. An acid is a substance that produces hydrogen ions (H + ) when placed in water o When acids/...
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Transcript of . An acid is a substance that produces hydrogen ions (H + ) when placed in water o When acids/...
An acid is a substance that produces hydrogen ions (H+) when placed in watero When 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
Most acids…oTaste souroReact w/many metals to form H2 gasoAre corrosive (appears to “eat away” materials while reacting)oHave 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)
• Citric Acid o Found in citrus fruits• Used as a preservative
• Lactic Acid o Found in yogurto Produced by our muscles when they are overworked
• Acetic Acid (HC2H3O2)o Vinegaro Used as a preservative
• Carbonic Acid ( H2CO3) or Phosphoric Acid (H3PO4)o Found in soft drinks
• Hydrochloric Acid (HCl)o 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
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
Most bases…oTaste bitteroFeel slipperyoAre corrosive (appears to “eat away” materials while reacting)oHave a chemical formula that ends with OH
Photo Courtesy Of:http://www.pbs.org/wgbh/nova/body/bitter-taste.html
o Ammonia• Cleaners and fertilizers
o Sodium hydroxide• Used in soaps and drain cleaners
o Magnesium hydroxide• An ingredient found in antacids
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)
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)
o The more H+ ions, the lower the pH, the more acidic the solution
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
When describing acids and bases, strength and concentration do not mean the same thing!
o 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
o 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
When a strong acid/base dissolves in water, nearly all of the acid/base molecules will dissociate into ionso 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)o With less ions in solution, there is less
potential for danger because there are less ions available to react
Hydrogen
Hydrogen
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 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 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!
The ions that are left behind after the H+ and OH- ions form water, combine to form a salto A 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
Acid/Base/Salt Color of Blue Litmus Paper Color of Red Litmus Paper
NaOH
HCl
Ba(OH)2
Al(NO3)3
H2SO4
Classify each of the following compounds as an acid, base or salt.
Then indicate what color each type of litmus paper will turn when placed in this substance.