JEE: pH 1 Solution Diluted — New pH? 💡
❓ Question An aqueous solution of HCl has: p H = 1 pH = 1 The solution is diluted by adding equal volume of water . Find the new pH of the solution. (Ignore dissociation of water.) 🖼 Question Image ✍️ Short Concept pH is related to hydrogen ion concentration: p H = − log [ H + ] pH = -\log[H^+] Dilution reduces concentration → pH increases. 🔷 Step 1 — Find Initial [ H + ] [H^+] [ H + ] 💯 Given: p H = 1 pH = 1 [ H + ] = 10 − 1 M [H^+] = 10^{-1} \, M Since HCl is strong acid , it dissociates completely. 🔷 Step 2 — Apply Dilution Rule Equal volume of water added ⇒ Total volume becomes double . So concentration becomes half . [ H + ] n e w = 10 − 1 2 [H^+]_{new} = \frac{10^{-1}}{2} = 5 × 10 − 2 = 5 \times 10^{-2} 🔷 Step 3 — Calculate New pH p H = − log ( 5 × 10 − 2 ) pH = -\log(5 \times 10^{-2}) = − [ log 5 + log 10 − 2 ] = -[\log5 + \log10^{-2}] = − ( 0.699 − 2 ) = -(0.699 - 2) = 1.30 = 1.30 🔷 Step 4 — Concept Shortcut When concentration h...