Acid, Bases and Salts

• Carbohydrates are the most abundant organic compounds on earth.
• The sour and bitter tastes of food are due to acids and bases, respectively, present in them.
• Lemon juice, vinegar and baking soda solution are suggested as remedies for acidity after overeating.
• Acids are sour in taste and change the colour of blue litmus to red, whereas, bases are bitter and change the colour of the red litmus to blue.
• You will notice discharge coming out of the nozzle.
• Direct this discharge on a burning candle.
• Tilt the wash-bottle so that the acid from the ignition tube mixes with the sodium hydrogencarbonate solution below.
• 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.
• The effect of a base is nullified by an acid and vice-versa.
• Metallic oxides react with acids to give salts and water, similar to the reaction of a base with an acid, metallic oxides are said to be basic oxides.
• Curd and sour substances should not be kept in brass and copper vessels due to their acidic nature.
• Metal carbonates and metal hydrogencarbonates react with acids to give a corresponding salt, carbon dioxide and water.
• Non-metallic oxides are acidic in nature.
• When an acid reacts with a metal, carbon dioxide gas is usually liberated.
• The reaction between an acid and a base to give a salt and water is known as a neutralisation reaction.
• There are many other natural materials like red cabbage leaves, turmeric, coloured petals of some flowers such as Hydrangea, Petunia and Geranium, which indicate the presence of acid or base in a solution.
• These indicators are called acid-base indicators or sometimes simply indicators.
• Acids and bases cancel out each other’s effects.
• Acids are changed to bases and bases are changed to acids when they react with each other.
• Acids and bases react with each other in a specific way.
• Acids change the colour of blue litmus to red and change the colour of red litmus to blue.
• Bases change the colour of blue litmus to blue and change the colour of red litmus to red.
• Litmus is a natural indicator, turmeric is another such indicator.
• Acids react with metals to form a salt and hydrogen gas.
• Such reactions are not possible with all metals.
• Onion, clove, and vanilla can be used as olfactory indicators based on their odour.
• The reactions occurring in the above Activity are written as Na CO HCl(aq) Cl(aq) H O(l) + CO 2 3 2 2 (s) Na (g) + → + 2 2.
• Phenolphthalein and litmus are used as indicators in acid-base titrations.
• The reaction of a metal with an acid can be summarised as Acid + Metal → Salt + Hydrogen gas.
• The reaction that takes place when zinc metal is added to sodium hydroxide solution can be written as 2NaOH(aq) + Zn(s) → Na 2 ZnO 2 (s) + H 2 (g) (Sodium zincate)
• Red litmus solution is used to test for acids, while blue litmus solution is used to test for bases.
• Hydrogen is formed in the reaction of zinc metal with sodium hydroxide solution.
• Phenolphthalein is used to test for alkaline solutions.
• On passing the carbon dioxide gas evolved through lime water, Ca(OH) CO H O (l) 2 2 2 (aq) (g) CaCO s 3 + → + ( ) (Lime water) (White precipitate)
• A stain of curry on a white cloth becomes reddish-brown when soap, which is basic in nature, is scrubbed on it.
• Synthetic indicators such as methyl orange and phenolphthalein can also be used to test for acids and bases.
• Baking soda, also known as sodium hydrogencarbonate (NaHCO 3 ), is commonly used in the kitchen for making tasty crispy pakoras, etc.
• Sodium hydrogencarbonate is a mild non-corrosive basic salt and can be used to neutralise an acid.
• Sodium carbonate (washing soda) is used in glass, soap and paper industries.