Acids, Bases and Salts Flashcards
List two properties of acids and bases.
Acids
* Acids have a sour taste
* Acids turn the colour of litmus from blue to red.
Bases
* Bases have a bitter taste
* Bases turn the colour of litmus from red to blue.
What is litmus paper?
Litmus solution is a purple dye, which is extracted from lichen, a plant belonging to the division Thallophyta, and is commonly used as an indicator. When the litmus solution is neither acidic nor basic, its colour is purple.
List some natural indicators
Natural indicators are substances obtained from natural sources that can be used to determine whether a solution is acidic or basic based on their color changes. Examples include turmeric which turns red in bases and remains yellow in acids, and litmus paper which red in acids and blue in bases.
What are olfactory indicators? Give examples.
These indicators tell us whether a substance is acidic or basic by change in colour. There are some substances whose odour changes in acidic or basic media. These are called olfactory indicators.
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How do acids react with metals?
Zn ( s ) + H 2 SO 4 ( aq ) → ZnSO 4 ( aq ) + H 2 ( g )
The metal in the above reaction displaces hydrogen atoms from the acids as hydrogen gas and forms a compound called a salt. Thus, the reaction of a metal with an acid can be summarised as –
Acid + Metal → Salt + Hydrogen gas
How do bases react with metals.
2NaOH(aq) + Zn(s) → Na2ZnO2 (s) + H2 (g)
When bases react with metals you find that hydrogen is formed in the reaction. However, such reactions are not possible with all metals.
How do metal carbonates and metal bicarbonates react with acids and bases?
Test Tube A: Na2CO3 + 2HCl → 2NaCl + H2O +CO2
Test Tube B: NaHCO3 + HCl → NaCl + H2O +CO2
Therefore, the reaction between metal carbonates/bicarbonates and acids produce a salt, carbon dioxide and water.
What are the different forms of calcium carbonate?
Limestone chalk and arble are different forms of calcium carbonate.
How do Acids and Bases react with each other?
NaOH + HCl → NaCl + H2O
In the above reaction, teh effect of the base is nulified by an acid and vice-versa. The reaction betwee nan acid and a base to give a salt and water is known as a neutralisation rectaion.
Acid + Base → Salt + Water
How do metallic oxides react with acids?
CuO + 2HCl → CuCl2 +H2O
In the above reaction, you will notice that the colour of the solution becomes blue-green and the copper oxide dissolves. The blue-green colour of the solution is due to the formation of copper (II) chloride. The general reaction between a metal oxide and an acid can be written as -
Metal oxide + Acid → Salt + Water
What happens when CO2 is passeed through lime water?
On passing CO2 through evolved lime water:
Ca(OH)2 + CO2 → CaCO3 + H2O
CaCO3 is a white precipitate and the solution becomes milky. Wen excess CO2 is passed:
CaCO3 + H2O + CO2 → Ca(HCO3)2
Describe the recation between non-metallic oxides and bases.
Calcium hydroxide, which is a base, reacts
with carbon dioxide to produce a salt and water. Since this is similar to
the reaction between a base and an acid, we can conclude that nonmetallic oxides are acidic in nature.
Why do glucose and alcohol not conduct electricity?
Glucose and alcohol solutions do not conduct
electricity. The electric current is carried through the acidic solution by ions. Acids contain H+ ion as cation and anion such as Cl– in HCl, NO3– in HNO3, SO2– 4
in H2SO4, CH3COO– in CH3COOH. Since the cation present in acids is H+, this suggests that acids produce hydrogen ions, H+ (aq), in solution, which are responsible for their acidic properties. Since glucose and alcohol don’t produce ions they don’t conduct electricity.
What happens when acids in the presence of water?
Hydrogen ions in HCl are produced in the presence of water. The separation of H+ ion from HCl moleculescannot occur in the absence of water. HCl + H2O → H3O+ + Cl–
Hydrogen ions cannot exist alone, but they exist after combining with water molecules. Thus hydrogen ions must always be shown as H+ (aq) or hydronium ion (H3O+).
H+ + H2O → H3O+
We have seen that acids give H3O+ or H+ ion in water.
What happens when a base is dissolved in water?
NaOH (H2O)→ Na+ + OH-
Bases generate hydroxide (OH-) ions in water. Bases which are soluble in water are called alkalis.
