QOTD 5/14/14 Please 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 M HCl (strong acid) 100% ions (excess H+) 0.5 M HCl (strong acid) 100% ions (excess H+) 1 M vinegar (weak acid) less than 100% ions (~1%) Pure water neutral 1 M NH3 (weak base) less basic than a strong base 1 M NaOH (strong base) strong base = most basic = least acidic

Answers Homework Qs! (p. 59)

The 1.0 M HCl because it dissociates completely…more H+ means lower pH 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, HI b. Rubidium Hydroxide, RbOH c. 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-

10 Br- ions (to cancel out the 10 H+ ions) 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)

PLEASE SEND A GROUP MEMBER TO GRAB NOTES SHEETS! 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 + Base Acid Proton acceptor Proton donor

BAAD Bases Accept, Acids Donate Example: HCl + H2O  Cl- + H3O+ NH3 + H2O  NH4+ + OH- Acid Base H+ Acid Base 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? HBr H2O

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 7 14 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 7 14 Increasing strength Increasing strength Acids Neutral (water) Bases

pH Scale Acidic Neutral solution Basic http://staff.jccc.net/pdecell/chemistry/phscale.html

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)