Electrolyte Concentrations

Electrolytes are important for their chemical, physical (osmotic), and electrical effects on the body. Their electri-

9Amedeo Avogadro (1776-1856), Italian chemist

Table 2.4 Types of Mixtures

Solution

Colloid

Suspension

Particle size

< 1 nm

1-100 nm

>100 nm

Appearance

Clear

Often cloudy

Cloudy-opaque

Will particles settle out?

No

No

Yes

Will particles pass through a selectively

permeable membrane?

Yes

No

No

Examples

Glucose in blood

Proteins in blood

Blood cells

O2 in water

Intracellular fluid

Cornstarch in water

Saline solutions

Milk protein

Fats in blood

Sugar in coffee

Gelatin

Kaopectate

Saladin: Anatomy & I 2. The Chemistry of Life I Text I I © The McGraw-Hill

Physiology: The Unity of Companies, 2003 Form and Function, Third Edition

Differences Solution And Suspension
  • b) 0.1 M glucose 0.1 M sucrose
  • 18 g/L) (34 g/L)

Figure 2.11 Comparison of Percentage and Molar Concentrations. (a) Solutions with the same percentage concentrations can differ greatly in the number of molecules per volume because of differences in molecular weights of the solutes. Fifty grams of sucrose has about half as many molecules as 50 g of glucose, for example. (b) Solutions with the same molarity have the same number of molecules per volume because molarity takes differences in molecular weight into account.

  • b) 0.1 M glucose 0.1 M sucrose
  • 18 g/L) (34 g/L)

Figure 2.11 Comparison of Percentage and Molar Concentrations. (a) Solutions with the same percentage concentrations can differ greatly in the number of molecules per volume because of differences in molecular weights of the solutes. Fifty grams of sucrose has about half as many molecules as 50 g of glucose, for example. (b) Solutions with the same molarity have the same number of molecules per volume because molarity takes differences in molecular weight into account.

cal effects, which determine such things as nerve, heart, and muscle actions, depend not only on their concentration but also on their electrical charge. A calcium ion (Ca2+) has twice the electrical effect of a sodium ion (Na+), for example, because it carries twice the charge. When we measure electrolyte concentrations, we must therefore take the charges into account.

One equivalent (Eq) of an electrolyte is the amount that would electrically neutralize 1 mole of hydrogen ions (H+) or hydroxide ions (OH-). For example, 1 mole (58.4 g) of NaCl yields 1 mole, or 1 Eq, of Na+ in solution. Thus, an NaCl solution of 58.4 g/L contains 1 equivalent of Na+ per liter (1 Eq/L). One mole (98 g) of sulfuric acid (H2SO4) yields 2 moles of positive charges (H+). Thus, 98 g of sul-furic acid per liter would be a solution of 2 Eq/L.

The electrolytes in our body fluids have concentrations less than 1 Eq/L, so we more often express their concentrations in milliequivalents per liter (mEq/L). If you know the millimolar concentration of an electrolyte, you

Chapter 2 The Chemistry of Life 67

can easily convert this to mEq/L by multiplying it by the valence of the ion:

1 mM Na+ = 1 mEq/L 1 mM Ca2+ = 2 mEq/L 1 mM Fe3+ = 3 mEq/L

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  • madonna
    What are electrolyte concentrations?
    1 year ago

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