Chemistry Midterm Mastery

Solubility

Ionic & Polar solutes dissolve in Polar solvents (Water).

Nonpolar solutes dissolve in Nonpolar solvents.

Speed it Up!

• Stirring
• Increasing Temperature
• Grinding Crystals (Surface Area)

20. When Mg reacts with H\(_2\text{SO}_4\), which gas is evolved?

21. Which solute would be soluble in Hexane (a nonpolar solvent)?
(e.g., NaCl, Mineral Oil, or Water)

22. If solubility is 60g/100g water, what type of solution forms if 150g is added to 200g water?

23. A patient needs 0.072 g of a drug. 12-mg tablets are in stock. How many tablets are given?

24. An isotope of \(^{35}_{17}\text{Cl}\) has how many neutrons?

25. Draw the Lewis Dot Structure for Nitrogen:

26. What is the chemical formula for Magnesium Nitrate?

27. What is the proper IUPAC name for CuCl\(_2\)?

28. Balance the following reaction:
\[\underline{\quad} \text{C}_2\text{H}_4 + \underline{\quad} \text{O}_2 \rightarrow \underline{\quad} \text{CO}_2 + \underline{\quad} \text{H}_2\text{O}\]

29. How many moles are in 25.0 g of NaOH?

30. List one way to increase the rate of solution formation:

Page 1 of 3

Mastering Molecules Key

Atomic Structure & Bonding • Part 3

Part 3

Q11. Identify Reaction: \(2\text{HgO} \rightarrow 2\text{Hg} + \text{O}_2\)

Decomposition

Rationale: Upon applying thermal energy, a single compound (\(\text{HgO}\)) cleanly breaks down into metallic mercury (\(\text{Hg}\)) and oxygen gas (\(\text{O}_2\)).

Q12. Magnesium Electron Config

\(1s^2 2s^2 2p^6 3s^2\) (or 2, 8, 2)

Rationale: Neutral Magnesium has atomic number 12, giving 12 total electrons. They occupy levels from lowest to highest orbital energy.

Q13. Oxygen-18 Isotope Symbol

\(^{18}_{8}\text{O}\)

Rationale: Oxygen always contains 8 protons. An isotope containing 10 neutrons has a combined mass number of 18 (\(8 \text{ protons} + 10 \text{ neutrons} = 18\)).

Q14. Element with 17 Protons

Chlorine (Cl)

Rationale: The atomic number of an element is defined strictly by its number of protons. The element with atomic number 17 on the periodic table is Chlorine.

Q15. Total Electrons in Iodine

53 Electrons

Rationale: In any neutral atom, the negative charge of electrons is balanced by the positive protons. Iodine has atomic number 53, so it has 53 protons and 53 electrons.

Q16. Molar Mass of \(\text{ZnSO}_4\)

\(161.4 \text{ g/mol}\)

Rationale: Mass = \(65.38\text{ (Zn)} + 32.06\text{ (S)} + (4 \times 16.00)\text{ (O)} = 161.44\text{ g/mol}\), which rounds to 4 significant figures as \(161.4\text{ g/mol}\).

Q17. KCl Flame Test Color

Light Purple / Lilac

Rationale: The potassium cation (\(\text{K}^+\)) emits a characteristic light-violet light when its thermally excited valence electrons relax back to their ground states.

Q18. Polarity of \(\text{CO}_2\)

Covalent Compound

Rationale: Both carbon and oxygen are non-metal elements. To bond, they share valence electrons symmetrically, forming covalent bonds rather than transferring ions.

Page 2 of 3

Mastering Molecules Key

Stoichiometry & Solutions • Part 4

Part 4

Q19. Moles of \(\text{O}_2\) for 3.0 Moles \(\text{CH}_4\)

\(6.0 \text{ moles } \text{O}_2\)

Rationale: Equation ratio is \(1\text{ CH}_4 : 2\text{ O}_2\). Therefore, \(3.0\text{ moles } \text{CH}_4 \times (2 / 1) = 6.0\text{ moles } \text{O}_2\).

Q20. Gas evolved: \(\text{Mg} + \text{H}_2\text{SO}_4\)

Hydrogen gas (\(\text{H}_2\))

Rationale: This single-replacement reaction produces hydrogen gas and magnesium sulfate salt: \(\text{Mg} + \text{H}_2\text{SO}_4 \rightarrow \text{MgSO}_4 + \text{H}_2\).

Q21. Soluble in Hexane (Nonpolar)

Mineral Oil

Rationale: Like dissolves like. Hexane is nonpolar, so it dissolves nonpolar solutes like mineral oil, but not polar water or ionic salts.

Q22. Solution state (150g added to 200g)

Saturated with excess solid

Rationale: Max solubility in 200g water is 120g. Adding 150g means 120g dissolves (saturated) and 30g sits at the bottom.

Q23. Dosage: 0.072g Needed (12-mg stock)

6 Tablets

Rationale: \(0.072\text{ g} = 72\text{ mg}\). Total tablets needed is calculated by division: \(72\text{ mg} \div 12\text{ mg/tablet} = 6\text{ tablets}\).

Q24. Neutrons in \(^{35}_{17}\text{Cl}\)

18 Neutrons

Rationale: Neutrons are computed by subtracting atomic number from mass number: \(35 \text{ (mass)} - 17 \text{ (protons)} = 18 \text{ neutrons}\).

Q25. Lewis Dot Structure for Nitrogen

N with 5 valence dots

Rationale: Nitrogen is in group 15, indicating 5 valence electrons. It is represented by one lone pair and three unpaired single dots.

Q26. Formula of Magnesium Nitrate

\(\text{Mg}(\text{NO}_3)_2\)

Rationale: Magnesium forms a \(^{2+}\) cation, while nitrate is \(^{1-}\). Two nitrate polyatomic anions are needed to cancel out the charge.

Q27. IUPAC Name of \(\text{CuCl}_2\)

Copper(II) chloride

Rationale: Chlorine ions have a \(-1\) charge. Two ions equal \(-2\), requiring Copper to be a \(+2\) cation, expressed with roman numerals.

Q28. Balancing \(\text{C}_2\text{H}_4 + \text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

Coefficients: 1, 3, 2, 2

Rationale: Balanced form: \(1\text{C}_2\text{H}_4 + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 2\text{H}_2\text{O}\). Matches atom count (2 C, 4 H, 6 O) on both sides.

Q29. Moles in 25.0g NaOH

0.625 moles

Rationale: Molar mass of \(\text{NaOH}\) is \(40.0\text{ g/mol}\). Moles = \(25.0\text{ g} \div 40.0\text{ g/mol} = 0.625\text{ moles}\) of sodium hydroxide.

Q30. Speed up dissolution

Stirring, heating, grinding solute

Rationale: Agitation exposes fresh solute. Heat increases kinetic energy to break lattice bonds. Grinding increases available surface area.

Page 3 of 3

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CO}_2\), Hexane).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)

Balancing Tip:

Matter cannot be created or destroyed. Coeffecients must make atoms equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses in a formula (g/mol).

Solubility

"Like dissolves Like." Polar (water) dissolves Ionic/Polar. Non-polar (hexane) dissolves Non-polar.

Rate Factors

Faster formation by: Stirring, Increasing Temp, Grinding crystals.

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

Isotope Notation: \(^{70}_{30}\text{Zn}\)

Top # (70) = Mass (P + N)

Bottom # (30) = Protons

Neutrons = 70 - 30 = 40

Bonding & Compounds

Ionic vs. Covalent

Ionic: Metal + Nonmetal (e.g., NaCl). High solubility in water.

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CO}_2\), Hexane).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)

Balancing Tip:

Matter cannot be created or destroyed. Coeffecients must make atoms equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses in a formula (g/mol).

Solubility

"Like dissolves Like." Polar (water) dissolves Ionic/Polar. Non-polar (hexane) dissolves Non-polar.

Rate Factors

Faster formation by: Stirring, Increasing Temp, Grinding crystals.

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

• Combination: 2 parts join
• Decomposition: 1 part splits
• Single Replacement: Swap 1
• Double Replacement: Swap partners

Balancing Rule

"What goes in must come out! Use coefficients to ensure the number of atoms matches on both sides."

Solution Basics

Solubility

Ionic & Polar solutes dissolve in Polar solvents (Water).

Nonpolar solutes dissolve in Nonpolar solvents (e.g., Hexane, CO\(_2\)).

Speed it Up!

• Stirring
• Increasing Temperature
• Grinding Crystals (Surface Area)

Top # (70) = Mass (P + N)

Bottom # (30) = Protons

Neutrons = 70 - 30 = 40

Bonding & Compounds

Ionic vs. Covalent

Ionic: Metal + Nonmetal (e.g., NaCl). High solubility in water.

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CO}_2\), Hexane).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)

Balancing Tip:

Matter cannot be created or destroyed. Coeffecients must make atoms equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses in a formula (g/mol).

Solubility

"Like dissolves Like." Polar (water) dissolves Ionic/Polar. Non-polar (hexane) dissolves Non-polar.

Rate Factors

Faster formation by: Stirring, Increasing Temp, Grinding crystals.

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

Isotope Notation: \(^{70}_{30}\text{Zn}\)

Top # (70) = Mass (P + N)

Bottom # (30) = Protons

Neutrons = 70 - 30 = 40

Bonding & Compounds

Ionic vs. Covalent

Ionic: Metal + Nonmetal (e.g., NaCl). High solubility in water.

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CO}_2\), Hexane).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)
• Combustion: Fuel + \(\text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

Balancing Tip:

Matter cannot be created or destroyed. Coefficients must make atoms equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses in a formula (g/mol).

Solubility

"Like dissolves Like." Polar (water) dissolves Ionic/Polar. Non-polar (hexane) dissolves Non-polar.

Rate Factors

Faster formation by: Stirring, Increasing Temp, Grinding crystals.

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

Isotope Notation: \(^{70}_{30}\text{Zn}\)

Top # (70) = Mass (P + N)

Bottom # (30) = Protons

Neutrons = 70 - 30 = 40

Bonding & Compounds

Ionic vs. Covalent

Ionic: Metal + Nonmetal (e.g., NaCl). High solubility in water.

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CH}_4\), Hexane).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)
• Combustion: Fuel + \(\text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

Balancing Tip:

Matter cannot be created or destroyed. Atoms must be equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses (g/mol).

Solubility Rules

"Like dissolves Like."

• • Polar/Ionic: Soluble in Water
• • Non-polar: Soluble in Hexane
• • Non-polar: NOT soluble in Water

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

Isotope Notation: \(^{70}_{30}\text{Zn}\)

Top # (70) = Mass Number (P + N)

Bottom # (30) = Protons

Neutrons = 70 - 30 = 40

Bonding & Compounds

Ionic vs. Covalent

Ionic: Metal + Nonmetal (e.g., NaCl). High solubility in water.

Covalent: Nonmetal + Nonmetal (e.g., \(\text{CO}_2\)).

Naming Rules

Transition metals need Roman Numerals: \(\text{Fe}_2(\text{SO}_4)_3\) is Iron(III) Sulfate.

Chemical Reactions

Types:

• Combination: \(A + B \rightarrow AB\)
• Decomposition: \(AB \rightarrow A + B\)
• Single Replacement: \(A + BC \rightarrow AC + B\)
• Double Replacement: \(AB + CD \rightarrow AD + CB\)
• Combustion: Fuel + \(\text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

Balancing Tip:

Matter cannot be created or destroyed. Atoms must be equal on both sides!

Solutions & Moles

Molar Mass

Sum of all atomic masses (g/mol).

Solubility Highlights

• • Polar/Ionic (NaCl, Sugar) → Soluble in Polar (Water)
• • Non-Polar (Oil, \(\text{CO}_2\)) → Soluble in Non-Polar (Hexane)
• • Non-Polar molecules are NOT soluble in Water!

Final Review Checklist

Sig Fig Rules

Polyatomic Ions

Reaction Types

Covalent: Nonmetal + Nonmetal (e.g. CO2, Hexane).

Chemical Reactions

Combination

A + B → AB

Decomposition

AB → A + B

Combustion

Fuel + O2 → CO2 + H2O

Note: Use coefficients to balance atoms on both sides!

Solubility Rules

"Like Dissolves Like"

• Polar/Ionic dissolve in Water
• Nonpolar dissolve in Hexane

Crucial Fact

Non-polar substances (like Oil or CO2) are NOT soluble in water!

Sig Fig Rules Density Math Bonding Types

Solubility Rules

"Like Dissolves Like"

• Polar/Ionic dissolve in Water

• Non-polar dissolve in Hexane

Critical Fact

Non-polar molecules (like CO2 or Oil) are NOT SOLUBLE in water!

Reactions

Decomp: AB → A + B

Comb: Fuel + \(\text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

*Balance atoms with coefficients!

Solubility Rules

"Like Dissolves Like"

• Polar/Ionic dissolve in Water
• Nonpolar dissolve in Hexane

Important

Non-polar molecules (like CO2 or Oil) are NOT SOLUBLE in water!

Solubility Rules

"Like Dissolves Like"

• Polar/Ionic dissolve in Water

• Non-polar dissolve in Hexane

Critical Fact

Non-polar molecules (like CO2 or Oil) are NOT SOLUBLE in water!

Reactions

Decomp: AB → A + B

Combustion: Fuel + \(\text{O}_2 \rightarrow \text{CO}_2 + \text{H}_2\text{O}\)

Solubility Rules

"Like Dissolves Like"

• Polar/Ionic dissolve in Water

• Non-polar dissolve in Hexane

CRITICAL FACT

Non-polar molecules (like CO2 or Oil) are NOT SOLUBLE in water!

CRITICAL MIDTERM TIP

Non-polar molecules (like CO2 or Oil) are NOT SOLUBLE in water!