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A farmer was unhappy because of his low crop yield. He discussed the problem with an agricultural scientist and realised that the soil of his field was either too acidic or too basic. What remedy would you suggest the farmer to neutralise the soil?

Answer: Bases such as quick lime (calcium oxide) or slaked lime (calcium hydroxide) are used to treat soils that are highly acidic. Organic... View Article

Boojho, Paheli and their friend Golu were provided with a test tube each containing China rose solution which was pink in colour. Boojho added two drops of solution ‘A’ in his test tube and got a dark pink colour. Paheli added 2 drops of solution ‘B’ to her test tube and got green colour. Golu added 2 drops of solution ‘C’ but could not get any change in colour. Suggest the possible cause for the variation in their results.

Answer: Since solution A turns China rose colour to dark pink hence Solution A is an acidic solution. solution B turns China rose colour to green... View Article

When an acidic solution is mixed with a basic solution, they _ each other forming _ and water.

Answer: When an acidic solution is mixed with a basic solution, they neutralize each other forming salt and water. An acid is any... View Article

Phenolphthalein gives _________ colour with lime water.

Answer: Phenolphthalein gives pink colour with lime water. Phenolphthalein is naturally colourless but turns pink in alkaline solutions. In... View Article

Turmeric and litmus are _________ acid-base indicators.

Answer: Turmeric and litmus are natural acid-base indicators. Indicators are chemical compounds that tell us whether a substance is acidic or... View Article

Lemon juice and vinegar taste _ because they contain _.

Answer: Lemon juice and vinegar taste sour because they contain acids. Acids are chemical substances that are characterized by a sour taste in... View Article

Match the substances in Column I with those in Column II.

Column I Column II a) Tartaric acid i) Soap b) Calcium hydroxide ii) Curd c) Formic acid iii) Unripe mangoes d) Sodium Hydroxide iv)... View Article

Form a sentence using the following words – baking soda, ant bite, moist, effect, neutralised, rubbing.

Answer: The effect of an ant bite can be neutralised by rubbing moist baking soda. The acid which ants produce is called methanoic acid or... View Article

While playing in a park, a child was stung by a wasp. Some elders suggested applying the paste of baking soda and other lemon juice as the remedy. Which remedy do you think is appropriate and why?

Answer: Baking soda is a better remedy than lemon juice. When a wasp stings, methanoic acid is released into the sting region, causing... View Article

Look at Figure which shows solutions taken in test tubes A, B, C and D. What colour is expected when a piece of red litmus paper is dropped in each test tube? Nature of the solutions is given in the table for your help.

Answer: Litmus paper is a type of paper that changes colour in response to the acidity of the solution it is dipped in and can thus be used to... View Article

Paheli is suffering from indigestion due to acidity. Is it advisable to give her orange juice in this situation and why?

Answer: The acidity in orange juice is high. As a result, she should avoid drinking orange juice in her current situation because it increases... View Article

State whether the following statements are true or false. Correct the false statements. (a) All substances are either acidic or basic. (b) A compound if acidic will turn all indicators red. (c) Lime water turns red litmus blue. (d) Common salt dissolved in water turns blue litmus red. (e) Phenolphthalein is a natural indicator. (f) Calamine can be used to treat ant’s sting. (g) Lemon water is basic in nature.

Answer: (a) False- Substance can be acidic, basic or neutral in nature (b) False- Acids do not turn all indicators red. (c) True (d) False-... View Article

Look at the given reaction. Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any).

Answer: Hydrochloric acid + Sodium hydroxide (base) → Sodium chloride (salt) + Water Sodium chloride is soluble in water and forms a sodium... View Article

Which of the following is an acid-base indicator? (a) Vinegar (b) Lime water (c) Turmeric (d) Baking soda

Answer: (c) Turmeric Turmeric will be yellow in acidic solution and red in basic solution. Turmeric compound is a naturally occurring yellow... View Article

On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution? (a) Basic (b) Either acidic or basic (c) Either acidic or neutral (d) Either basic or neutral

Answer: (c) Either acidic or neutral Colour of phenolphthalein indicator will not change with an acidic or neutral solution. One popular... View Article

Which of the following set of substances contain acids? (a) Grapes, lime water (b) Vinegar, soap (c) Curd, milk of magnesia (d) Curd, vinegar

Answer: (d) Curd, vinegar Curd contains lactic acid and vinegar contains acetic acid. The curd is produced due to the presence of reaction... View Article

A solution changes the colour of turmeric indicator from yellow to red. The solution is (a) basic (b) acidic (c) neutral (d) either neutral or acidic

Answer: (a) basic Turmeric is acidic in nature hence it is converted to red due to neutralization by the base. Turmeric compound is a naturally... View Article

A neutralisation reaction is a (a) physical and reversible change. (b) a physical change that cannot be reversed. (c) chemical and reversible change. (d) the chemical change that cannot be reversed.

Answer: (d) the chemical change that cannot be reversed. It is a chemical reaction where acid and base reacts with each other quantitatively.... View Article

‘Litmus’, a natural dye is an extract of which of the following? (a) China rose (Gudhal) (b) Beetroot (c) Lichen (d) Blueberries (Jamun)

Answer: (c) Lichen Litmus solution is a purple dye, which is extracted from Lichen, a plant belonging to division Thallophyta and is commonly... View Article

When the soil is too basic, plants do not grow well in it. To improve its quality what must be added to the soil? (a) Organic matter (b) Quick lime (c) Slaked lime (d) Calamine solution

Answer: (a) Organic matter Organic matter is added to basic soil to neutralize its base which improves its quality. Organic substance is found... View Article

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