NCERT Class VII Science Solutions: Chapter 5-Acids, Bases and Salts Part 2

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Question 8:

A solution changes the colour of turmeric indicator from yellow to red. The solution is

  1. Basic

  2. Acidic

  3. Neutral

  4. Either neutral or acidic

Answer: A

Image of turmeric reaction

Image of Turmeric Reaction

Image of turmeric reaction

Question 9:

Which of the following set of substances contain acids?

  1. Grapes, lime water

  2. Vinegar, soap

  3. Curd, milk of magnesia

  4. Curd, vinegar

Answer: D

Question 10:

On adding phenolphthalein indicator to a colourless solution, no change is observed. What is the nature of this solution?

  1. Basic

  2. Either acidic or basic

  3. Either acidic or neutral

  4. Either basic or neutral

Answer: C

Image of Phenolphthalein color change

Image of Phenolphthalein Color Change

Image of Phenolphthalein color change

Question 11:

Which of the following is an acid-base indicator?

  1. Vinegar

  2. Lime water

  3. Turmeric

  4. Baking soda

Answer: C

VERY SHORT ANSWER QUESTIONS

Question 12:

Look at the given reaction.

Sodium chloride formed in this reaction remains in solution form. Can we get solid sodium chloride from this solution? Suggest a method (if any).

Answer:

We can get solid sodium chloride by evaporation method. Water changes to vapour form during evaporation and solid sodium chloride is left in the container.

Image of Reaction between Hydrochloric acid and sodium hydroxide

Reaction of Hydrochloric Acid with Sodium Hydroxide

Image of Reaction between Hydrochloric acid and sodium hydroxide

Question 13:

State whether the following statements are true or false.

Correct the false statements.

  1. All substances are either acidic or basic.

  2. A compound if acidic will turn all indicators red.

  3. Lime water turns red litmus blue.

  4. Common salt dissolved in water turns blue litmus red.

  5. Phenolphthalein is a natural indicator.

  6. Calamine can be used to treat ant’s sting.

  7. Lemon water is basic in nature.

Answer:

  1. False. Substances can be neutral as well.

  2. False. Acids do not turn all indicators red.

  3. True

  4. False. It does not change the colour of litmus at all.

  5. False. It is a man-made indicator.

  6. True

  7. False. It is acidic in nature.