Page 1 : HOTS QUESTIONS, Question 1: If you get a turmeric (haldi) stain on your clothes while eating food, and try to wash it off with, soap, the stain becomes red. Why? Find out how to remove haldi stains from clothes., , ANSWER: Turmeric is a natural acid-base indicator. It turns red in a basic solution and pale yellow in an, acidic solution., , Therefore, the turmeric stain will turn red after coming in contact with the soap, indicating the basic nature of, the soap (generally soaps are bases — containing sodium hydroxide)., , Turmeric contains a type of yellow pigment which is responsible for the staining the clothes., , These stains can be removed using the following methods:, 1. Fresh stains can be removed easily by immediately washing them with a soap. However, if there is a delay, in washing, the stains will be hard to remove in a single wash. In this case, the stains need to be washed, repeatedly using a soap., , 2. By applying lemon juice or vinegar on these stains along with a dish soap can help remove the turmeric, stains in a better way., , 3. By soaking the stained part in the soda water (baking soda + water) for half an hour, will help in removing, the turmeric stains easily., , , , Question 2: Is the meaning of ‘weak acid’ the same as that of ‘dilute acid’?, , ANSWER: Weak acids are completely different from dilute acids. Weak acids are non-corrosive in nature, even in their highly concentrated state. Generally, all organic acids like citric acid, lactic acid, oxalic acid,, etc., are weak acids. However, dilute acids are also non-corrosive in nature but are formed by mixing, concentrated acids with a large amount of water. For example, dilute hydrochloric acid, dilute sulphuric acid,, etc. Dilute acids can include both strong and weak acids., , Question 3: The wastes of many factories contain acids. Why is it considered necessary to neutralize them, before allowing the wastes to flow into water bodies?, , ANSWER: Acids are extremely corrosive in nature; therefore, they can cause extensive damage to the living, organisms present in water. Also, if the wastes are allowed to flow into the water bodies without treatment,, they can pollute the water, making it unfit for drinking. Hence, the wastes should be neutralised by bases, , before releasing them into water bodies. The base calcium hydroxide (Ca(OH)2) is widely used to treat wastes,, containing acids, from the industries.