## anonymous one year ago Do strong bases increase pH more than weak bases? Or is it the same?

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1. Ciarán95

A strong base is associated with a higher concentration of OH- ions in solution compared to a weak base. We define pH as (for a weakly concentrated solution anyway): $pH = -\log_{10}[H ^{+} ]$ [H+] is the concentration of H+ ions in solution, or the acidity of the solution (an acid will dissociate in solution to produce H+ ions, or protons are they are often called too). So, this formula results in a lower pH being assigned to a higher H+ correlation and vice versa. So, the higher the concentration of OH- ions in solution, the more H+ ions are effectively 'consumed' by this and there is an increase in the basicity, and thus pH, of the solution. Hope that helps! :)

2. anonymous

So, in essence, Strong Bases have a higher concentration of H+, and therefore have a higher pH levels? @Ciarán95?

3. butterflydreamer

hm.. strong bases have a higher OH- concentration, not a higher H+ concentration. The higher the H+ concentration, the more acidic and therefore the lower the pH level.

4. butterflydreamer

i think to understand this question, you should look at or read about titration graphs and equivalence points :)

5. Ciarán95

@butterflydreamer is correct - a higher pH will result from a solution that is more basic. Perhaps another way to think out it is this.... We usually associate water (H20) as being a highly polar covalent compound. In any sample of water, a process called autoionisation occurs whereby the molecules are in equilibrium with their dissociated ions: $H _{2}O \rightarrow H ^{+} + OH^{-}$ (there should be a double arrow instead of a single arrow above to indicate that the process is in equilibrium). So, a bit like how an ionic compound like NaCl will dissociate in solution to produce an equal number of sodium and chlorine ions, the process also occurs in water (albeit to a lesser extent) by itself. Water typically is classified as being approximately neutral (pH of around 7) and from the above we can see why. Anytime water undergoes autoionsisation the concentration of H+ ions will always the same as the concentration of OH- ions and they effectively cancel each other out in terms of producing a solution that is either acidic or basic. We would associate a base with producing an ionic species which is able to 'mop up' or bind to these H+ ions, thus reducing their excess concentration in solution and increasing the pH. A strong base such as a hydroxyl group (OH-) will tend to be a better proton (H+) acceptor than a weaker base, such as ammonia (NH3). On the other hand, a strong acid will be a better proton donor than a weak acid and will look to dissociate to produce a higher concentration of H+ ions in a solution, thus reducing the pH of that particular solution. Remember, the pH scale is just a theoretical scale of the values which are produced by the formula I mentioned before in my last post. These values depend solely on the concentration of the free H+ ions (or you'll sometimes see it written as H3O+ ions) in solution.