Andrew's git - notes.git/blob - chem/acids-bases.md

   1# Acids and bases
   2
   3## Examples
   4| name | acid | base |
   5| ---- | ---- | ---- |
   6| Hydrochloric acid | HCl | Cl- |
   7| Sulfuric acid | H2SO4 | HSO4-, SO4 |
   8| Ethanoic acid | CH3COOH | CH3COO- |
   9| Butanoic acid | CH3(CH2)2COOH | CH3(CH2)2COO- |
  10| Nitric acid | HNO3 | NO3- |
  11| Citric acid | C6H8O6 | C6H7O6-, C6H6O6(2-), C6H5O6(3-) |
  12| Propanoic acid | CH3CH2COOH | CH3CH2COO- |
  13| Phosphoric acid | H3PO4 | H2PO4-, HPO4(2-), PO4(3-) |
  14| Hydrogen cyanide | HCN | CN- |
  15| Water | H2O | OH- |
  16| Carbonic acid | H2CO3 | HCO3, CO3(2-) |
  17| Ammonium | NH4+ | NH3 |
  18
  19- monoprotic / diprotic / triprotic - refers to no. of bases
  20
  21- Acid-base reaction: conjugate acid-base pairs (differentiated by one H+)
  22H30+ - hydronium ion
  23
  24- $[x]$ refers to molar concentration of x
  25
  26- _amphiprotic_ - can act as acid or base (e.g. H2O)
  27
  28## Properties of acids
  29
  30- sour taste
  31- corrosive
  32- molecular in structure
  33- dissolves in H2O to produce electrolyte (electric conductor)
  34- neutralised by bases
  35
  36## Acid reactions
  37
  381. acid + metal (exc. Cu, Hg, Ag) $\longrightarrow$ salt + $H_{2(g)}$
  392. acid + metal carbonate $\longrightarrow$ salt + $CO_{2(g)} + H_2O_{(l)}$
  403. acid + metal hydrogen carbonate $\longrightarrow$ salt + $CO_{2(g)} + H_2O_{(l)}$
  414. acid + metal sulfite $\longrightarrow$ salt + $SO_{2(g)} + H_2O_{(l)}$
  425. acid + metal sulfide $\longrightarrow$ salt + $H_2S_{(g)}$
  436. acid + metal oxide (basic oxide) $\longrightarrow$ salt + $H_2O_{(l)}$
  447. acid + base (metal hydroxide) $\rightarrow$ salt + $H_2O_{(l)}$
  45
  46## Properties of bases
  47
  48- bitter taste
  49- slippery feel (reacts with skin oils)
  50- turn litmus red to blue
  51- electrolytes (conductive)
  52- oxides or hydroxides of metal
  53- usually insoluble (insoluble - called _alkali_)
  54
  55## Bronsted-Lowry theory
  56
  57> **Acid:** donates a proton ($H^+$ ion)  r
  58> **Base:** accepts a proton from another substance
  59
  60H atom is one proton and electron, so removing an electron leaves $H^+$ ion.
  61
  62**Only occurs when both acid and base are present**
  63
  64![](http://content.jacplus.com.au/secure/ebooks/07303/0730327531/images/241-1.jpg)
  65
  66## Hydrolysis
  67
  68Hydrolysis is where acid + base react to proudce a non-neutral solution. This happens when ions can act as either acids or bases. aka ionisation reaction.
  69
  70$H_2O_{{(l)}} + H_2O_{(l)} {\longleftrightarrow} {OH}^-_{(aq)} + H_3O^+_{(aq)}$
  71
  72Neutral solutions: $[H_3O^+]=[OH^-]$  
  73Acidic: $[OH^-]<[H_3O^+]$  
  74Basic: $[OH^-]>[H_3O^+]$
  75
  76In all aq solutions at 25C:
  77$$[H_3O^+] \times [OH^-] = 10^{-14} \quad \text{(hydrolysis constant)}$$
  78
  79## Dissociation of bases
  80
  81Ionic bases dissolving in $H_2O$ - ionic compounds dissociate into constituent ions. Not ionised.
  82
  83e.g. $NaOH_{(s)}\stackrel{\mathrm{H_2O}}{\longrightarrow}Na^+_{(aq)}+OH^−_{(aq)}$
  84
  85## pH values
  86
  87Acid/base/neutral not equivalent to pH (logarithmic scale)
  88
  89In water at 25C: $[H_3O^+] \times [OH^-]=10^{-7} \therefore \text{pH}=7$
  90
  91$$\text{pH} = -\log[H_3O^+]=-\log[H^+]$$
  92$$[H_3O^+]=10^{-\text{pH}}$$