m/v) NaCl solution can be prepared from 600 ml of a 9.0% (m/v) stock solution?

7.40 If 40 ml of a 6.0 M NaOH solution is diluted to a final volume of 200 ml,what is the resulting concentration of the solution?

a) 30 M b) 1.0 M c) 0.8 M d) 1.2M

C1V1 = C2V2

7.42 How would you prepare 2 L of 1 M MgCl2 from a 5M MgCl2 stock solution?

Homework for Friday

7.587.667.687.707.747.847.86

Osmosis and diffusion

A solution is a homogeneous mixture.

If you ‘tracked’ one solute molecule/ion in a solution over time, which of the following would you observe? a) the solute molecule would stay in the same place. b) the solute molecule would gradually move in a very random fashion. c) the solute molecule would slowly move but always in the same direction. d) the solute molecule would rapidly move through the solution in straight lines.

The motion of a solute in a solution is called Brownian motion.

Diffusion occurs when a fluid has and unequal distribution of a solute, and it moves to make the distribution uniform (or equal).

Diffusion requires a change in concentration over time and proceeds until the fluid becomes a homogeneous solution. (e.g. a drop of food coloring in a beaker diffuses until the beaker has a uniform distribution of color)

Diffusion A solute is in a solution separated by a membrane. The pores in the membrane are larger than the solute. What will happen?

Diffusion – particles will move from an area of high concentration to lower concentration.

Osmosis A solute is in a solution separated by a membrane. The solute particles are larger than the pores. What will happen to the solute molecules? What about the solvent molecules? (not pictured)

Osmosis – solvent particles will move from an area of high solvent concentration to lower solvent concentration. Or from an area of low [solute] to high [solute].

Solvent flow

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Osmosis and Diffusion

Colloidal particles are evenly distributed.Particle sizes range from 1 nm → 1 mm.Particles stay dispersed and don’t settle.

e.g. protein solutions

Colloidal Dispersion

Blood Plasma contains large amounts of the protein Serum Albumin (and other proteins). The [protein] in blood is > [protein] in interstitial fluid (the fluid between cells).This creates COP (colloidal osmotic pressure).

The pumping action of the heart also produces a hydrostatic pressure that opposes COP.

HP > COPFluid flows into cells carrying O2 & nutrients

HP < COPFluid flows into veins carrying CO2 & waste

Cells of various tissues Arterial capillary

flow

Venouscapillary

flow

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Dialysis• The kidneys act to remove small waste molecules out of the blood

through diffusion across membranes in the kidneys. • A person whose kidneys are failing can undergo artificial dialysis

—called hemodialysis—to cleanse the blood. • In this process, blood is removed from the patient

and passes through one side of a semipermeable membrane in contact on the opposite side with an isotonic dialyzing solution.

• Urea and small waste molecules diffuse outof the passing blood and into the dialyzing solution, and the dialyzed blood returns to the patient.

Ions, nonpolar molecules, and polar molecules move across cell membranes using diffusion, facilitated transport, or active transport.

•

How does • get into cell?

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Transport across Cell Membranes• Small molecules like water and the

nonpolar molecules O2, N2, and CO2 can diffuse directly through the cell membrane.

• Diffusion moves solutes to equalize the concentrations on either side of a membrane.

• This process does not require any additional energy so is also referred to as passive diffusion.

• Other nonpolar molecules like steroids can also passively diffuse through cell membranes.

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Transport across Cell Membranes

• Molecules like ions and glucose molecules require the help of membrane proteins to cross the membrane (facilitated transport)

• Such proteins are referred to as transporters or channels.

• Active transport requires energy consumption (ATP).

Chapter 8 SummarySolutions Are Mixtures

Substances that release ions when they dissolve in waterare called electrolytes because the solution will conductan electrical current. (strong vs. weak)

The concentration of a solution is the amount of solute dissolvedin a certain amount of solution. Fluid replacement solutions are often expressed in units of mEq/Lor in some cases mmol/L. Molarity is the moles of solute per liter of solution. Percent mass/volume {%(m/v)} expresses the ratio of the mass of solute (in g)to the volume of solution (in mL) multiplied by 100. %(m/v) is equivalent to the unit g/dL. (1 dL = 100 ml)

Osmosis and Diffusion

Transport across Cell MembranesC1V1 = C2V2