CH. 14 The Mole - CH.19 Solutions

Question 1

**How many molecules are in 2.00 moles of H₂O?
A. 3.01 × 10²³
B. 6.02 × 10²³
C. 1.20 × 10²⁴
D. 2.00 × 10²²

Answer 1

C. 1.20 × 10²⁴

MULTIPLY MOLES X 6.022

Question 2

**How many moles are in 2.00 molecules of H₂O?
A. 3.01 × 10²³
B. 6.60 × 10²³
C. 1.20 × 10²⁴
D. 2.00 × 10²²

Answer 2

B. 6.60 × 10²³
Divide molecules by 6.022

Question 3

How many grams are in 0.5 moles of H₂O? (H = 1, O = 16)
A. 9 g
B. 18 g
C. 27 g
D. 36 g

Answer 3

Answer: A
MULTIPLY MOLES X MOLECULAR WEIGHT OF COMPOUND

Question 4

One mole of a gas at STP occupies how many liters?
A. 22.4 L
B. 24.0 L
C. 18.0 L
D. 20.0 L

Answer 4

Answer: A

Question 5

Which of the following is true about limiting reagents?
A. The reagent that produces the most product is the limiting reagent.
B. The limiting reagent is the one present in greater mass.
C. The reagent that produces the least amount of product is the limiting reagent.
D. Limiting reagents are always in excess.

Answer 5

C because it runs out first

Question 6

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O
How many grams of H₂O are formed from 5 g of C₂H₄? ?

Answer 6

(Molar mass C₂H₄ = 28 g/mol, H₂O = 18 g/mol)
1. Convert to moles:
5 g ÷ 28 g/mol = 0.18 mol C₂H₄
2. Use mole ratio (C₂H₄ : H₂O = 1:2):
0.18 mol × 2 = 0.36 mol H₂O
3. Convert to grams:
0.36 mol × 18 g/mol = 6.48 g H₂O

Question 7

Given: 3Ca + N2 → Ca3N2
If you start with 4.80 moles of Ca and 2 moles of N₂ , which is the limiting reagent?
A. N₂
B. Ca
C. CaN2
D. None, they are equal

Answer 7

Answer: B

for Ca (1/3) = 1.6 runs out first
N2 (1/1) = 2

if it was in grams you would divide by mw to get to moles and then mole ratio

Question 8

Given the reaction:
3Ca + N₂ → Ca₃N₂
If you start with 4.80 mol of Ca and 2.00 mol of N₂,
how many moles of N₂ are left unreacted after the reaction is complete?
Given: Ca - 1.6 mol which is the limiting

Answer 8

starting with N2 given material
2 mol - 1.6 = 0.40 mol is excess

Question 9

Which of the following is a compound?
A. O₂
B. NaCl
C. Air
D. Carbon
Answer:

Answer 9

B. NaCl

Question 10

Which of the following is a molecule according to the DAT?
A. Na⁺
B. AgCl
C. C4H8
D. KBr

Answer 10

C. C4H8 any compound that has a covalent bond diatomic compounds too apart of NO7

Question 11

Which separation technique is best to separate a heterogeneous mixture like sand and water?
A. Distillation
B. Chromatography
C. Filtration
D. Extraction

Answer 11

C. Filtration

Question 12

Which separation technique is best to separate a homogenous mixture like sand and water?
A. Distillation
B. Chromatography
C. Filtration
D. Extraction

Answer 12

A. Distillation

Question 13

Which of the following compounds is insoluble in water?
A. KNO₃
B. NH₄Cl
C. AgBr
D. Na₂SO₄

Answer 13

C. AgBr
Ag⁺ with Br⁻ is PMS exception → not soluble

Question 14

Which compound is always soluble according to the solubility rules?
A. BaSO₄
B. AgCl
C. NaNO₃
D. PbSO₄

Answer 14

C. NaNO₃
Nitrates (NO₃⁻) are always soluble

Question 15

Which compound will form a precipitate when mixed with NaBr?
A. AgNO₃
B. NH₄NO₃
C. KCl
D. Ba(NO₃)₂

Answer 15

A. AgNO₃
Ag⁺ + Br⁻ → AgBr (PMS rule) → forms a precipitate

Question 16

Which of the following will not dissolve in water due to an exception?
A. Na₂S
B. CaSO₄
C. NH₄Cl
D. K₂CO₃

Answer 16

B. CaSO₄
Sulfates with Ca²⁺ = Castro Bear exception → not soluble

Question 17

Which is soluble in water based on the rules?
A. BaCO₃
B. AgBr
C. NH₄Cl
D. PbI₂

Answer 17

C. NH₄Cl
NH₄⁺ compounds are always soluble

Question 18

What best explains why NaNO₃ is soluble in water?
A. It forms a covalent bond
B. It contains a group 7 anion
C. It contains a group 1 cation and nitrate
D. It is nonpolar

Answer 18

C. It contains a group 1 cation and nitrate
Both Na⁺ (Group 1) and NO₃⁻ are always soluble

Question 19

What type of interaction helps ionic compounds dissolve in water?
A. Dipole-dipole
B. London dispersion
C. Ion-dipole
D. Hydrogen bonding

Answer 19

C. Ion-dipole ionic compound + polar

Question 20

What is the net ionic equation for the reaction between Na₂CO₃(aq) and CaCl₂(aq)?
A. Na⁺(aq) + Cl⁻(aq) → NaCl(aq)
B. Ca²⁺(aq) + CO₃²⁻(aq) → CaCO₃(s)
C. Na₂CO₃(aq) + CaCl₂(aq) → CaCO₃(s) + NaCl(aq)
D. Ca²⁺(aq) + Cl⁻(aq) → CaCl₂(s)

Answer 20

B. Ca²⁺(aq) + CO₃²⁻(aq) → CaCO₃(s)
Spectator ions (Na⁺ and Cl⁻) are removed — only the insoluble precipitate CaCO₃ remains.

Question 21

Which of the following are spectator ions in the above reaction?
A. Ca²⁺ and CO₃²⁻
B. Na⁺ and Cl⁻
C. Only Na⁺
D. Only Cl⁻

Answer 21

B. Na⁺ and Cl⁻ do not form the precipitate and remain in solution.

Question 22

Which product forms a precipitate in this reaction?
Na₂CO₃(aq) + CaCl₂(aq) → ?
A. NaCl
B. CaCl₂
C. CaCO₃
D. No precipitate forms

Answer 22

Answer: C
✔️ CaCO₃ is insoluble — you can tell from the solubility rule exception for carbonate salts (unless paired with NH₄⁺ or Group 1).

Question 23

Which of the following would form a supersaturated solution?
A. Salt completely dissolves in water at room temp
B. A hot solution holds more salt than at room temp
C. A mixture separates into layers
D. A precipitate immediately forms when salt is added

Answer 23

Answer: B
✔️ Supersaturated = solution holds more solute due to heating, but it’s unstable.

Question 24

Which of the following is a homogeneous mixture?
A. Oil and water
B. Fruit salad
C. Coffee
D. Sand and salt

Answer 24

Answer: C
✔️ Homogeneous = uniform composition, like coffee (solute and solvent fully dissolved).

Question 25

Which statement is true of a saturated solution? A. It holds less than the max solute B. It holds more than the max solute C. It holds the max solute; any added solute would precipitate D. It can be made only by heating

Answer 25

Answer: C ✔️ Saturated = maximum amount dissolved; excess will precipitate.

Question 26

What happens when a supersaturated solution is cooled and a solid forms? A. It remains supersaturated B. It becomes unsaturated C. It becomes saturated D. The solution becomes heterogeneous

Answer 26

Answer: C ✔️ Precipitation happens → returns to a saturated state.