Acids & BasesChapter 14

West Valley High SchoolGeneral Chemistry

Mr. Mata

Standard 5C

• Students will know the observable properties of acids, bases, & salts.

Essential Question:

What are the general

properties of acids

and bases?

PROPERTIES OF ACIDS• General formula of acid is HX.• Sour taste; corrosive; contain H +1 (hydrogen ions).• Aqueous solutions are electrolytes.• Cause indicators to change color:

– BLUE LITMUS PAPER + ACID -> RED COLOR

• React with some metals to produce H2(g).

• React with bases to produce salt & water.• pH = 0 to 6.9999 on pH scale. • Ex: vinegar, citrus fruits

Properties of Bases• General formula XOH (where X is a metal).

• Taste bitter; corrosive; OH -1 (hydroxide ions).

• Feel slippery to touch.

• Cause indicators to change color:– RED LITMUS PAPER + BASE -> BLUE COLOR

• Aqueous solutions are electrolytes.

• React with acids to produce salt and water.

• pH = 7.0001 – 14 on pH scale.

• Ex: ammonia, lye

Neutralization Reaction• Acid + Base -> Salt + Water

• ex: HCl + NaOH -> NaCl + H2O

• H + 1 ion combines with OH -1 ion -> H2O.

• Na +1 ion combines with Cl -1 ion -> NaCl.

• H2O is neutral with pH = 7.000

Arrhenius Acids and Bases• Svante Arrhenius (1884) proposed theory

of ionization for acids & bases.• Definition

- Acids release hydrogen ions (H +1).

- Bases release hydroxide ions (OH -1).

Arrhenius Acids and Bases• Acids may be mono, di, or tri protic.

• Nitric acid (HNO3) = ? H +1 ion

• 1 H +1 ion = monoprotic acid

• Sulfuric acid (H2SO4) = ? H +1 ion

• 2 H +1 ions = diprotic acid

• Phosphoric acid (H3PO4) = ? H +1 ion

• 3 H +1 ions = triprotic acid

Bronsted-Lowry Acids and Bases• Bronsted-Lowry acid = H +1 ion donor.• Bronsted-Lowry base = H +1 ion acceptor. H +1

• Ex: H2O + NH3 -> OH -1 + NH4 +1

acid base

Meaning of pH• pH = “power of hydrogen”.

• Acids have pH from 0 to 6.9999.

• A neutral solution has a pH of 7.0000

• Bases have pH from 7.0001 to 14.

• pH + pOH = 14

• “[ ]” = concentration or molarity • [H+ 1] x [OH- 1] = 1 x 10 -14 M

The pH Concept

• Express large [H+ 1] ion concentrations using smaller numbers.

• Logrithmic scale (base 10 units).

• pH = - log [H+ 1]• [H+] = 1 x 10 –3 M -> pH = 3 (acidic)• [H+] = 1 x 10 –7 M -> pH = 7 (neutral)• [H+] = 1 x 10 –11 M -> pH = 11 (basic)

The pH Scale

• 1 pH unit change = 10x change• pH > 7 basic• pH = 7 neutral• pH < 7 acidic

Measuring pH• Variety of different indicators.• Indicators are acids or bases that change color with the

changing [H+1].• Phenol Red (swimming pools) and phenolphthalein

(trace blood). • Can use pH meter, litmus paper (red or blue), pH paper.

Chapter 14 SUTW Prompt

• Describe how acids and bases are organized on the pH scale.

• Complete a 8 -10 sentence paragraph using the SUTW paragraph format. Hilight using green, yellow, and pink.

• Due Date: Tomorrow (start of class).