Chapter 2: Molecules & Solutions

Question 1

What is an ion?

Answer 1

A charged atom that gains or loses electrons to achieve a full outer shell.

Question 2

What rule determines whether atoms give or take electrons?

Answer 2

The octet (or duet) rule – atoms want a full outer shell (usually 8 electrons).

Question 3

When does an atom become a cation?

Answer 3

When it loses electrons → it becomes positively charged.

Question 4

When does an atom become an anion?

Answer 4

When it gains electrons → it becomes negatively charged.

Question 5

Which groups form positive ions (cations)?

Answer 5

Groups 1, 2, 3 → give electrons → +1, +2, +3 charges.

Question 6

Which groups form negative ions (anions)?

Answer 6

Groups 5, 6, 7 → take electrons → -3, -2, -1 charges.

Question 7

What do Group 8 elements do in terms of ion formation?

Answer 7

Nothing—they are stable and don’t form ions (noble gases).

Question 8

What is a molecule?

Answer 8

Two or more atoms chemically bonded together.

Question 9

What are the two parts of a solution?

Answer 9

Solute (dissolved substance) and solvent (does the dissolving).

Question 10

What is the solvent in aqueous solutions?

Answer 10

Always water.

Question 11

What happens to the concentration when you add more solute?

Answer 11

Concentration increases (dissolution).

Question 12

What happens to the concentration when you add more solvent?

Answer 12

Concentration decreases (dilution).

Question 13

What are the 3 main units for concentration?

Answer 13

g/L, %, ppm.

Question 14

What does g/L measure?

Answer 14

Grams of solute per liter of solvent.

Question 15

What does % concentration measure?

Answer 15

Grams of solute per 100 mL of solvent.

Question 16

What does ppm measure?

Answer 16

Grams of solute per 1,000,000 mL of solvent.

Question 17

MATH Q: Convert 30% solution to g/L.

Answer 17

30g/100mL → cross-multiply → 300g/1000mL → Answer: 300 g/L.

Question 18

MATH Q: Convert 225 g/L to %.

Answer 18

225g/1000mL → cross-multiply → 22.5g/100mL → Answer: 22.5%.

Question 19

MATH Q: How much solute is needed for 150 mL of a 4% solution?

Answer 19

(4g/100mL) × 150 → 6g needed.

Question 20

MATH Q: How much solute for 250 mL of a 16 g/L solution?

Answer 20

(16g/1000mL) × 250 → 4g needed.

Question 21

What is an electrolyte?

Answer 21

A substance that conducts electricity when dissolved in water (must break into ions).

Question 22

What is a non-electrolyte?

Answer 22

A substance that does NOT conduct electricity in water.

Question 23

What is the pH scale?

Answer 23

A scale from 0 to 14 measuring how acidic or basic a substance is.

Question 24

pH < 7 means what?

Answer 24

Acid.

Question 25

pH > 7 means what?

Answer 25

Base.

Question 26

pH = 7 means what?

Answer 26

Neutral (like salt or water).

Question 27

What colour does BLUE litmus paper turn in an acid?

Answer 27

RED (BRA = Blue → Red = Acid).

Question 28

What is the formula for acids in water?

Answer 28

Ex: HCl → H⁺ + Cl⁻.

Question 29

What is the formula for bases in water?

Answer 29

Ex: NaOH → Na⁺ + OH⁻.

Question 30

What is a salt?

Answer 30

A compound made of a metal and a non-metal; neutral pH.