The Acidic Environment Notes Essay

Submitted By englishstudent111
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Pages: 10

General
Acids
Conducts electricity as ions in solution
An acid is a substance which in solution produces H+ / H3O ions
HX + H2O -> H3O+ + X-
List of common acids:
Hydrochloric acid HCl
Sulfuric acid H2SO4
Nitric acid HNO3
Phosphoric acid H3PO4
Carbonic acid H2CO3
Ethanoic acid CH3COOH
Bases
A base is a substance which either contain the oxide or hydroxide ion or which in solution produces the hydroxide ion
A soluble base is called alkaline
Oxides are insoluble
List of common bases
Calcium hydroxide CaOH
Sodium hydroxide NaOH
Sodium oxide Na2O
Barium hydroxide BaOH2
Calcium oxide CaO
Neutralisation reaction
acid + base -> salt + water
e.g 2HCl + CaO -> CaCl2 + H2O

Syllabus
Notes
9.3.2.2.4
Identify factors which can affect the equilibrium in a reversible reaction
1. Temperature
2. Concentration
3. Pressure/ Volume
Note: catalysts don’t alter the position of a system already in equilibrium. If system is not at equilibrium, catalyst will only help it reach equilibrium faster. It lowers the activation energy and hence increases the reaction rate.
9.5.2.2.1
Explain the effect of changing the following factors on identified equilibrium reactions
9.3.2.2.3
Define Le Chatelier’s Principle
If a system at equilibrium is disturbed by a change, the system will try to minimise the disturbance and establish a new equilibrium
Equilibrium is achieved when the rate of the forward reactions = rate of reverse
Note: liquid water has no direct effect on equilibrium but dilutes ion
9.5.2.2.3
Identify that temperature is the only factor that changes the value of the equilibrium constant K for a given equation
9.3.1.2.1
Classify common substances as acidic, basic or neutral
9.3.1.2.2
Identify that indicators such as…can be used to determine the acidic or basic nature of a material over a range, and that the range is identified by change in indicator colour
Indicators: substance which in solution changes colour depending on whether solution is acidic/alkaline
Using a combination of indicators, we can narrow the range of the pH rather than just acidic or basic
9.3.1.2.3
Describe some everyday uses of indicators including the testing of soil acidity/basicity
Testing soils for
Flower colours
Hydrangeas are blue in acidic soils and pink in alkaline
Some vegetables only grow in a certain pH
Testing swimming pool
Optimal pH required for safety + hygiene
Test local waterways for pollution
9.3.1.3.1
Perform a first-hand investigation to prepare and test a natural indicator
Red cabbage juice, extracted using methanol
Acid- red, purple, green, yellow –Alkaline
Method
1. Obtain a suitable red cabbage
2. Cut into small pieces and grind red cabbage with mortar and pestle
3. Add a small amt. of methanol + boil gently
4. Extract liquid of the red cabbage
5. Calibrate and test
9.3.2.2.1
Identify oxides of non-metals which act as acids and describe the conditions under which they act as acids
Acidic oxides – non-metal oxides
Reacts w/ water to form an acid
CO2(g)+ H2O(l) -> H2CO3(aq) carbonic acid
SO2(g) + H2O(l) -> H2SO3(aq) sulfurous acid
Reacts w/ base to form a salt – neutralisation reaction
Basic Oxide
Reacts w/ acid to form a salt
CuO(s) + H2SO4(aq) -> CuSO4(aq) + H2O(l)
Soluble ones react with water to form alkalis (Group 1)
Na2O(s) + H2O(l) -> 2NaOH(aq)
Amphoteric oxides – reacts with acids + bases
Al2O3, PbO, ZnO, SnO
Basic oxide: Al2O3 + 3H2SO4 -> Al2(SO4)3 (s) + 3H2O(l)
Acidic oxide: Al2O3 + 2Na(AlO2)(aq) + H2O(l)
Neutral oxides – not basic/acidic
CO, NO
9.3.2.2.2
Analyse the position of non-metals in the Periodic Table and outline the relationship between position of elements in the Periodic Table and the acidity/ basicity of oxides
Metal oxides – basic oxides
Non-metal oxides – acidic oxides
Amphoteric oxides are semi metals
9.3.2.2.5
Describe the solubility of CO2 in water under various conditions as an equilibrium process and explain this in terms of Le Chatelier’s Principle
9.3.2.2.6
9.3.2.2.7
Identify natural and