Before you can read the parent note on salt hydrolysis, you must own every symbol it throws at you. This page builds each one from nothing — plain words, then a picture, then why the topic needs it. Read top to bottom; every idea leans on the one above it.
Picture a fixed glass box of water. Concentration is just how many particles of one kind are floating in that box. More particles = higher C = more crowded.
Why the topic needs it: every pH formula starts from "we dissolved C moles of salt per litre". The whole calculation is: given this crowd of salt ions, how many H⁺ end up floating? Without C there is nothing to count.
Water is not just sitting still. A tiny fraction of water molecules break apart:
H2O⇌H++OH−
Picture a crowded dance floor: some couples split up (forward) while others pair back up (backward). The number of single dancers holds steady even though individuals keep swapping. That steady mix is equilibrium.
Why the topic needs it: hydrolysis is nothing but this water-splitting balance being nudged. An ion steals some H⁺ or OH⁻, and water responds. You cannot understand the nudge without understanding the resting balance first.
Think of Kw as a fixed budget split between two accounts. If H⁺ goes up, OH⁻ must go down so the product stays 10−14. They see-saw around each other.
In pure water the two are equal, so each is 10−14=10−7 M.
Why the topic needs it: every case ends by asking "so what is [H⁺]?". Kw is the bridge that lets you swap between the acidic side and the basic side of the see-saw.
Concentrations like 10−7 or 7.45×10−6 are awkward. The logarithm fixes that.
Picture a ruler where each equal step means "×10". On that ruler 10−7, 10−6, 10−5 sit at evenly spaced marks −7,−6,−5. The log is just reading off which mark you landed on.
Two log facts the derivations lean on:
log(ab)=loga+logblog(ba)=loga−logb
Picture: multiplying inside a log becomes adding outside it. This is exactly the step where logKbKwC splits into logKw+logC−logKb.
Picture two crowds leaving a stadium. The strong crowd all rush out and never come back. The weak crowd dribbles out slowly, and many keep wandering back inside. That "wanting to go back inside" is the key.
Why the topic needs it: the four cases (SA/SB, SA/WB, WA/SB, WA/WB) are literally the four combinations of strong/weak parents. Everything downstream depends on spotting which parent was weak.
Why the topic needs it: the hydrolysis constant of an ion is always the other member's K divided into Kw. For NH₄⁺ (child of weak base NH₃): Kh=KbKw. This one relationship is what converts a hydrolysis problem into a known Ka or Kb.
