Chapter 7

Acids & Bases

About Acids…• Sour taste

• Neutralize base

• Dissolves active metal

• Litmus indicator = red

• Definitions– Arrhenius: form H+ in water– Bronsted-Lowry: donates a

proton

About Bases…• Bitter taste

• Neutralize acid

• Feels slippery or “soapy”

• Litmus indicator = blue

• Definitions– Arrhenius: form OH- in water– Bronsted-Lowry: accepts a

proton

Strong Acids & Bases

• Come apart completely in water– Examples: Hydrochloric acid,

sulfuric acid, nitric acid

Weak Acids & Bases

• Come apart only partially in water– Examples: acetic acid, carbonic

acid, hydrocyanic acid

Acids and Bases

Acid/Base Neutralization (Titration)

• Strong acid + strong base

HCl + NaOH H2O + NaCl

NaCl

H+ Cl- Na+ OH-

H2O

pH CalculationspH = – log [H+]

[H+] = 10-pH

• What is the pH of a solution that has a hydrogen ion concentration of 8.5 x 10-4M?

• If a solution has a pH of 9.4, what is the hydrogen ion concentration?

Acids & You• Acid rain

Source: http://www.newint.org/issue114/rain.htm

Acids & You• Digestion

Source: http://www.solvaypharma.ca/en/areas/gastro2.asp

~ 2 liters of stomach acid per day!

Acids & You• In your car

Source: http://newark.rutgers.edu/~huskey/images/lead-acid-battery.gif

Bases & You• Cleaning

– Clarifying shampoos• Higher pH than the hair itself makes

the hair shaft swell and allows cleaning agents to penetrate more deeply

– Detergents• Break up oil and grease

– Drain cleaner• Very high pH to eat through acidic

hair & skin debris

Bases & You• Antacids

– Acid-base neutralization– Calcium carbonate + stomach

acid

Bases & You• Baking

– Baking soda & baking powder react with acid in the batter to form bubbles of CO2

Source: http://www.joyofbaking.com/bakingsoda.html

Practice• Nitric acid (HNO3) reacts with

magnesium hydroxide in an acid-base neutralization reaction.– Write the balanced equation.

– Name both products in the reaction.

2HNO3 + Mg(OH)2 2H2O + Mg(NO3)2

Water and magnesium nitrate

Practice• What is the molarity?

– 50.0g of potassium bromate dissolved in enough water to make 1.5L of solution (2 decimal places)

• How many grams to weigh out?– Make 1.8L of a 0.75M solution of

calcium perchlorate (2 decimal places)

0.2M

322.52g

Practice• What is the percent concentration?

(1 decimal place)– 45mL of ethanol dissolved in 1L of

water

– 85g of NaCl dissolved in 315g of water

4.5% v/v

21.3% m/m

Practice• How many times more acidic is

lemon juice (pH 1.5) than blood (pH 7.5)?

• Something that is 10,000 times more basic than tomatoes (pH 4.2) would have a pH of what?

1,000,000 or 106 times more acidic

pH of 8.2

Practice• What is the pH? (2 decimal

places)– [H+] = 1.87 x 10-4 M

• What is the hydrogen ion concentration?– pH = 11.45

3.73

3.55 x 10-12 M