Chapter 5- Acids, Bases and Salts-Class 7 Question and Answer (MCQ)

Question- What is derived from the Latin word “acere”?

a) Bases

b) Acids

c) Baking soda

Answer- b) Acids
Explanation- The term “acid” is derived from the Latin word “acidus” or “acere” which means sour, referring to the sour taste characteristic of acids.

Question- Which acid is produced by ants as a defence mechanism?

a) Citric Acid

b) Formic Acid

c) Lactic Acid

Answer- b) Formic Acid
Explanation- Ants produce formic acid as a defence mechanism. When ants bite or sting, they inject formic acid into the skin, causing pain and irritation.

Question- Which base is found in “Milk of Magnesia”?

a) Sodium Bicarbonate

b) Magnesium Hydroxide

c) Potassium Hydroxide

Answer- b) Magnesium Hydroxide
Explanation- “Milk of Magnesia” contains magnesium hydroxide, a base that is used as an antacid to neutralise stomach acids and relieve indigestion and heartburn.

Question- Which of the following is a characteristic of bases?

a) Sour taste

b) Soapy feel

c) Change colour in presence of indicator

Answer- b) Soapy feel
Explanation- Bases feel soapy or slippery to touch. This is a physical property commonly used to identify them.

Question- Which indicator is derived from a flower?

a) Litmus

b) Turmeric

c) China rose petals (Gudhal)

Answer- c) China rose petals (Gudhal)
Explanation- China rose petals (Gudhal) are used to make an indicator which changes colour in the presence of acids and bases, helping in their identification.

Question- Which acid is found in an ant’s sting?

a) Citric Acid

b) Formic Acid

c) Lactic Acid

Answer- b) Formic Acid
Explanation- Ants use formic acid in their stings as a defence mechanism, causing pain and irritation to deter predators.

Answer- b) Giving a tangy flavour
Explanation– Lactic acid formed during the fermentation process gives curd (yoghurt) its characteristic tangy flavour.

Question- In which substance is tartaric acid commonly found?

a) Lemon

b) Tamarind

c) Vinegar

Answer- b) Tamarind
Explanation- Tartaric acid is present in tamarind, contributing to its sour taste and is commonly used as a food ingredient.

Question- What is a common application of ammonium hydroxide?

a) Food preparation

b) Cleaning

c) Water treatment

Answer- b) Cleaning
Explanation- Ammonium hydroxide, also known as ammonia water, is commonly used as a cleaning agent because it is effective in removing stains and dirt from surfaces.

Question- Which base is found in milk of magnesia?

a) Sodium Hydroxide

b) Magnesium Hydroxide

c) Calcium Hydroxide

Answer- b) Magnesium Hydroxide
Explanation- Milk of magnesia contains magnesium hydroxide, which acts as an antacid and a laxative.

Question- What is the use of calcium hydroxide in lime water?

a) Cleaning

b) Water treatment and food preparation

c) Manufacture of soap

Answer- b) Water treatment and food preparation
Explanation- Calcium hydroxide is present in lime water and is used for treating water and in food preparation, such as in making pickles.

Question- Which colour does red litmus paper turn into a basic solution?

a) Red

b) Blue

c) Mauve

Answer- b) Blue
Explanation- Red litmus paper turns blue in a basic solution, indicating the presence of a base.

Question- What does a neutral solution do to litmus paper?

a) Turns it red

b) Turns it blue

c) No colour change

Answer- c) No colour change
Explanation- A neutral solution does not affect the colour of litmus paper, as it is neither acidic nor basic.

Question- Where is litmus extracted from?

a) Flowers

b) Lichens

c) Fruits

Answer- b) Lichens
Explanation- Litmus is a natural dye extracted from lichens, used as an indicator in acid-base reactions.

Question- What colour does turmeric paper turn when exposed to a basic solution?

a) Yellow

b) Red or brownish-red

c) No change

Answer- b) Red or brownish-red
Explanation- Turmeric paper turns red or brownish-red in the presence of a basic solution due to a chemical reaction that occurs between the turmeric and the base, altering the natural yellow colour of turmeric.

Question- What is the primary reaction of turmeric as a natural indicator?

a) Reacts with acids

b) Reacts with bases

c) Reacts with neutrals

Answer- b) Reacts with bases
Explanation- Turmeric primarily reacts with bases, changing colour as a result of this interaction, making it a good indicator for identifying basic substances.

Question- Which substance does not change the colour of turmeric paper?

a) Lemon Juice

b) Baking Soda

c) Lime Water

Answer- a) Lemon Juice
Explanation- Lemon juice is acidic and turmeric paper is mainly responsive to bases; hence, it doesn’t change colour when exposed to lemon juice.

Question- What is the colour change observed in a basic solution when tested with the China Rose indicator?

a) Magenta

b) Green

c) No change

Answer- b) Green
Explanation- China Rose indicator turns green when added to a basic solution due to the chemical reaction that occurs between the indicator and the base.

Question- What material is primarily used to prepare the China Rose indicator?

a) China rose petals

b) Turmeric powder

c) Litmus

Answer- a) China rose petals
Explanation- China Rose indicator is made primarily from the petals of the China rose flower, utilised for their colour-changing properties in the presence of acids and bases.

Question- Which solution is likely to not show a significant colour change when tested with the China Rose indicator?

a) Vinegar

b) Sugar Solution

c) Lemon Juice

Answer- b) Sugar Solution
Explanation- A sugar solution is neutral and doesn’t cause a significant colour change in the China Rose indicator, as it reacts mainly with acids and bases.

Question- What colour does litmus paper turn in the presence of dilute hydrochloric acid?

a) Blue

b) Red

c) Green

Answer- b) Red
Explanation- Litmus paper turns red in the presence of an acid, like dilute hydrochloric acid, due to the hydrogen ions reacting with the litmus dye.

Question- Which substance turns turmeric paper red?

a) Dilute Sulphuric Acid

b) Sodium Hydroxide

c) Dilute Acetic Acid

Answer- b) Sodium Hydroxide
Explanation– Sodium Hydroxide is a base, and bases cause turmeric paper to turn red, a reaction indicative of their basic nature.

Question- What effect does China Rose solution show when added to calcium hydroxide?

a) No Change

b) Turns Green

c) Turns Dark Pink/Magenta

Answer- b) Turns Green
Explanation- China Rose solution reacts with bases, like calcium hydroxide, turning green, which is a characteristic reaction of this natural indicator.

Question- What is formed when an acid reacts with a base in a neutralisation reaction?

a) Water and Gas

b) Water and Salt

c) Salt and Gas

Answer- b) Water and Salt
Explanation- In a neutralisation reaction between an acid and a base, water and salt are produced as products.

Question- What colour does phenolphthalein turn into a basic solution?

a) Colourless

b) Blue

c) Pink

Answer- c) Pink
Explanation- Phenolphthalein is a pH indicator that turns pink in basic solutions due to changes in its molecular structure that alter its absorption spectrum.

Question- What should one always remember when handling acids and bases?

a) Store them openly

b) Exercise caution to prevent harm or injury

c) They are not harmful

Answer- b) Exercise caution to prevent harm or injury
Explanation- Acids and bases can be corrosive and harmful, and handling them requires care and proper safety measures to prevent any injuries or accidents.

Question- What is always produced in a neutralisation reaction?

a) Salt only

b) Water only

c) Salt and water

Answer- c) Salt and water
Explanation- In a neutralisation reaction, an acid reacts with a base to always produce salt and water, demonstrating the neutralising effect they have on each other.

Question- Which of the following will be warm during a neutralisation reaction?

a) Reactants

b) Products

c) Container

Answer- c) Container
Explanation- The container gets warm during a neutralisation reaction due to the exothermic nature of the reaction, where heat is released.

Question- What is the nature of salts produced in a neutralisation reaction?

a) Always Neutral

b) Always Basic

c) Can be acidic, basic, or neutral

Answer- c) Can be acidic, basic, or neutral
Explanation- The nature of salts produced in a neutralisation reaction can vary; they can be acidic, basic, or neutral depending on the strength and characteristics of the reacting acid and base.

Question- What is used to neutralise the effect of an ant bite?

a) Vinegar

b) Baking soda

c) Salt

Answer- b) Baking soda
Explanation- Baking soda, being a base, helps to neutralise the acidic venom injected by the ant during a bite.

Question- What happens during the neutralisation of stomach acids in case of indigestion?

a) Acid is increased

b) Acidity remains the same

c) Acidity is reduced

Answer- c) Acidity is reduced
Explanation- Antacids neutralise stomach acids, thereby reducing acidity and alleviating indigestion symptoms.

Question- Which of the following scenarios involves neutralisation in everyday life?

a) Charging a battery

b) Digesting food

c) Soil treatment in agriculture

Answer- c) Soil treatment in agriculture
Explanation- Neutralisation is used in agriculture to manage soil acidity or alkalinity levels, ensuring optimal conditions for plant growth.

Also Check – Class 7- Chapter 4 – Acids, Bases and Salts – 4 Worksheets Solved and Unsolved

Also Check – NCERT Exemplar Solutions- Class 7 Science Chapter – 5- Acids, Bases and Salts