Class 7 . Acids bases and salts

An oxide is acidic and has a pungent odour. It could be

• sulphur dioxide

• carbon dioxide

• sodium oxide

• nitrogen dioxide

Out of these gases which one is used in fire extinguishers

• CO2

• SO2

• NO2

• H2S

The correct way of making a solution of acid in water is to

• add water to acid

• add acid to water

• mix acid and water simultaneously

• add water to acid in a shallow container

Products of a neutralisation reaction are always:

• acid and a base

• acid and a salt

• salt and water

• salt and a base

Turmeric is a natural indicator. On adding its paste to acid and base separately, which colours would be observed.

• Yellow in both acid and base

• Yellow in acid and red in base

• Pink in acid and yellow in base

• Red in acid and blue in base

Phenolphthalein is a synthetic indicator and its colours in acidic and basic solutions, respectively are:

• red and blue

• blue and red

• pink and colourless

• colourless and pink

When the soil is too basic, plants do not grow well in it. To improve its quality what must be added to the soil?

• Organic matter

• Quick lime

• Slaked lime

• Calamine solution

Which of the following set of substances contain acids?

• Grapes, lime water

• Vinegar, soap

• Curd, milk of magnesia

• Curd, vinegar

A change is a chemical change when it is accompanied by:

• energy change

• formation of new substances

• change in chemical properties

• all of the above

Expansion and contraction of metals is a:

• physical change

• chemical change

• irreversible change

• none of these