Class 7 Science Chapter 4 MCQ

Lemon water is acidic in nature. Acids do not turn all indicators red e.g. china rose indicator turns to dark pink (magenta) when acidic compound is added to it. Common salt and water both are neutral. Hence, have no effect on litmus.

Making solution of acid and water evolve heat. Acid should be added to water dropwise.

Phenolphthalein is a synthetic (man-made) indicator.

Here, all the statements are correct. Hence, your answer should be option [D].

Red litmus gives red colour in lemon juice which cannot be seen because red color mix with red litmus paper. Rest of all options are correct. Hence, your answer will be option [D].

Here, all the statements are correct. Hence, your answer will be option [D].

The soil may be acidic or basic naturally. The excessive use of fertilizers in the fields also makes the soil too acidic. When the soil is too acidic, it is treated with base such as quicklime (calcium oxide) or slaked lime (calcium hydroxide) which neutralize the excess acid present in the soil and reduces its acidic nature. In the soil is too basic, then decaying organic matter (called manure or compost) is added it. The decaying organic matter releases acid which neutralize the excess bases present in the soil and reduces its basic nature. Hence, your answer will be option [D].

Here all the statements are correct. Hence, your answer will be option [D].

Here all the statements are correct. Hence, your answer will be option [D].

Here all the statements are correct. Hence, your answer will be option [D].

Tooth decay is caused by the presence of an “acid”. Sodium Hydroxide turns red litmus blue. Here only option [B] is correct. Hence, your answer will be option [B].

As an example, to understand: methyl orange and phenolphthalein used as indicator. In acidic solution, methyl orange gives red colour but in basic solution it gives yellow colour. In acidic solution, phenolphthalein is colourless but in basic it gives pink colour. Thus, the change of colour in acid and a base depends on the type of indicators.

Basic solution changes the turmeric indicator from yellow to red.

When litmus is added to a basic solution it turns “blue”. Rest of all statements are correct. Hence, your answer will be option [D].

Bases turn china rose indicator to “green”. Rest of all statements are correct. Hence, your answer will be option [C].

Curd contains lactic acid and vinegar contains acetic acid. Lime water, soap and milk of magnesia are basic substances and grapes contain tartaric acid.

Here all the statements are correct. Hence, your answer will be option [D].

Phenolphthalein is colourless in acidic and neutral medium but turns pink when introduced in basic medium.

Hydrochloric acid, sulphuric acid and nitric acid are strong acids. On the other hand, acetic acid, formic acid, citric acid, tartaric acid and carbonic acid are some examples of the “weak acid”. Rest of all statements are correct. Hence, your answer will be option [D].

Ammonium hydroxide or ammonia solution is found in window cleaners. Rest of all statements are correct. Hence, your answer will be option [D].

Sodium hydroxide and potassium hydroxide are dangerous bases which can burn our skin. They must be handled very carefully.

Turmeric paste changes its colour from yellow to red when treated with a base. So, turmeric is an acid base indicator.

Red litmus gives red colour in lemon juice which cannot be seen because red color mix with red litmus paper. Rest of all options are correct. Hence, your answer will be option [D].

Acid and base participate in neutralization reaction and produce salt and water.

Antacids are a group of mild bases which have “no” toxic effects on the body. Rest of all statements are correct. Hence, your answer will be option [B].