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.

Instead of these she should take, an antacid (milk of magnesia) which is a base and neutralize the acidity. Milk of magnesia contains a base magnesium hydroxide which reacts with the acids and cures indigestion.

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

Phenolphthalein remains colour-less in acidic solution but turns pink in basic solution.

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].

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

Litmus is a mauve (purple) colour pigment obtained from Lichens. It turns red when added to acidic solution and blue when added to a basic solution.

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.

Phenolphthalein indicator is synthetic (man-made), acid-base indicator. Rest of all statements are correct. Hence, your answer will be option [A].

Citric acid is present in citrus fruits such as lemon and oranges. And tartaric acid is present in tamarind.

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

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].

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.

Calcium Hydroxide, ammonium hydroxide and sodium carbonate are weak base but their solution are unsafe to drink. Magnesium hydroxide is a very weak base which is safe to drink. It is used in milk of magnesia and other indigestion mixtures.

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.