Question 1

How do I calculate molarity of a solution?

Accepted Answer

Molarity (M) = Moles of solute / Volume of solution (L). Moles = Mass (g) / Molar mass (g/mol). For example, dissolving 58.44 g of NaCl (molar mass = 58.44 g/mol) in 1 L of water gives 1 M NaCl. For dilutions: C1V1 = C2V2.

Question 2

How do you calculate pH of a solution?

Accepted Answer

pH = -log₁₀[H⁺], where [H⁺] is hydrogen ion concentration in mol/L. For strong acids: [H⁺] = molarity. For weak acids: [H⁺] = √(Ka × C), where Ka is the acid dissociation constant and C is the concentration. pH 7 is neutral, <7 is acidic, >7 is basic.

Question 3

What is the ideal gas law formula?

Accepted Answer

The ideal gas law: PV = nRT, where P is pressure (Pa or atm), V is volume (m³ or L), n is moles of gas, R is the gas constant (8.314 J/mol·K or 0.0821 L·atm/mol·K), and T is temperature (Kelvin). For real gases, apply van der Waals corrections: (P + a/V²)(V - b) = nRT.

Question 4

How do I calculate heat exchanger LMTD?

Accepted Answer

Log Mean Temperature Difference (LMTD) = (ΔT₁ - ΔT₂) / ln(ΔT₁/ΔT₂), where ΔT₁ and ΔT₂ are the temperature differences at each end of the exchanger. Heat duty Q = U × A × LMTD × F, where U is overall heat transfer coefficient (W/m²·K), A is heat transfer area (m²), and F is LMTD correction factor.

Question 5

How do you calculate reaction conversion and yield?

Accepted Answer

Conversion X = (Moles reacted) / (Moles fed) × 100%. Yield Y = (Moles of desired product) / (Theoretical maximum moles) × 100%. Selectivity S = (Moles of desired product) / (Moles of reactant consumed) × 100%. For nth-order reactions: rate r = k × C^n, where k is rate constant and C is concentration.

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