Chap. 10: pH, Acids, and Bases

Question 1

pH

Answer 1

Per Hydrogen.

The measure of the concentration of H⁺ in a solution.

Question 2

Acid

Answer 2

Donate H⁺ ions into a solution.

For example:

HCl → H⁺ + Cl^-

Acids also come in different strengths. The more moles of H⁺, the stronger the acid.

Question 3

Base

Answer 3

There are two ways to define bases:

1.) Put OH^- into a solution.

NaOH → Na⁺ + OH^-

2.) Remove H⁺ from a solution.

NH₃ + H₂O ⇔ NH₄⁺ + OH^-

Question 4

H⁺ Ions

Answer 4

Acidic.

Increase in H⁺, decrease in OH^-.

Question 5

OH^- Ions

Answer 5

Basic.

Increase in OH^-, decrease in H⁺.

Question 6

pH and Water

Answer 6

Water and H⁺ and OH^- will go back and forth with each other until a state of equilibrium is reached.

H₂O ⇔ H⁺ + OH^-

or

H₂O + H₂O ⇔ H₃O⁺ + OH^-

(Both of these are correct, both are used)

Question 7

pH Scale

Answer 7

Acidic (more H⁺ ions) = pH of -1 to 6

10¹ = –1 (concentrated HCl)

10⁰ = 0 (battery acid)

10^-1 = 1 (lemon juice)

10^-3 = 3 (vineger, soft drink, beer)

10^-4 = 4 (tomato, coffee)

10^-5 = 5 (urine, rainwater)

10^-6 = 6 (milk)

*Neutral* 10^-7 = 7 (pure water, blood, seawater)

10^-8 = (seawater)

10^-9 = 9 (baking soda)

10^-10 = 10 (soap)

10^-11 = 11 (ammonia)

10^-12 = 12 (hair remover)

10^-13 = 13 (oven cleaner)

Basic (more OH^- ions) = pH of 8 to 14

Question 8

Acids and Bases

Answer 8

HCl + NaOH → H₂O (l) + NaCl

*This is also a double-displacement reaction.

1 mole HCl + 1 mole NaOH → 1 mole H2O

2 moles HCl + 4 moles NaOH → Basic

Question 9

pH = -log₁₀[H⁺]

Answer 9

H₂O ⇔ H⁺ + OH^-

1 in every 10 million water molecules are reacting this way. Therefore:

pH = -log₁₀[H⁺]

Question 10

What is the pH of a solution that has a hydronium-ion concentration of 0.001M?

Answer 10

The number 0.001 is 10^-3 (by moving the decimal point three places to the right), therefore:

pH = – log [H₃O⁺]

= – log [10^-3]

= – ( –3)

pH​ = 3

Question 11

What is the pH of a 0.01M solution of HCl?

Answer 11

The number 0.01 is 10^-2 (by moving the decimal point two places to the right), therefore:

pH = – log [H₃O⁺]

= – log [10^-2]

= – ( –2)

pH​ = 2

Question 12

What is the pH of a 0.000001M solution of HCl?

Answer 12

The number 0.0000001 is 10^-6 (by moving the decimal point six places to the right), therefore:

pH = – log [H₃O⁺]

= – log [10^-6]

= – ( –6)

pH​ = 6

Question 13

What is the pH of a 0.01M solution of NaOH?

Answer 13

Since NaOH is a base, we are going to start from the basic end of the pH Scale.

0.01M is 10^-2

Starting from the very basic 14, we subtract 2 to get the pH.

pH = 12