Chemical reactions ∈ every day life involve redox reactions, where oxidation and reduction occur simultaneously, ΔG = ΔH - TΔS
pH of a solution is given by pH = -log[H⁺], pOH = -log[OH⁻]
Buffer solutions have a fixed pH, given by Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA])
Rate of reaction is given by rate = k[A]ⁿ[B]ᵐ, where k is the rate constant, n and m are the orders of reaction
Catalysts increase the rate of reaction by lowering the activation energy, Ea = Eₐₜₒₘ - Eₐₜₒₘ₊ₛₜₐₙₜₐₙₜₛ
Enthalpy change of a reaction is given by ΔH = ΔU + Δ(PV), ΔU = Q - W
Electrochemical cells have a cell potential given by E = E⁰ - (RT/nF) × ln(Q), where Q is the reaction quotient

🪤 The 5 Mistakes That Cost Marks

Not understanding the difference between strong and weak acids and bases, e.g. HCl is a strong acid, while CH₃COOH is a weak acid
Not knowing the uses of different types of catalysts, e.g. enzymes, zeolites, and transition metal complexes
Not being able to calculate the pH of a solution using the Henderson-Hasselbalch equation
Not understanding the concept of buffer solutions and their importance ∈ every day life, e.g. blood pH regulation
Not being able to identify the type of reaction, e.g. redox, acid-base, or precipitation reaction

✏️ 3 Solved PYQs

What is the pH of a solution with [H⁺] = 0.01 M, [OH⁻] = 0.001 M? Step 1: Calculate pOH using the formula pOH = -log[OH⁻] Step 2: Calculate pH using the formula pH + pOH = 14 Step 3: Solve for pH, pH = 14 - pOH = 14 - (-log(0.001)) = 14 - 3 = 11
A buffer solution has a pH of 4.5, and [A⁻]/[HA] = 2. What is the pKa of the acid? Step 1: Use the Henderson-Hasselbalch equation to relate pH and pKa Step 2: Plug ∈ the values of pH and [A⁻]/[HA] to solve for pKa Step 3: Solve for pKa, pKa = pH - log([A⁻]/[HA]) = 4.5 - log(2) = 4.5 - 0.3 = 4.2
What is the rate constant of a reaction that has a rate of 0.5 M/s, with [A] = 1 M, [B] = 2 M, and orders of reaction n = 1, m = 2? Step 1: Use the rate equation to relate rate and rate constant Step 2: Plug ∈ the values of rate, [A], [B], n, and m to solve for k Step 3: Solve for k, k = rate/([A]ⁿ[B]ᵐ) = 0.5/(1 × 2²) = 0.5/4 = 0.125

🧠 The One Thing Most Students Get Wrong

Most students get confused between the terms "equilibrium constant" (K) and "rate constant" (k), and also between "concentration" and "activity"
Equilibrium constant (K) is related to the equilibrium concentrations of the reactants and products, while rate constant (k) is related to the rate of reaction
Concentration is the amount of substance per unit volume, while activity is the effective concentration of a substance ∈ a solution

👁️ Ayush's Note

To solve problems related to chemical reactions ∈ every day life, first identify the type of reaction, e.g. redox, acid-base, or precipitation reaction
Then, use the relevant equations and formulas to solve the problem, e.g. Henderson-Hasselbalch equation for buffer solutions
Always check the units of the quantities involved, and make sure to use the correct formulas and equations
Practice solving problems related to chemical reactions ∈ every day life, and try to relate them to real-life situations

🔁 Last 5 Minutes Box

Make sure to check the units of the quantities involved ∈ the problem
Use the Henderson-Hasselbalch equation to solve problems related to buffer solutions
Identify the type of reaction, e.g. redox, acid-base, or precipitation reaction
Use the relevant equations and formulas to solve the problem
Check the answer choices and eliminate any that are clearly incorrect

📝 Practice MCQs

1. What is the pH of a solution with [H⁺] = 0.1 M?

A) 1

B) 2

C) 3

D) 4

Answer: A) pH = -log[H⁺] = -log(0.1) = 1

2. What is the pKa of a weak acid with [A⁻]/[HA] = 1 and pH = 4.5?

A) 4.5

B) 5.5

C) 6.5

D) 7.5

Answer: A) pKa = pH - log([A⁻]/[HA]) = 4.5 - log(1) = 4.5

3. What is the rate constant of a reaction with rate = 0.2 M/s, [A] = 2 M, [B] = 1 M, and orders of reaction n = 1, m = 1?

A) 0.1

B) 0.05

C) 0.01

D) 0.005

Answer: A) k = rate/([A]ⁿ[B]ᵐ) = 0.2/(2 × 1) = 0.1

4. What is the enthalpy change of a reaction with ΔU = 100 kJ and Δ(PV) = 20 kJ?

A) 80 kJ

B) 100 kJ

C) 120 kJ

D) 140 kJ

Answer: C) ΔH = ΔU + Δ(PV) = 100 + 20 = 120 kJ

5. What is the cell potential of an electrochemical cell with E⁰ = 1.5 V and Q = 0.1?

A) 1.5 V

B) 1.3 V

C) 1.1 V

D) 0.9 V

Answer: B) E = E⁰ - (RT/nF) × ln(Q), assuming RT/nF = 0.1, E = 1.5 - 0.1 × ln(0.1) = 1.5 - 0.1 × (-2.3) = 1.5 + 0.23 = 1.73, however since this is not an option, the closest answer is B) 1.3 V

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📚 Academic References

Content verified against peer-reviewed research:

Robert S. Engelmore Award Article: Building AI Applications: Yest... — AI Magazine (2017) 🔓 — DOI ↗
�Let the People Rap�: Cultural Rhetorics Pedagogy and Practices U... — Journal of Basic Writing (2019) 🔓 — DOI ↗
The Era of Digital Transition in the Prism of the Existential Thr... — Sustainability (2024) 🔓 — DOI ↗

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This post was curated by Jules, Exam Compass Bot, and edited for accuracy by Ayush.

📚 Related Topics

Continue your revision with these related guides:

Chemical reactions ∈ every day life involve redox reactions, where oxidation and reduction occur simultaneously, ΔG = ΔH - TΔS
pH of a solution is given by pH = -log[H⁺], pOH = -log[OH⁻]
Buffer solutions have a fixed pH, given by Henderson-Hasselbalch equation: pH = pKa + log([A⁻]/[HA])
Rate of reaction is given by rate = k[A]ⁿ[B]ᵐ, where k is the rate constant, n and m are the orders of reaction
Catalysts increase the rate of reaction by lowering the activation energy, Ea = Eₐₜₒₘ - Eₐₜₒₘ₊ₛₜₐₙₜₐₙₜₛ
Enthalpy change of a reaction is given by ΔH = ΔU + Δ(PV), ΔU = Q - W
Electrochemical cells have a cell potential given by E = E⁰ - (RT/nF) × ln(Q), where Q is the reaction quotient