*NAME- PIYUSH BHANDARI

*CLASS- ‘10’th

*SECTION- ‘A’*

*SUBJECT- SCIENCE P.P.T

*SUBMITTED TO- RAHUL GAUR

Chapter -2

Acids

An acid is a substance that produces hydrogen ions (H+) when placed in waterWhen acids/ ionic compounds are dissolved in water,

the ions split apart from each other (dissociation)

Photo courtesy of:http://www.biologycorner.com/worksheets/acids_bases_coloring.html

Properties of Acids

Most acids…Taste sourReact w/many metals to form H2 gas

Are corrosive (appears to “eat away” materials while reacting)Have a chemical formula that begins with H

Photo Courtesy of:http://healthmad.com/conditions-and-diseases/the-surprising-health-benefits-of-lemons/

Zinc Metal + Hydrochloric Acid ??

Zn (s) + 2 HCl (aq)

Predict the type of reaction based on the reactants!

Single-Displacement

Predict the products of this reaction.

H2 (g) + ZnCl2 (aq)

Common Acids• Citric Acid

Found in citrus fruits• Used as a preservative

• Lactic Acid Found in yogurt Produced by our muscles when they are overworked

• Acetic Acid (HC2H3O2) Vinegar Used as a preservative

• Carbonic Acid ( H2CO3) or Phosphoric Acid (H3PO4) Found in soft drinks

• Hydrochloric Acid (HCl) Found in our stomachs- aids in food digestion

Photo Courtesy of:http://stayinhealth.wordpress.com/2010/02/08/sugary-soft-drinks-increase-pancreas-cancer-risk

Bases

A base is a substance that produces hydroxide ions (OH-) when placed in water○ When bases/ ionic compounds are

dissolved in water, the ions split apart from each other (dissociation)

Photo courtesy of:http://www.biologycorner.com/worksheets/acids_bases_coloring.html

Properties of Bases

Most bases…Taste bitterFeel slipperyAre corrosive (appears to “eat away” materials while reacting)Have a chemical formula that ends with OH

Photo Courtesy Of:http://www.pbs.org/wgbh/nova/body/bitter-taste.html

Common Bases

o Ammonia• Cleaners and fertilizers

Sodium hydroxide• Used in soaps and drain cleaners

Magnesium hydroxide• An ingredient found in antacids

Indicators Indicators are used to determine if a substance is

an acid or a base An indicator changes a specific color when in the

presence of an acid or a base Litmus Paper: indicator made of a special filter paper

that contains dyes extracted from lichens (the crusty “stuff” that grows in rocks) Blue litmus turns red in an ACID

Red litmus turns blue in a BASE Why do you think it’s important to test an

unknown substance with both types of litmus paper?

If one type of litmus paper does not change color, that does not guarantee that the other type of litmus paper will change color (i.e. water)

pH

The pH scale can also help us classify solutions as acids or bases

pH is a measure of the amount of H+ ions in a solution (potential hydrogen)

The more H+ ions, the lower the pH, the more acidic the solution

pH Scale

7 < pH ≤ 14

Complete the following chart by telling whether the pH represents an acid, base or neutral substance.

Also tell what color each type of litmus paper will turn at that pH level.

pH Acid/Base/Neutral Color of Blue Litmus Paper Color of Red Litmus Paper

2      

8      

4      

7      

13      

Strength vs Concentration When describing acids and bases, strength and

concentration do not mean the same thing!

Strength refers to the ability of the acid/base to dissociate in solution ○ pH measures this• Dissociation refers to the ability of an ionic compound to

break apart into ions

Concentration refers to the amount of acid/base dissolved in solution. ○ An acid or base will have the same pH, regardless of how

concentrated it is• Just because you add water to dilute it, it’s still going to have the

same amount of H+ ions, they’ll just be spread out more

Strong/Weak Acids & Bases

When a strong acid/base dissolves in water, nearly all of the acid/base molecules will dissociate into ions The greater the ability to dissociate, the

more potential the acid or base has for being dangerous because there are more ions available to react

When a weak acid/base dissolves in water, only a small fraction of the acid/base molecules dissociate (dissociate partially) With less ions in solution, there is less

potential for danger because there are less ions available to react

Hydrogen

Hydrogen

Strong/Weak Acids Examples Strong Acids 1. HCl – hydrochloric acid – stomach

acid

2. H2SO4 – sulfuric acid – battery acid

3. HNO3 – nitric acid

Weak Acids:

1. HC2H3O2 – acetic acid – vinegar

2. H3C6H5O7 –citric acid –citrus fruits

Strong/Weak Bases Examples

Strong Bases: 1. NaOH – sodium hydroxide 2. Any alkali or alkaline earth metal with OH-

(i.e. KOH – potassium hydroxide) Weak Bases: 1. Al(OH)3 – aluminum hydroxide – often found in

deodorants 2. NH4OH – ammonium hydroxide (ammonia) –used in

many cleaning products

Neutralization Neutralization is a chemical reaction between an

acid and a base that takes place in a water solution

When acids and bases react, the H+ ions from the acid react with the OH- ions from the base to form HOH (H2O - water!)

The overall pH becomes “neutral”

Many people that suffer from heartburn will take antacids to ease their symptoms (i.e TUMS). How do you think antacids work?

The stomach is acidic due to HCl and antacids are basic. A neutralization reaction occurs!

Salts The ions that are left behind after the H+ and OH-

ions form water, combine to form a saltA salt is a compound that forms when the negative ions

from the acid combine with the positive ions from the base

Acid + Base Water + Salt

HCl(aq) + KOH(aq) H2O(l) + KCl(aq)

What type of reaction is a neutralization reaction?Double-Displacement

Name the salt produced in this neutralization reaction.Potassium chloride