QOTD 5/14/14Please have out to be checked off:• Soap reading/prelab Qs• p. 59 Qs

QOTD: Rank the following solutions in order of most acidic to least acidic and explain why.• 1 M vinegar (weak acid)• 1 M HCl (strong acid) • 0.5 M HCl (strong acid)• 1 M NaOH (strong base)• 1 M NH3 (weak base)• Pure water

QOTD Answer

QOTD: Rank the following solutions in order of most acidic to least acidic and explain why.1. 1 M HCl (strong acid) 100% ions (excess H+)2. 0.5 M HCl (strong acid) 100% ions (excess H+)3. 1 M vinegar (weak acid) less than 100% ions (~1%)4. Pure water neutral5. 1 M NH3 (weak base) less basic than a strong base

6. 1 M NaOH (strong base) strong base = most basic

= least acidic

Answers Homework Qs! (p. 59)

Check-in Questions: 1. You have a 1.0 M solution of a strong acid (HCl) and 1.0 M of a weak acid (acetic acid). Predict which will have a lower pH, and explain why:

The 1.0 M HCl because it dissociates completely…more H+ means lower pH

Check-in Questions: 2. How is the Bronsted-Lowry definition of acid/base theory different from Arrhenius?

The Bronsted-Lowry theory says that a base can accept a proton (H+) (in addition to donating a OH-).

Homework Questions:1. Label the following substances as acids or bases. In each case, list the ions you would expect to form in solution: a. Hydroiodic Acid, HIb. Rubidium Hydroxide, RbOHc. Selenous acid, H2SeO4

d. Phosphine, PH3

e. Calcium hydroxide, Ca(OH)2

f. Perchloric acid, HClO4

Acid, H+, I-

Base, Rb+, OH-

Acid, 2 H+, SeO42-

Base, PH4+, OH-

Base, Ca2+, 2 OH-

Acid, H+, ClO4-

2. Consider a solution of hydrobromic acid, HBr. If you drew a particle view of HBr in water that contained 10 H+ ions, how many Br- ions would you need? Explain your thinking:

10 Br- ions (to cancel out the 10 H+ ions)3. Consider a solution of mangnesium hydroxide, Mg(OH)2. If you drew a particle view of this substance with 10 Mg2+ ions, how many hydroxide (OH- ) ions would you need to draw?

20 OH- ions

4. The CO32- ion is a weak base. Explain, using Bronsted-Lowry theory, what makes this

substance a base:

It can accept a proton (H+)

Challenge: Some solutions conduct electricity better than other solutions. Use your knowledge about the different kinds of acids and bases to explain why a 1.0 M hydrochloric acid solution is a better conductor of electricity than a 1.0 M acetic acid solution.

The strong acid dissociates completely, making it easier for electricity to flow through the solution . (more ions = more moving charges)

Acids and Bases Notes

PLEASE SEND A GROUP MEMBER TO GRAB NOTES SHEETS!

Arrhenius Theory

• Acid: A substance that adds hydrogen ions, H+, to an aqueous solution

• Base: A substance that adds hydroxide ions, OH-, to an aqueous solution

• Not the best definition…

Bronsted-Lowry Definition

• Acid: Any chemical that donates a hydrogen ion, H+

• Base: Any chemical that accepts a hydrogen ion into their structure

Acid Base

+

Proton donor

Proton acceptor

BAAD

• Bases Accept, Acids Donate

Example:

HCl + H2O Cl- + H3O+

NH3 + H2O NH4+ + OH-

H+

Acid Base

AcidBase

H+

Other terms to know

• Hydronium ion: H3O+

• Hydroxide ion: OH-

• Amphoteric (or amphiprotic) : Water can act as both an acid and a base in different situations

Your Turn (partner talk)

H2O + HBr Br- + H3O+

Which compound is acting as an acid?Which is acting like a base?

HBrH2O

Your Turn (Partner talk)

H2O + SO42- OH- + HSO4

-

Which of the compounds is acting as a base?

SO42-

Your Turn (partner talk)

• Predict the products when phosphoric acid (H3PO4) is added to water:

H3PO4 + H2O H2PO4- + H3O+

Properties of Acids

• Corrosive• Sour taste • Contains hydrogen ions (H+) when dissolved in

water • pH < 7• Electrolytes (conduct electricity)• Neutralize bases

http://qldscienceteachers.tripod.com/junior/chem/acid.html

Examples of Acids

• Hydrochloric acid (HCl) in gastric juice • Sulphuric acid (H2SO4) • Nitric acid (HNO3) • Carbonic acid in soft drinks (H2CO3) • Uric acid in urine • Ascorbic acid (Vitamin C) in fruit • Citric acid in oranges and lemons • Acetic acid in vinegar

http://qldscienceteachers.tripod.com/junior/chem/acid.html

Properties of Bases

• Taste bitter

• Slippery

• Electrolytes (conduct electricity)

• Base + fat = soap

• Neutralize acids

• Corrosive

http://qldscienceteachers.tripod.com/junior/chem/acid.html

Examples of Bases

• Sodium hydroxide (NaOH) • Calcium hydroxide ( Ca(OH)2 ) or limewater • Ammonium hydroxide (NH4OH) or ammonia

water • Magnesium hydroxide ( Mg(OH)2 ) or milk of

magnesia • Many bleaches, soaps, toothpastes and

cleaning agents

http://qldscienceteachers.tripod.com/junior/chem/acid.html

Indicators

• Substances that change color when exposed to an acid or base

• Can be used to identify acids and bases, even their strength

• Usually a weak acid or base

Examples of indicators

• Litmus paper: Red for acid, blue for base• pH paper: universal indicator, compare colors

to known pH• Cabbage juice: color changes in response to

concentration of H+ ions• Phenolphthalein: color is clear/cloudy in an

acid and pink in a base

Solutions• Acidic solution: the hydronium ion

concentration is higher than the hydroxide ion concentration [H+] > [OH-]

• Basic solution: hydroxide ion concentration is higher than the hydronium ion concentration

[H+] < [OH-]

• Neutral solution: concentration of hydronium and hydroxide ions is the same

[H+] = [OH-]

– Ex. Pure water– Created when equal quantities of an acid and

base are combined

pH

• pH: Measures the concentration of H3O+ ions

• pH scale: A numeric scale used to describe the acidity of a solution from 0 to 14

• Draw the scale below

0 7 14Acids Neutral

(water)

BasesIncreasing strength Increasing strength

pH Scale

http://staff.jccc.net/pdecell/chemistry/phscale.html

Neutral solution

Acidic

Basic

Strong vs. Weak Acids and Bases

• Strong Acid or Base: all of the molecules dissociate (split apart) into ions

• Weak Acid or Base: Only some of the molecules actually dissociate– Not as many H+ or OH- ions in solution

Strong base

Weak base

Soap!• Let’s review the soap procedure…

• SAFETY! What will you use to protect yourself?GOGGLES FOR EVERYONE!Gloves for the person who pours the NaOH and mixes it.

• How hot will you make the NaOH and Oils?50 degrees! They both need to be around 50 (+ or – a couple degrees)