Health Occupations Entrance Exams: Third Edition by LearningExpress LLC

Author:LearningExpress LLC [LLC, LearningExpress]
Language: eng
Format: epub
Tags: ebook, epub, Health occupations examination questions
Publisher: LearningExpress, LLC
Published: 2013-09-20T04:00:00+00:00

Hydrochloric (HCl)

Hydrobromic (HBr)

Hydroiodic (HI)

Perchloric (HClO4)

Sulfuric (H2SO4)

Bases are proton acceptors (Bronsted) or electron donors (Lewis). When dissolved in water, strong bases such as NaOH dissociate to release hydroxide ions and sodium cation. Bases have a bitter taste and feel slippery like soap.

2. Reactions of Acids

Common reactions include:

• metal + acid → salt + hydrogen Zn + 2HCl → ZnCl2 + H2↑

• base + acid → salt + water NaOH + HNO3 → NaNO3 + H2O

• metal oxide + acid → salt + water CaO + 2HNO3 → Ca(NO3)2 + H2O

• metal carbonate + acid → salt + carbonic acid (unstable) NaHCO3 + HCl → NaCl + H2CO3 (H2CO3 → H2O + CO2↑)

3. Autoionization of Water

In pure water, 2H2O ⇆ H3O+ + OH–.

The molar concentration of H3O+ is equal to molar concentration of OH– (i.e., [H3O]+ = [OH–]).

The ion product of water is Kw; Kw = [H3O+] × [OH–] = 1 × 10–14. Thus, in pure water: [H3O+] = [OH–] = 1 × 10–7 moles/liter.

4. pH

pH = – log [H+] The pH measures the negative logarithm (for presentation of very small numbers in a large scale) of the hydrogen ion concentration (in moles/liter). The pH scale runs from 0 to 14 with acids in the lower end of the scale (smaller than pH 7), whereas bases are at the higher end (greater than pH 7).

5. Buffers

Buffer is a solution of a weak base and its conjugate acid (weak also) that prevents drastic changes in pH. The weak base reacts with any H+ ions that could increase acidity, and the weak conjugate acid reacts with OH– ions that may increase the basicity of the solution.

a. Carbonic Acid/Bicarbonate Buffer

The pH of blood plasma must be maintained at pH 7.40 by a buffer system consisting of the couple H2CO3 and HCO3–.

Neutralization of acid: HCO3– + H+ → H2CO3

Neutralization of base: H2CO3 + NaOH → NaHCO3 + H2O

b. Phosphate Buffer

The principal buffer system inside cells consists of the couple [H2PO4– and HPO4–2.]

Neutralization of acid: HPO4–2 + H+ → H2PO4–

Neutralization of base: H2PO4– + OH– → HPO4–2 + H2O

6. Titration

Titration is a technique used to determine the unknown concentration of an analyte of interest by reacting it with a known quantity of a reagent. In an acid–base titration, an acid or base of unknown concentration is reacted with a known amount of base or acid.

a. Equivalence Point

In an acid–base titration, the equivalence point is reached when the amount of titrant (acid or base of known concentration) is equal to the amount of analyst (base or acid of unknown concentration), and the solution is of neutral pH.

b. Normality (N)

Normality is the number of equivalents of the solute per liter of solution. 1 N solution of acid (or base) contains 1 equivalent of an acid (or base) per liter of solution.

You Should Review

• monoprotic, diprotic, and triprotic acids

• organic and inorganic acids

• Arrhenius acids and bases

• Bronsted-Lowry acids and bases

• reactions of acids

• activity series of metals

• solubilities of salts

• ionic equations

• buffer systems in the body

• metabolic acidosis and alkalosis

• respiratory acidosis and alkalosis

Questions

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