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Regents Chemistry Exam Review: Acids, Bases and Salts

Acid and base definitions

Arrhenius Definition:

Acid yields H+ (hydrogen ions) when dissolved in water.

Base yields OH- (hydroxide ions) when dissolved in water.

Bronsted-Lowry definition:

Acid is a proton (H+) donor

Base is a proton (H+) acceptor

There are three tables on the Reference table that are used for the acid and bases topic. Let's look at them.

Table K lists all the common acids that you may encounter on your Regents exam. Table L lists all the common bases that may be encountered on the exam.

Table M on the Reference Table shows a list of indicators and the pH range at which their colors change.

Let's take a look at methyl orange for example. Methyl orange has a pH range of 3.1–4.4 and color change of red to yellow. This means that if the solution's pH is lower than 3.1, the color will be red and above 4.4 the color will be yellow.


Titration is a laboratory technique that is used to find the molarity of an unknown acid or base. During this procedure a known base is added to unknown acid (or vice versa) until an indicator changes its color (endpoint).

In titration an acid and a base will neutralize each other when moles of H+ will be equal to the moles of OH-.

The formula that is used in titration calculations can be found in Table T.

MaVa = MbVb where Ma = molarity of H+ (acid)

Mb = molarity of OH– (base)

Va = volume of acid

Vb = volume of base

pH scale

pH scale indicated the acidity or basicity of a solution. It is from 0 to 14. pH less than 7 is acidic. pH of 7 is neutral. pH higher than 7 is basic. The lower the pH the more acidic the solution is and the higher the concentration of H+ (and lower of OH-). The higher the pH the the more basic the solution is and the higher the concentration of OH- (and lower of H+). Each pH unit change will change the concentration by a factor of 10. For example, going from pH=5 to pH=6 increases the concentration of OH- by 10. Going from pH=7 to pH=5 increases the concentration of H+ by 100 (10*10).

Facts to remember:

  • The reaction between an acid and a base produces water and salt. This reaction is called neutralization reaction.

  • An electrolyte is a substance that can conduct electricity when dissolved in water.

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