leq: what techniques in the lab setting will be used to identify acids and bases?

Physical Science Chapter 23

Acids and BasesLEQ: What techniques in the lab setting will

be used to identify acids and bases?

LEQ: What techniques in the lab setting will be used to identify acids and bases?

Acids Bases

Produce H+ ions in water

Form hydronium ions (H30+)

Taste sourProduce hydrogen

gas when react with metals

Change litmus paper red

Produce OH- (hydroxide) ions in water

Feel slipperyTaste bitter, chalkyChange litmus

paper blue


How are they alike?CorrosiveReact with indicators and change colorConduct electricity (electrolytes)React with each other to form salt and

water


Common Acids

þ Soda

þ Coffee

þ Wine

þ Grapefruit (citric acid)

þ Yogurt (lactic acid)

þ Pickled foods in vinegar (acetic acid or CH₃COOH)

þ Fertilizers (sulfuric, nitric, phosphoric, HCL)

þ Car batteries (sulfuric acid or H₂SO₄)

LEQ: What techniques in the lab setting will be used to identify acids and bases?Common bases

Egg whites

Baking powder

Milk of magnesia

Mg(OH)2

Antacids – Al(OH)3

Soap - NaOH

Shampoo

Ammonia - NH3

Oven cleaner -

NaOH

Drain cleaner -

NaOH

Fertilizers – NH3


What does it mean to dissociate?To break apartProcess in which an ionic compound separates into its positive and negative ions


How do acids dissociate in water and what products are formed?

The negative areas of nearby6 water molecules attract the positive hydrogen in the acid.

Produces a hydronium ion and an anion


How do bases dissociate in water and what products are formed?

The negative areas of nearby water molecule attract the positive ion in the base. The positive area of the water molecule attract the hydroxide ion.

Water molecules do not combine with the ions formed from the base.

Produces a positive ion, a hydroxide ion, and water


Explain how ammonia (NH3) is considered a base when it does not contain OH-.

The ammonia attracts a hydrogen from the water forming ammonium ion and a hydroxide ion.


Identify each as characteristic of an A) acid or B) base

____ 1. Sour taste

____ 2. Produces OH- in aqueous solutions

____ 3. Chalky taste____ 4. Is an electrolyte____ 5. Produces H+ in aqueous solutions


Describe the solution in each of the following as: 1) acid 2) base or 3)neutral.A. ___soda

B. ___soapC. ___coffeeD. ___ wineE. ___ water

F. ___ grapefruit


Identify each as a characteristic of an A) acid or B) base

_A_ 1. Sour taste

_B_ 2. Produces OH- in aqueous solutions

_B_ 3. Chalky taste

A, B 4. Is an electrolyte

_A_ 5. Produces H+ in aqueous solutions


Describe each solution as: 1) acid 2) base or 3) neutral.A. _1_ soda

B. _2_ soapC. _1_ coffeeD. _1_ wineE. _3_ water

F. _1_ grapefruit


Strong acids Weak acids

Nearly all acids molecules dissociate into ions

Strong electric currentSingle arrow in

chemical equationHCl + H2O H3O+ +

Cl-

Example: HCl, HNO3, H2SO4

Partially dissociate into ions in water

Weak electric currentDouble arrow in

chemical equationCH3COOH + H2O

H3O+ + CH3COO-

Examples: acetic acid, carbonic acid


Differentiate between strong and weak bases.

Strong completely dissociates and weak partially dissociates.

NaOH Na + + OH-

NH3 + H2O NH4+ + OH-


Differentiate between strength and concentration.Strength

Strong or weakHow easily acids and bases dissociate in water

ConcentrationConcentrated – a large amount of acid or base in a

given amount of waterDiluted – a little acid or base in a large amount of water

Amount of acid or base dissolve


pH scale - measures how acidic or basic a solution is based on concentration of H+ions

Ways to test pHpH paperpH meter****litmus paper just tells if it is an acid or

base****Buffers – used to minimize the effects of acids

or bases on pH

pH lower than 7: acidic (high H+ concentration)

pH higher than 7: basic (low H+ concentration)

pH at 7: neutral


NeutralizationA chemical reaction between an acid and a

base that takes place in a water solutionH+ + OH- H2O

Cl- + Na+ NaClTherefore,

acid + base salt + waterHCl + NaOH H2O + NaCl


What is titration?When a solution of known concentration and

volume is used to determine the concentration of another solution


What are the steps of titration?Place a known volume of acid that has an unknown

concentration in a beakerAdd a few drops of phenolphthalein (indicator) to

beaker (colorless in acid but turns bright pink in base)

Slowly add base solution of known concentration (standard solution) to acid and indicator solution using the burette system

Continue to add base drop by drop until solution turns pink and the color persist (end solution/neutralization)

LEQ: What are some causes and effects of acid rain?

Causes:Burning of fossil fuels

Effects:Corrode or eat away at substancesDestroy plant and animal life

Solutions:Reduce pollutionAdd lime to acidic water

Differentiate between acids and basesAcids produce hydrogen ions which

attach to the water molecule forming a hydronium ion. They turn litmus paper red, are low on the pH scale and taste sour.

Bases produce hydroxide ions in solution. They turn litmus paper blue, have a high pH, and taste bitter or chalky.

How are acids and bases alike?Both acids and bases are corrosive

to metals and can burn tissue. They change colors in the presence of indicators. They both produce electrolytes meaning that they have the ability to conduct electricity. When they react with each other to form salt and water.

What is an example of an indicator?Litmus paperphenolphthalein

Explain the process of dissociation of bases and be specific on what products are produced.When a base is added to water, the

water molecule dissociates the base forming a cation and a hydroxide ion. The water molecule remains as a water molecule.

Explain the process of dissociation of acids and be specific on what products are produced.When an acid is added to water, the

negative side of the water molecule removes the hydrogen from the acid forming a hydronium ion and leaving an anion.

Explain in detail how ammonia dissociates in water. Explain how this proves that ammonia is a base.Ammonia does not have a hydroxide ion

as part of its formula. When ammonia is added to water, it removes a hydrogen ion from the water molecule leaving behind a hydroxide ion. The removed hydrogen attaches to the ammonia creating the ammonium ion. Due to the hydroxide ion being produced, this proves that ammonia is a base.

Differentiate between strong acids/bases and weak acids/bases.Strong acids and bases dissociate completely in

water. Strong acids have low pH numbers and strong bases have high pH numbers. Both of their equations contain a single arrow pointing toward the product side. Strong acids and bases both have the ability to produce a strong electric current.

Weak acids and bases partially dissociate in water. Their pH numbers are closer toward the middle of the pH scale with the exception to 7 (seven) which is neutral. Their equations contain a double arrow. Weak acids and bases only produce a small electric current.

Differentiate between strength and concentration.Strength refers to the ease at which acids

and bases dissociate in water. If they dissociate completely; then, they are strong. If they only partially dissociate; then, they are weak.

Concentration refers to the amount of acid or base present in a solution. The solution is considered concentrated if there is large amount of acid or base and little water. The solution is considered diluted if there is minimal amounts of acid or base in a large amount of water.

What is the purpose of buffers?Buffers are used to minimize the effects of

acids or bases on pH within the body so that the pH level of the body stays close to neutral.

leq: what techniques in the lab setting will be used to identify acids and bases?

Documents