2 - 17 Acids, bases and salt preparations
Salts
● All acids contain hydrogen
● When that hydrogen replaced by metal, compound formed is salt (also
displacement reaction)
●
Reactions involving Mg and acids (displacement reactions)
● .
● (Dilute) H2SO4
○ Rapid fizzing, colourless gas (H2) evolved
■ Ignites with squeaky pop (test for hydrogen)
○ Reaction mixture heated
○ Mg gradually disappears, leaving colourless solution of MgSO4
○ More reactive Mg displaced less reactive hydrogen
● (Dilute) HCl
○ ``` (same as above)
○ ......leaving colourless solution of MgCl2
● ***Anion of acid is spectator ion
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, Reactions of acids
● ***Acid is proton donor, base is proton acceptor
● ***All alkalis are soluble bases
● Simple (dilute) acids react with metals depending on their positions in reactivity
series, ***
○ Below hydrogen - do not react
○ Above hydrogen - react and produce hydrogen gas (H2)
● Acids always split into two separate ions in reactions: hydrogen (positive charge)
and ending anion (negative charge)
Bases
● All neutralization reactions (acid + alkali) are exothermic (give off heat) and
produce water as product
● Most reactions need to be heated in order to start
● E.g.: green copper (II) carbonate reacts with common dilute acids, giving blue\-green
solution
- CO2 given off; test - turns limewater milky/cloudy
○ CuCO3 (s) + H2SO4 (aq) → CuSO4 (aq) + CO2 (g) + H2O (l)
○ CuCO3 (s) + 2HNO3 (aq) → Cu(NO3)2 (aq) + CO2 (g) + H2O (l)
○ CuCO3 (s) + 2HCl (aq) → CuCl2 (aq) + CO2 (g) + H2O (l)
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Salts
● All acids contain hydrogen
● When that hydrogen replaced by metal, compound formed is salt (also
displacement reaction)
●
Reactions involving Mg and acids (displacement reactions)
● .
● (Dilute) H2SO4
○ Rapid fizzing, colourless gas (H2) evolved
■ Ignites with squeaky pop (test for hydrogen)
○ Reaction mixture heated
○ Mg gradually disappears, leaving colourless solution of MgSO4
○ More reactive Mg displaced less reactive hydrogen
● (Dilute) HCl
○ ``` (same as above)
○ ......leaving colourless solution of MgCl2
● ***Anion of acid is spectator ion
1
, Reactions of acids
● ***Acid is proton donor, base is proton acceptor
● ***All alkalis are soluble bases
● Simple (dilute) acids react with metals depending on their positions in reactivity
series, ***
○ Below hydrogen - do not react
○ Above hydrogen - react and produce hydrogen gas (H2)
● Acids always split into two separate ions in reactions: hydrogen (positive charge)
and ending anion (negative charge)
Bases
● All neutralization reactions (acid + alkali) are exothermic (give off heat) and
produce water as product
● Most reactions need to be heated in order to start
● E.g.: green copper (II) carbonate reacts with common dilute acids, giving blue\-green
solution
- CO2 given off; test - turns limewater milky/cloudy
○ CuCO3 (s) + H2SO4 (aq) → CuSO4 (aq) + CO2 (g) + H2O (l)
○ CuCO3 (s) + 2HNO3 (aq) → Cu(NO3)2 (aq) + CO2 (g) + H2O (l)
○ CuCO3 (s) + 2HCl (aq) → CuCl2 (aq) + CO2 (g) + H2O (l)
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