Acids, Bases, pH, and Titration Study Guide for GOB College Chemistry

Q1. Define the following: Arrhenius Acid, Arrhenius Base, Brønsted–Lowry Acid, Brønsted–Lowry Base.

Background

Topic: Acid-Base Theory

This question tests your understanding of the fundamental definitions of acids and bases according to two major theories: Arrhenius and Brønsted–Lowry.

Key Terms:

• Arrhenius Acid: Substance that increases H+ concentration in water.

• Arrhenius Base: Substance that increases OH- concentration in water.

• Brønsted–Lowry Acid: Proton (H+) donor.

• Brønsted–Lowry Base: Proton (H+) acceptor.

Step-by-Step Guidance

1. Recall the Arrhenius definition: Acids produce H+ ions, bases produce OH- ions in aqueous solution.

2. Recall the Brønsted–Lowry definition: Acids donate protons, bases accept protons.

3. Think about examples for each definition (e.g., HCl for Arrhenius acid, NH3 for Brønsted–Lowry base).

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Q2. When a hydrogen atom loses an electron, it becomes a: ____________.

Background

Topic: Atomic Structure

This question tests your understanding of what happens to a hydrogen atom when it loses its only electron.

Key Terms:

• Hydrogen atom: 1 proton, 1 electron.

• Ion: Atom or molecule with a net charge.

Step-by-Step Guidance

1. Consider the composition of a hydrogen atom (proton + electron).

2. When the electron is lost, only the proton remains.

3. Think about what this particle is called in chemistry.

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Q3. Water naturally forms: ____________ and ____________ ions.

Background

Topic: Autoionization of Water

This question tests your knowledge of the ions produced when water autoionizes.

Key Terms:

• Autoionization: Water molecules react to form ions.

• Hydronium ion ($\text{H}_3\text{O}^+$) and hydroxide ion ($\text{OH}^-$).

Step-by-Step Guidance

1. Recall the autoionization equation: $\text{H}_2\text{O} + \text{H}_2\text{O} \rightarrow \text{H}_3\text{O}^+ + \text{OH}^-$.

2. Identify the two ions formed.

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Q4. Write products of acid or base dissociation and balance the equation as needed:

• H2SO4 → ____________

• HCl → ____________

• H3PO4 → ____________

• CH3COOH → ____________

Background

Topic: Acid/Base Dissociation

This question tests your ability to write dissociation equations for common acids and bases.

Key Terms:

• Dissociation: Splitting of a compound into ions in solution.

• Balance: Ensure charge and atom balance in equations.

Step-by-Step Guidance

1. Write the formula for each acid or base.

2. Determine the ions produced upon dissociation.

3. Balance the equation for charge and atoms.

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Q5. Know properties of acids and bases.

Background

Topic: Properties of Acids and Bases

This question tests your knowledge of the physical and chemical properties of acids and bases.

Key Terms:

• Acids: Sour taste, react with metals, turn litmus red.

• Bases: Bitter taste, slippery feel, turn litmus blue.

Step-by-Step Guidance

1. List common properties for acids (taste, reactivity, color change).

2. List common properties for bases (taste, feel, color change).

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Q6. Translate the name of a substance into its molecular formula.

• HNO3 → ____________

• NH3 → ____________

• HF → ____________

• H2CO3 → ____________

• Ca(OH)2 → ____________

• H3PO4 → ____________

• HBr → ____________

• CH3COOH → ____________

• Fe(OH)3 → ____________

• HCl → ____________

Background

Topic: Chemical Nomenclature

This question tests your ability to match compound names to their molecular formulas.

Key Terms:

• Nomenclature: System for naming chemical compounds.

• Formula: Representation of elements and their ratios.

Step-by-Step Guidance

1. Recall the rules for naming acids and bases.

2. Match each name to its correct formula.

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Q7. Practice: Complete the following equations

• Autoionization of water: H2O + H2O →

• Carbonic acid mixed with water (donates 1 proton) →

• Hydroiodic acid mixed with water →

• Full dissociation of potassium hydroxide →

• Partial dissociation of lead (II) hydroxide →

• Formation of acetic acid →

• Formation of ammonium when ammonia is mixed in water →

Background

Topic: Chemical Reactions and Dissociation

This question tests your ability to write and complete chemical equations for acid/base reactions.

Key Terms:

• Dissociation: Separation into ions.

• Formation: Combination to produce a compound.

Step-by-Step Guidance

1. Write the reactants for each equation.

2. Determine the products based on the type of reaction (acid/base, dissociation, formation).

3. Balance the equation for atoms and charge.

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Q8. The pH scale measures ____________. Neutral pH = ____. Acidic range = ________ to ________. Basic range = ________ to ________.

Background

Topic: pH Scale

This question tests your understanding of what the pH scale measures and the ranges for acidic, neutral, and basic solutions.

Key Terms and Formulas:

• pH: Measure of hydrogen ion concentration.

• Neutral pH: 7

• Acidic: pH < 7

• Basic: pH > 7

Step-by-Step Guidance

1. Recall what pH measures (hydrogen ion concentration).

2. Identify the value for neutral pH.

3. Determine the ranges for acidic and basic solutions.

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Q9. Concept Questions: Why is the pH scale logarithmic? What is a diprotic acid? What is a monobasic base? What happens to pH when hydrogen ion concentration increases? Why is even a small change in pH important in biological systems? Why do antacids reduce heartburn? Human blood is slightly basic. Why is this important? A hydrangea plant changes flower color due to:

Background

Topic: Acid/Base Concepts and Biological Relevance

This question tests your understanding of pH, acid/base types, and their importance in biological and chemical systems.

Key Terms:

• Logarithmic scale: Each unit change is a tenfold change in concentration.

• Diprotic acid: Can donate two protons.

• Monobasic base: Can accept one proton.

Step-by-Step Guidance

1. Explain why pH is logarithmic (concentration changes by powers of ten).

2. Define diprotic acid and monobasic base.

3. Describe the effect of increasing hydrogen ion concentration on pH.

4. Discuss the importance of pH in biological systems.

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Q10. pH Calculations: [H+] = 1.0 × 10⁻³ M → pH = ____________. pH = 4.0 → [H+] = ____________. [OH-] = 1.0 × 10⁻⁵ M → pOH = ____________ → pH = ____________.

Background

Topic: pH and pOH Calculations

This question tests your ability to calculate pH, pOH, and ion concentrations using logarithmic relationships.

Key Formulas:

• $\text{pH} = -\log_{10}[\text{H}^+]$

• $\text{pOH} = -\log_{10}[\text{OH}^-]$

• $\text{pH} + \text{pOH} = 14$

• $[\text{H}^+] = 10^{-\text{pH}}$

• $[\text{OH}^-] = 10^{-\text{pOH}}$

Step-by-Step Guidance

1. For each calculation, identify the formula needed (logarithmic or exponential).

2. Plug in the given values and set up the calculation.

3. For pH and pOH, remember to use base 10 logarithms.

4. For conversions, use $\text{pH} + \text{pOH} = 14$.

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Q11. Find the pH of a solution containing 0.04M hydrocyanic acid. Is HCN a strong or a weak acid?

Background

Topic: Weak Acid pH Calculation

This question tests your ability to calculate the pH of a weak acid solution and classify the acid's strength.

Key Terms and Formulas:

• Weak acid: Does not fully dissociate.

• Ka: Acid dissociation constant.

• $\text{HCN} \rightleftharpoons \text{H}^+ + \text{CN}^-$

• $\text{Ka} = \frac{[\text{H}^+][\text{CN}^-]}{[\text{HCN}]}$

Step-by-Step Guidance

1. Write the dissociation equation for HCN.

2. Set up the ICE table (Initial, Change, Equilibrium) for concentrations.

3. Use the Ka value for HCN from the table.

4. Set up the equation $\text{Ka} = \frac{x^2}{0.04 - x}$, where x is [H+].

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Q12. Find the pH of a solution containing 0.3M methylamine. Is CH3NH2 a strong or a weak base?

Background

Topic: Weak Base pH Calculation

This question tests your ability to calculate the pH of a weak base solution and classify the base's strength.

Key Terms and Formulas:

• Weak base: Does not fully dissociate.

• Kb: Base dissociation constant.

• $\text{CH}_3\text{NH}_2 + \text{H}_2\text{O} \rightleftharpoons \text{CH}_3\text{NH}_3^+ + \text{OH}^-$

• $\text{Kb} = \frac{[\text{CH}_3\text{NH}_3^+][\text{OH}^-]}{[\text{CH}_3\text{NH}_2]}$

Step-by-Step Guidance

1. Write the dissociation equation for methylamine.

2. Set up the ICE table for concentrations.

3. Use the Kb value for methylamine from the table.

4. Set up the equation $\text{Kb} = \frac{x^2}{0.3 - x}$, where x is [OH-].

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Q13. What is the concentration of hydronium ions when a solution pH is 2.33?

Background

Topic: pH and Ion Concentration

This question tests your ability to convert pH to hydronium ion concentration.

Key Formula:

• $[\text{H}_3\text{O}^+] = 10^{-\text{pH}}$

Step-by-Step Guidance

1. Identify the formula for hydronium ion concentration.

2. Plug in the pH value to the formula.

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Q14. Find [H+] and pH of a weak monoprotic acid that has: Ka = 2.2 × 10⁻⁶, Initial acid concentration = 0.135 M

Background

Topic: Weak Acid Equilibrium

This question tests your ability to use the acid dissociation constant (Ka) to find equilibrium concentrations and pH.

Key Formula:

• $\text{Ka} = \frac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}$

Step-by-Step Guidance

1. Write the dissociation equation for the acid.

2. Set up the ICE table for concentrations.

3. Use the Ka value and initial concentration to set up the equation $\text{Ka} = \frac{x^2}{0.135 - x}$.

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Q15. Find [OH-], pOH, and pH of a weak monobasic base that has: Kb = 3.1 × 10⁻⁹, Concentration = 0.07 M

Background

Topic: Weak Base Equilibrium

This question tests your ability to use the base dissociation constant (Kb) to find equilibrium concentrations, pOH, and pH.

Key Formula:

• $\text{Kb} = \frac{[\text{OH}^-][\text{BH}^+]}{[\text{B}]}$

Step-by-Step Guidance

1. Write the dissociation equation for the base.

2. Set up the ICE table for concentrations.

3. Use the Kb value and initial concentration to set up the equation $\text{Kb} = \frac{x^2}{0.07 - x}$.

4. Once you solve for x ([OH-]), use $\text{pOH} = -\log_{10}[\text{OH}^-]$ and $\text{pH} = 14 - \text{pOH}$.

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Q16. Calculate Q, compare Q to Ka, and state direction of shift for the following:

• [H+] = 1.5 × 10⁻³ M, [A-] = 2.5 × 10⁻³ M, [HA] = 0.25 M, Ka = 1.1 × 10⁻⁵

• [OH-] = 1.48 × 10⁻⁷ M, [BH+] = 1.48 × 10⁻⁷ M, [B] = 0.1 M, Kb = 2.2 × 10⁻¹³

• [OH-] = 1.5 × 10⁻³ M, [BH+] = 1.5 × 10⁻³ M, [B] = 0.05 M, Kb = 9.3 × 10⁻¹²

Background

Topic: Reaction Quotient and Equilibrium

This question tests your ability to calculate the reaction quotient (Q), compare it to the equilibrium constant (Ka or Kb), and predict the direction of the reaction shift.

Key Formula:

• $Q = \frac{[\text{products}]}{[\text{reactants}]}$

• Compare Q to Ka or Kb: If Q < K, reaction shifts right; if Q > K, reaction shifts left.

Step-by-Step Guidance

1. Calculate Q for each scenario using the given concentrations.

2. Compare Q to Ka or Kb.

3. Predict the direction of the reaction shift based on the comparison.

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Q17. Plot the titration curve for Fe(OH)3 + HCl and label all its parts. Assume 1 equivalence point.

Background

Topic: Titration Curves

This question tests your ability to interpret and label a titration curve for a weak base and strong acid reaction.

Key Terms:

• Titration: Gradual addition of one solution to another to determine concentration.

• Equivalence point: Point where stoichiometric amounts of acid and base have reacted.

Step-by-Step Guidance

1. Draw the axes: pH (y-axis) vs. volume of titrant (x-axis).

2. Mark the starting pH (weak base).

3. Identify the equivalence point and label it.

4. Label regions: before, at, and after equivalence point.

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