While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?

NCERT Solutions for Class 10 Science Chapter 2 Acids, Bases, and Salts: Students must know that NCERT Acids Bases and Salts Class 10 Science chapter 2 solutions is an important chapter from which 3 marks or 5 marks questions may be asked. In these NCERT solutions for Acids Bases and Salts Class 10 Science chapter 2, you will come to know the answers and step wise solutions to the questions asked in Q 1. Answer: Litmus is a common indicator that is used to identify acid and base. The colour of litmus paper turns to blue indicates that the chemical is a base. If there is no change in colour, then the chemical is either acidic or neutral. First marks the three test tubes as A, B, and C. Now, (i) First of all, put the red litmus paper in each test tube one by one. The test tube in which red litmus paper will turn blue indicates the solution of that test tube is basic/Alkaline in nature. (ii) Now remaining two are either acidic or neutral. Now mix a drop of the basic solution with a drop of each of the remaining two solutions separately and then the nature of the drops of the mixtures is checked. If the colour of the red litmus turns blue, then the second solution is neutral and if there is no change in colour, then the second solution is acidic. This is because acidic and basic solutions neutralize each other. NCERT solutions for class 10 science chapter 2 Acids, Bases and Salts Topic 2.1 - Understanding the chemical properties of acids and bases Q.1 Answer: Curd and sour subs...

Q 1. 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 tubes? SOLUTION: Take three small pieces of red litmus paper. Put one drop each of the given solutions on these litmus papers. The liquid which turns red litmus into blue is a basic solution. Divide the blue litmus paper so formed into two parts. Put one drop each of the other two liquids separately on these two pieces of litmus paper. The solution which turns blue litmus paper red is acidic solution. The solution which does not affect the colour of litmus paper is water. Q 2. Why should curd and sour substances not be kept in brass and copper vessels? SOLUTION: The curd and sour substances are acidic. They will react with brass (alloy of copper and zinc metals) and copper vessels and will spoil the vessels. Q 3. 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? SOLUTION: Hydrogen gas is liberated when an acid reacts with a metal. For example, when zinc metal reacts with dil.HCl, hydrogen is evolved and salt zinc chloride is formed as: Zn ( s) + 2HCl (aq) → ZnCl 2(aq) + H 2( g) It can be tested by bringing a burning candle near the gas. The candle continues burning with a pop sound. Q 4. A metal compound A reacts with dilute hydroc...

When a concentrated acid is added to water for preparing a dilute acid, then the heat is evolved gradually and easily absorbed by the large amount of water (to which the acid is being added) however if water is added to concentrated acid, then large amount of heat is evolved at once. This heat changes some of the water to steam explosively which can splash the acid on our face or clothes and causeacid burns. Even the glass container may break due to the excessive heating.

While diluting an acid, the acid should always be added slowly to water with constant stirring and in small amounts. The dilution of an acid is an exothermic reaction. So, when we add acid to water, the evolvedheat gets absorbed by the water that is in bulk. But when we add water to acid, a large amount of heat is evolved, the water turns into vapour and the acid splashes onto our clothes or face, causing severe burns.