lesson 7 acids and bases
TRANSCRIPT
Lesson 7
Acids and Bases
Identifying Acids and Bases
Objectives define acids and bases; and 1
At the end of the lesson, you should be able to:
recognize the general properties of acids and bases.
2
Learn about It!
Acids and bases are compounds made up of two or moreelements.
Acids Bases
sour taste bitter taste
hot and corrosive slippery texture
irritating smell irritating smell
conductors of electricity conductors of electricity
reacts with metals to produce hydrogen gas
reacts with fats to form soap
Learn about It!
● It contains water soluble dyes from lichens absorbed in a filter paper.
● It has two types: the red litmus paper and the blue litmus paper.− An acid turns the blue litmus paper to red.− A base turns the red litmus paper to blue.
Litmus Paper Test
blue and red litmus paper
Learn about It!
● When an acid reacts with a base, water and salt is formed. The reaction is called neutralization.
acid + base → salt + water
Neutralization
Learn about It!
● These are compounds that could act as both an acid or a base.
● One example is sodium bicarbonate (NaHCO3).
Amphoteric Compounds
baking soda (sodium bicarbonate)
Learn about It!
Arrhenius Acid● It is a substance that
dissociates in water to form hydrogen ions (H+).
● It increases the concentration of hydronium ion in an aqueous solution.
Arrhenius Theory
When an acid dissociates in water, it forms hydrogen ions.
Learn about It!
Arrhenius Base● It is a substance that
dissociates in water to form hydroxide ions (OH-).
● It increases the concentration of hydroxide ion in an aqueous solution.
Arrhenius Theory
When a base dissociates in water, it forms hydroxide ions.
Learn about It!
Some household examples of Arrhenius acids and Arrhenius bases.
Try it!
Identify the following if it is acidic or basic.1. soft drinks2. vinegar3. liquid sosa4. muriatic acid5. potassium hydroxide solution
Try it! Solution
Identify the following if it is acidic or basic.1. soft drinks
acidic2. vinegar
acidic3. liquid sosa
basic4. muriatic acid
acidic5. potassium hydroxide solution basic
Key Points
Acids and bases are made up of two or more elements combined chemically.● Acids have a sour taste, irritating smell, and hot and
corrosive. It is also a good conductor of electricity. It reacts with metals to produce hydrogen gas.
● Bases have a bitter taste, pungent smell, and slipper texture. It is also a good conductor of electricity. It reacts with fats to form soap
1
When an acid reacts with a base, water and salt is formed. The reaction is called neutralization.2
Key Points
A litmus paper test is a rapid and the most common test used to determine if a given solution is acidic or basic.● An acid turns the color of blue litmus paper to red.● A base turns the color of red litmus paper to blue.
3
Compounds that could act as an acid or a base are called amphoteric compounds.4
Key Points
The Arrhenius Theory by Svante Arrhenius explains the concept of acids and bases based on the dissociation in water.● An Arrhenius acid is a substance that dissociates in
water to form hydrogen ions (H+).● An Arrhenius base is a substance that dissociates in
water to form hydroxide ions (OH-).
5
Check Your Understanding
Identify if the following compound as an acid or a base.
1. tea2. orange juice3. bitter gourd4. acetic acid5. milk of magnesia (or magnesium hydroxide)
Challenge Yourself
What are the limitations of the Arrhenius theory? Can you classify ammonia as an Arrhenius acid or an Arrhenius base?
Lesson 4.2
Strengths of Acids and Bases
Objectivesdifferentiate strong and weak acids and bases; and
use different tools and techniques to classify acids and bases based on their strengths.
1
At the end of the lesson, you should be able to:
2
Learn about It!
● A strong acid completely dissociate in water to yield hydrogen (H+) ions. − There are only 7 strong acids: hydrochloric acid,
hydrobromic acid, hydroiodic acid, nitric acid, chloric acid, perchloric acid, and sulfuric acid (for the first dissociation of hydrogen ion only).
● A weak acid does not dissociate completely in water. The amount of dissociation for weak acids is usually less than 1%
Strong and Weak Acids
Learn about It!
● A strong base completely dissociates in water to yield hydroxide (OH-) ions.− Hydroxides of alkali metals (Group 1 elements) and alkaline
earth metals (Group 2 elements) are strong bases. Some strong bases are: sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide.
● A weak base does not dissociate completely in water. The amount of dissociation for weak bases is usually less than 1%.
Strong and Weak Bases
Learn about It!
Strong and Weak Acids and Bases
Examples of acids. Examples of bases.
Learn about It!
● It is a simple numerical way of describing the acidity of a solution.
● It was proposed by Danish chemist Soren Peder Lauritz Sorensen.
● Values of pH ranges from 1 to 14. Each region of the pH scale maybe used to identify an acidic, basic, or neutral solution.
The pH scale
Learn about It!
● pH values between 1 to 7 are acidic.
● pH value of 7 means that the solution is neutral.
● pH values between 7 to 14 are basic.
The pH scale
The pH scale.
Learn about It!
The pH values of certain commons chemicals at home is shown.
Examples
pH values of common household products.
Learn about It!
● These are substances that change into a specific color for certain pH ranges, usually one range for acids and another for bases.
● There are two types: natural indicators and pH indicators
Acid-Base Indicators
Learn about It!
Plants that are used as acid-base indicators are called natural indicators.
Natural Indicators
Colors of solutions at different pH levels using red cabbage as indicator
Common natural indicators and their color for acids and bases.
Learn about It!
● These are readily available indicators that could be used for specific pH ranges.
● The active compound in pH indicators also shows a specific color for acidic and basic solutions.
pH Indicators
Colors of solutions at different pH levels using phenolphthalein as indicator.
Common pH indicators and their color for acids and bases.
Learn about It!
pH paper● It is the improved version of the
litmus paper.● It contains a mixture of pH indicators
called the universal indicator that can determine the specific pH range of the solution.
● The color is matched to the given color chart.
Measurement of pH
pH paper
Learn about It!
pH meter● It is used to quantitatively determine
the exact pH of the solution.
Measurement of pH
pH meter
Try it!
Fill up the table below.
Solution Acid or Base? Strength pH value
hydrochloric acid
salt water
sodium hydroxide
acetic acid
copper hydroxide
Try it! Solution
Fill up the table below.
Solution Acid or Base? Strength pH value
hydrochloric acid acid strong pH < 7
salt water neither NA pH = 7
sodium hydroxide base strong pH > 7
acetic acid acid weak pH < 7
copper hydroxide base weak pH > 7
Key Points
A strong acid completely dissociates in water to yield hydrogen (H+) ions. A weak acid does not dissociate completely in water.
1
The pH scale is a simple numerical way of describing the acidity of a solution.● pH values between 0 to 7 are acidic.● pH value of 7 means that the solution is neutral.● pH values between 7 to 14 are basic.
3
A strong base completely dissociates in water to yield hydroxide (OH-) ions. A weak base does not dissociate completely in water.
2
Key Points
An acid-base indicator is a substance that changes into a specific color for certain pH ranges, usually one range for acids and another for bases.● Plants that are used as acid-base indicators are called
natural indicators.● pH indicators are readily available indicators that
could be used for specific pH ranges.
4
pH paper is used to determine the approximate pH value of a certain solution from pH 1 to 14. It contains a mixture of pH indicators called the universal indicator.
5
Key Points
The pH meter is used to quantitatively determine the exact pH of the solution.6
Check Your Understanding
Classify the following either as a strong acid, weak acid, strong base, or weak base.
1. hydrofluoric acid2. ammonia3. sulfuric acid4. barium hydroxide5. aluminum hydroxide
Challenge Yourself
Can you use other violet-colored plants such as the duhat fruit as acid-base indicators?
duhat
Lesson 4.3
Safety Precautions in Handling Acids and Bases
ObjectiveAt the end of the lesson, you should be able to:
enumerate proper safety protocols in handling acids and bases.
1
Learn about It!
● You should always wear personal protective equipment when in the laboratory.
● This includes a lab coat, eye goggles, comfortable clothing, closed shoes, long pants, and gloves.
Personal Protective Equipment
personal protective equipment
Learn about It!
● It is best to check the MSDS to look for information about the substances that you will handle when working with chemicals.
● It is important to know the general hazards involved with the chemicals you are about to handle.
Material Safety Data Sheet (MSDS)
An example of a Material Safety Data Sheet (MSDS).
Learn about It!
● Acids and bases are irritants.● Concentrated acids and bases can easily damage tissue.● Contact can cause severe damage to skin and eyes.● Concentrated gases can also damage skin, eyes, and lungs.● Inhaling dry powder can cause severe respiratory damage.
General Health Effects
Learn about It!
● Work with small amounts.● Do not mix acids and bases unless it is what is required in
your experiment.● Never add water to acids.
Working with Acids and Bases
Learn about It!
● Spills should be neutralized immediately and cleaned up using a paper towel or a sponge.
● For cases of spills on the skin, do not neutralize. Wash well with running water.
In Case of Spills
Learn about It!
● Every laboratory must have protocols on how to dispose of chemical wastes.
● Some low concentration acids and bases may be dilute and flushed down the sink.
● Most chemical wastes must be collected on a chemical waste jar and disposed of according to the laboratory standard operating procedures.
Waste Procedures
Try it!
1. Lab coats provide general protection for your clothing and skin.
2. Dilute acidic solutions by adding water into them in a volumetric flask.
3. Slippers can be worn inside the laboratory.4. If you wear eyeglasses already, there is no need for you to
wear goggles in the lab.5. For cases of spills of acid on the skin, wash it with a base.
Write T if the statement is true. Otherwise, write F.
Try it! Solution
Write T if the statement is true. Otherwise, write F.1. Lab coats provide general protection for your clothing and
skin. T2. Dilute acidic solutions by adding water into them in a
volumetric flask. F3. Slippers can be worn inside the laboratory. F4. If you wear eyeglasses already, there is no need for you to
wear goggles in the lab. F5. For cases of spills of acid on the skin, do not wash it with a
base. T
Key Points
Always wear personal protective equipment when in the laboratory. This includes a lab coat, eye goggles, comfortable clothing, closed shoes, long pants, and gloves.
1
When working with chemicals, it is best to check the material safety data sheet (MSDS). 2
Generally, acids and bases are irritants.3
Key Points
Spills should be neutralized immediately and cleaned up using a paper towel or a sponge. For cases of spills on skin, do not neutralize. Wash well with running water.
5
Work with small amounts of acids and bases. Never add water to acids.4
Dispose chemical wastes properly.6
Check Your Understanding
Read the excerpt below. Indicate everything that is wrong in this excerpt. Charlene is running late for her Chemistry laboratory class. The strap of herslippers almost tore apart as she rushed to her classroom. She put on her labcoat and immediately goes through her class experiment. She adds water tothe flask with acid to dilute the acid into half its concentration. She directlysmells one of the flasks to find out which one is the base. To make sure, sheuses a spatula to scoop some of the acid to her hand so she could feel if it isindeed slippery. She adds the acid and the base as indicated in her labmanual. The swirls the flask vigorously. She didn’t notice the heat from theflask until the flask breaks and she spills the contents onto the table. Sheimmediately runs to her teacher to tell her what happened. She then struts tothe comfort room to wash her hands that got wet with the spill.
Challenge Yourself
Why should water be never added to concentrated acids?
Bibliography
Mendoza, E. 2003. Chemistry. Quezon City: Phoenix Publishing House, Inc.
Padolina, M.C.D., Simon-Antero, E. and Alumaga, M.J.B. 2010. Conceptual and Functional Chemistry (2nd
ed.). Quezon City: Vibal Publishing House, Inc.
Religioso, T.F. and Vengco, L.G. 2011. You and the Natural World Integrated Science (3rd ed.). Quezon City: Phoenix Publishing House, Inc.
Northwestern University. “Laboratory Safety.” Accessed April 9, 2017. http://faculty.washington.edu/korshin/Class-486/AEESP-safety-notes.pdf
Purdue University. “The Lewis definitions of acids and bases.” Accessed April 8, 2017. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch11/lewis.php
Wisconsin University. “ChemPages Netorials – Acids and Bases Module.:”Accessed April 7, 2017. https://www.chem.wisc.edu/deptfiles/genchem/netorial/rottosen/tutorial/modules/acid_base/index.htm
Bibliography
Mendoza, E. 2003. Chemistry. Quezon City: Phoenix Publishing House, Inc.
Padolina, M.C.D., Simon-Antero, E. and Alumaga, M.J.B. 2010. Conceptual and Functional Chemistry (2nd
ed.). Quezon City: Vibal Publishing House, Inc.
Religioso, T.F. and Vengco, L.G. 2011. You and the Natural World Integrated Science (3rd ed.). Quezon City: Phoenix Publishing House, Inc.
Purdue University. “The Lewis definitions of acids and bases.” Accessed April 8, 2017. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch11/lewis.php
Wisconsin University. “ChemPages Netorials – Acids and Bases Module.:”Accessed April 7, 2017. https://www.chem.wisc.edu/deptfiles/genchem/netorial/rottosen/tutorial/modules/acid_base/index.htm
Bibliography
Mendoza, E. 2003. Chemistry. Quezon City: Phoenix Publishing House, Inc.
Padolina, M.C.D., Simon-Antero, E. and Alumaga, M.J.B. 2010. Conceptual and Functional Chemistry (2nd
ed.). Quezon City: Vibal Publishing House, Inc.
Religioso, T.F. and Vengco, L.G. 2011. You and the Natural World Integrated Science (3rd ed.). Quezon City: Phoenix Publishing House, Inc.
Purdue University. “The Lewis definitions of acids and bases.” Accessed April 8, 2017. http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch11/lewis.php
Wisconsin University. “ChemPages Netorials – Acids and Bases Module.:”Accessed April 7, 2017. https://www.chem.wisc.edu/deptfiles/genchem/netorial/rottosen/tutorial/modules/acid_base/index.htm
Photo Credits
● Slide 6: This file, Blue and Red litmus papers, by Kanesskong is licensed under CC BY-SA 4.0 via Wikimedia Commons.
● Slide 13: This file, pH meter togopic, by Database Center for Life Science (DBCLS), is licensed underCC BY 3.0 via Wikimedia Commons.
● Slide 20: This file, Jamuk, by েমৗচ�মী, is licensed under CC BY-SA 3.0 via Wikimedia Commons.