Acids Bases and Salts Test - 19

Litmus paper is an indicator which gives us information about acidic and basic solutions by changing its colour. Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions.

Since HCl and orange juice are acidic so they turn blue litmus paper into red.

NaCl is salt of strong acid and strong base so they will have no effect on the litmus paper. 

NaOH is the base so it turns red litmus paper into red. 

Hence option (B) is correct. 

This activity uses turmeric, a common spice in curry, as an indicator of acidity and basicity. Turmeric is yellow in acid and neutral substances but turns bright red with bases.

Since salts are neutral in nature so they will not form any colour with the turmeric solution. 

Hence, option (B) is correct.

Calcium oxide, commonly known as quicklime or burnt lime, is a widely used chemical compound. It is a white, caustic, alkaline, crystalline solid at room temperature.

Hence option (D) is correct. 

Turmeric is an acid-base indicator that is yellow in acidic and neutral solutions and orange or reddish-brown in basic solutions

Turmeric is slightly bitter in taste. 

Hence we can complete the sentence by filling base and bitter respectively.

Hence, option (A) is correct.

Turmeric is an acid-base indicator that is yellow in acidic and neutral solutions and orange or reddish-brown in basic solutions.

Soap solution is a basic solution which changes into reddish-brown colour in the presence of the turmeric solution. 

Hence, option (C) is correct.

As we know vinegar contains acetic acid, ant’s sting contains formic acid and tamarind contains tartaric acid. 

So it is clear that all are sharing common character in terms of having acidic nature. 

Hence option (C) is correct. 

(A) Lemon - Citric acid,

(B) Amla - Ascorbic acid,

(C) Spinach - Oxalic acid, 

(D) Ant’s sting - Formic acid.

Hence option (C) is correct. 

Milk of magnesia is an alkaline suspension as it consists of magnesium hydroxide, meaning that it will cause neutralization when it encounters anything acidic. This is why it makes an excellent antacid, as it neutralizes excess stomach acid (hydrochloric acid) when swallowed.

Hence, option (B) is correct.

To neutralise the basic nature of soil we must add acid into soil. 

Since slaked lime (Ca(OH)₂), quick lime (CaO) are basic in nature so cannot be added. 

Urea is neutral so it also will not help in the neutralization of basic soil. 

Organic acids are having weak acidic property so they can be added to the basic soil. 

Hence, option (A) is correct.

Acid rain is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. 

Since sulphuric acid contains SO₂ and nitric acid contains NO₂. Excess CO₂ may also be present in the acid rain which on reaction with water forms carbonic acid.

N₂O is not present in the acid rain.

Hence, option (D) is correct.

Litmus is a water-soluble mixture of different dyes extracted from lichens. 

Litmus paper acts as an indicator which provides information on acidic and basic nature of solutions. 

Litmus paper turns blue litmus paper into red colour in acidic solution and red litmus into blue in basic solution. 

Phenolphthalein and methyl orange are synthetic indicators which formed inside the laboratories. 

Lime is citrus fruit as it contains citric acid.

Hence option (B) is correct.

Indicators are those substances who change their colour in acidic as well as basic solution. 

China rose converts acidic solutions to dark pink, basic solutions to green colour and has no colour change for neutral solutions. China rose is a natural indicator and is used to identify the acidic or basic nature of a solution.

Turmeric remains yellow in acid and neutral substances, but turns bright red with bases.

Phenolphthalein is often used as an indicator in acid–base titrations. For this application, it turns colorless in acidic solutions and pink in basic solutions.

Blue litmus paper turns red under acidic conditions and red litmus paper turns blue under basic or alkaline conditions.

It is clear from the above explanation that only phenolphthalein and turmeric are the indicators who do not change their colours in acidic medium. 

Hence option (A) is correct. 

The sting of an ant contains formic acid. When an ant bites, it injects the acidic liquid into the skin. The effect of the sting can be neutralised by rubbing moist baking soda (sodium hydrogen carbonate) or calamine solution, which contains zinc carbonate.

Hence, option (D) is correct.

A neutralization reaction is when an acid and a base react to form water and a salt and involves the combination of H+ ions and OH- ions to generate water. Heat is released in this process so the temperature of the system will rise.

Hence option (C) is correct.

China rose converts acidic solutions to dark pink (magenta), basic solutions to green colour and has no colour change for neutral solutions.

Since blue litmus paper changes to red in acidic medium and red litmus paper to blue in basic medium. So this indicator cannot be used for the given transformation. 

Turmeric changes its colour only in the basic medium (bright red). It also can not be used for the given changes.

In the given question the solution turns its colour to magenta (dark pink colour) in presence of indicator. So from the given explanation it is clear that the indicator must be china rose in acidic solution. 

Hence option (B) is correct.