pH,Acidic and Basic Solutions

Acids

• Acids are substances that release positively charged hydrogen ions, H+, in the water.

• H+ will combine with water releasing a positively charged ion called hydronium (H3O)+

HCl + H2O -----> (H3O)+ + Cl-

Bases

• Bases are substances that release negatively charged hydroxide ions, OH-, in the water.

• NaOH +H2O ---------> Na+ + OH- + H2O

Strengths of Acids and Bases

• The strength of an acid depends on how easily the acid will release H+ (hydrogen) ions when in water

• The strength of a base depends on how easily the base will release OH- (hydroxide) ions when in water

Indicators

• Indicators are compounds that react with acidic and basic solutions and produce certain colors, depending on the solution’s pH.

• Indicators help you determine the pH of a solution.

*Litmus paper is an indicator

It shows if a substance is an acid or a base:Red litmus paper in a base solution turns blueBlue litmus paper in an acid turns red

*Universal Indicator33

Gives you more information than the Litmus paper because gives you the pH value of the substance

pH and pH Scale

pH is a measure of how acidic or basic a solution is and depends on the concentration of hydronium and hydroxide ions.“pH stands for percentage hydrogen”

pH and pH Scale

• The pH scale ranges from 0 to 14.

• Acidic solutions have pH values below 7.

• A solution with a pH of 0 is very acidic.

• A solution with a pH of 7 is neutral.

• Basic solutions have pH values above 7.

Mini Lab 1:Litmus paper

• In groups.

• Each group has 2 substances ( vinegar and ammonia), 2 strips of red litmus paper and 2 strips of blue litmus paper.

• Dip one red strip and one blue inside each one of the substances and record your results on a table.

Mini Lab 1:

Litmus paper Ammonia Soda

Red color ? color ?

Blue color ? color ?

Acid or Base? ? ?

Mini Lab:

• Write a paragraph explaining why you obtained such results and if the substances you tested are acids or bases .

• Explain what is the role of the paper you used during the experiment and why did it changed color.

Mini Lab 1:

Litmus paper Ammonia Soda

Red Turn blue Stay red

Blue Stay blue Turn red

Acid or Base? base acid

*Properties of Acidic Solutions

-sour taste-can conduct electricity because it has ions-are corrosive, which means they break down -certain substances. Many acids can corrode fabric, skin, and paper.

-react strongly with certain metals.

Uses of Acids

Acetic Acid - vinegar and salad dressings

Citric Acid in limes, lemons and oranges

Ascorbic acid – vit C

Sulfuric acid - fertilizers, steel, paints, and plastics.Acids – batteries

Properties of Basic Solutions

Slippery

Bitter taste

Bases are corrosive.

can conduct electricity ( have ions)

Basic solutions are not as reactive with metals as acidic solutions are.

Uses of Bases

• soaps, ammonia, and many other cleaning products

• Chalk is basic

• Blood is basic

Neutralization

*Neutralization is the chemical reaction of an acid with a base. Ex:

It is a chemical reaction because new substances are being formed ( salt and water)

*How does neutralization occur?

Recall that every water molecule contains two hydrogen atoms and one oxygen atom.

The reaction of a base and an acid results in water and a salt . Water has a neutral pH.It is called neutralization because the acid and thebase are not there anymore…….

HCl + NaOH NaCl + H20 ( neutral)

Lab:

• Creating a pH scale