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Solutions. Chapter 2. What Is a Solution?. Solution is a mixture in which one or more substances are uniformly distributed in another substance i.e. plasma—liquid part of blood Parts of a solution Solute is substance dissolved in solution Solvent substance in which solute is dissolved
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Solutions Chapter 2
What Is a Solution? • Solution is a mixture in which one or more substances are uniformly distributed in another substance • i.e. plasma—liquid part of blood • Parts of a solution • Solute is substance dissolved in solution • Solvent substance in which solute is dissolved • Water is universal solvent
Concentration • Solutions may be made of various proportions of given solvent or solute • Concentration is measurement of amount of solute dissolved in fixed amount of solution • More solute dissolved greater concentration • Saturated solution refers to one in which no more solute can be dissolved
Aqueous Solution • Aqueous refers to solution in which water is solvent • Very important to living organisms • Marine microorganisms • Plants & acquisition of nutrients from soil • Body cells
Dissociation of Water • Force attraction between water molecules is so strong that oxygen atom of one water molecule can remove hydrogen atom from another water molecule • This breaks water molecule into 2 ions of opposite charge
Dissociation of Water • H2O H+ + OH- • OH- is known as hydroxide ion • Free H+ ion can react with another water molecule • H+ + H2O H3O+ • H3O+ is known as hydronium ion
Alkalinity & Acidity • Both alkalinity & acidity are a measure of the relative amounts of hydronium ions & hydroxide ions dissolved in a solution
Neutral Solution • Occurs if # of hydronium ions is equal to # of hydroxide ions • i.e. pure water
Acids • Solution is considered acidic if # of hydronium ions in solution is greater than # of hydroxide ions • Tend to have a sour taste • May be corrosive to some materials
Bases • Solution is considered basic if # of hydroxide ions in solution is greater than # of hydronium ions • Alkaline is synonymous to basic • Tend to have a bitter taste • Feel slippery
pH • pH scale • Scale compares relative concentrations of hydronium & hydroxide ions in a solution • Ranges from 0 to 14 • Scale is measured on logarithmic scale • Change of one pH unit reflects tenfold change in acidity or alkalinity • 0 to 6.99 acidic • 7 neutral • 7.01 to 14 basic
Buffers • Control of pH is important for living systems • Enzymes can function only within very narrow pH range • Buffers are chemical substances that neutralize small amounts of either an acid or base added to a solution