Acids, Bases and Salts Overview

If someone in the family is suffering from a problem of acidity after overeating, which of the following would you suggest as a remedy: lemon juice, vinegar or baking soda solution?

Which property did you think of while choosing the remedy?

You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?

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.

Which of these - vanilla, onion, and clove - can be used as olfactory indicators?

What do you observe on the surface of zinc granules when added to dilute sulphuric acid?

Why are bubbles formed in the soap solution when the gas is passed through it?

What do you observe when a burning candle is taken near the gas-filled bubble?

The reaction of a metal with an acid can be summarized as Acid + Metal → Salt + Hydrogen gas

Write the equations for reactions you have observed with zinc in dilute sulphuric acid, and zinc in sodium hydroxide.

Such reactions (of metal and acid) are not possible with all metals.

What do you observe when you add dilute HCl to sodium carbonate and sodium hydrogencarbonate?

Write the chemical equations for both reactions.

What do you observe when you pass the gas evolved in each case through lime water?

The reaction between an acid and a base to give a salt and water is known as a neutralisation reaction.

Write a general equation for a neutralisation reaction.

What happens when a small amount of copper oxide is added to dilute hydrochloric acid?

Write a general equation for the reaction between a metal oxide and an acid.

Why should curd and sour substances not be kept in brass and copper vessels?

Which gas is usually liberated when an acid reacts with a metal?

Illustrate with an example. How will you test for the presence of this gas?

Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.

All compounds containing hydrogen are acidic.

What happens when solutions of glucose, alcohol, hydrochloric acid, sulphuric acid, etc. are tested with a 6-volt battery using a bulb and switch?

Acids produce hydrogen ions, H+(aq), in solution which are responsible for their acidic properties.

Acids produce ions only in aqueous solution.

The effect of a base is nullified by an acid and vice versa.

Bases generate hydroxide (OH-) ions in water.

All bases dissolve in water.

What happens when water is mixed with an acid or a base?

The strength of acids and bases depends on the number of H+ ions and OH- ions produced, respectively.

Our body works within the pH range of 7.0 to 7.8.

Living organisms can survive only in a narrow range of pH change.

Rain water with pH less than 5.6 is called acid rain.

The pH of the soil in your backyard affects the healthy growth of plants.

Our stomach produces hydrochloric acid.

Tooth decay starts when the pH of the mouth is lower than 5.5.

Nettle stings cause pain and irritation. Use of a mild base like baking soda on the stung area gives relief.

The common salt (NaCl) obtained is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda, bleaching powder and many more.

When electricity is passed through an aqueous solution of sodium chloride (called brine), it decomposes to form sodium hydroxide. The process is called the chlor-alkali process because of the products formed - chlor for chlorine and alkali for sodium hydroxide.

Bleaching powder is used for bleaching cotton and linen in the textile industry, for bleaching wood pulp in paper factories and for bleaching washed clothes in laundry.

Baking soda is commonly used in the kitchen for making tasty crispy pakoras, etc. Sometimes it is added for faster cooking.

Washing soda can be obtained by heating baking soda, recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.

When water is added to Plaster of Paris, it changes into gypsum, releasing heat - an exothermic process.

What is the common name of the compound CaOCl₂?

Name the substance which on treatment with chlorine yields bleaching powder.

Name the sodium compound which is used for softening hard water.

What will happen if a solution of sodium hydrogencarbonate is heated?

Give the equation of the reaction involved.

Write an equation to show the reaction between Plaster of Paris and water.