A solution turns red litmus blue, its pH is likely to be - Science


A solution turns red litmus blue, its pH is likely to be


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A basic solution turns red litmus blue. On the pH scale, bases have values greater than 7, whereas acids have values less than 7. Therefore, the pH of the given solution is likely to be 10.

Concept: Acids
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Chapter 2: Acids, Bases and Salts - Exercise 2 [Page 81]


Lakhmir Singh Class 10 Chemistry (Science)
Chapter 2 Acids, Bases and Salts
Exercise 2 | Q 44 | Page 81
NCERT Science Class 10
Chapter 2 Acids, Bases and Salts
Exercises | Q 1 | Page 34

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Name the source from which litmus solution is obtained. What is the use of this solution?

Mark ‘T’ if the statement is true and ‘F’ if it is false:

Sodium hydroxide turns blue litmus red. (T/F)

Mark ‘T’ if the statement is true and ‘F’ if it is false:

Tooth decay is caused by the presence of a base. (T/F)

Dorji has a few bottles of soft drink in his restaurant. But, unfortunately, these are not labelled. He has to serve the drinks on the demand of customers. One customer wants acidic drink, another wants basic and third one wants neutral drink. How will Dorji decide which drink is to be served to whom?

How will you test for the gas which is liberated when hydrochloric acid reacts with an active metal?


Give the names and formulae of two strong acids and two weak acids.

How will you test for the presence of this gas?

What colour does phenolphthalein indicator turn when added to an alkali (such as sodium hydroxide)?

A white shirt has a yellow stain of curry. When soap is rubbed on this shirt during washing, the yellow stain turns reddish-brown. On rinsing the shirt with plenty of water, the reddish-brown stain turns yellow again.

Name the natural indicator present in curry stain.

What happens to the H+ ions, of the solution, when an acid is neutralised?

Name the gas evolved when zinc granules are treated/heated with:

sodium hydroxide solution

What happens during a bee sting? What is its remedy?

Why is it wrong to treat a bee sting with vinegar?

Write any two important uses of bases.

Define the term ‘basicity’ of an acid.

Give two examples of the following:

Name an acid used to flavor and preserve food.

Give one example in the following case:
A weak mineral acid.

Give one example in the following case:
An oxide which is a base.

Distinguish between acidity of bases and basicity of acids.

Identify the following solutions, whether they are acid or base.

Solution Change in Indicator Acid/Base
Litmus Phenolphthalein Methyl orange
1. ______ No change ______ ______
2. ______ ______ The orange colour turns red ______
3. Red litmus turns blue ______ ______ ______

Write chemical names from given formulae.

H2SO4, Ca(OH)2, HCl, NaOH, KOH, NH4OH

Sulphuric acid has the highest importance in the chemical industry. Why?

Which acid is used for getting chloride salt?

By squeezing lemon on a piece of rock the gas liberated turned lime water milky. which compound is present in the rock?

The label on the bottle of chemical is spoiled. How will you find whether the chemical is acidic or not?

Which are the industrial uses of acids?

Tartaric acid is a................ acid.

Match the pairs. 

  Group A  Group B
1. Tamarind  a. Acetic acid
2. Curd  b. Citric acid
3. Lemon  c. Tartaric acid
4.Vinegar d. Lactic acid

State true or false

Table salt is acidic.

Define an acid.

Give the name and formula of two : Strong monobasic acids

Give the name and formula of two : Volatile acids

Define the following term: Acid.

Acids are ________ in taste.

In acidic solutions blue litmus changes into ______ colour.

The word sour refers to ______ in Latin.

Acids are bitter in taste.

Acids are corrosive in nature.

What are the uses of acids?

Vinu and Priyan take their lunch at school. Vinu eats lemon rice and Priyan eats curd rice. Both lemon rice and curd rice are sour in taste. What is the reason?

Heshna and Keerthi are friends. Keerthi’s teeth are white without caries, but Heshna has teeth with caries. Why? How is it formed?

Classify the various types of Acids based on their sources.

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

Which of the following set of substances contain acids?

State whether the following statements are true or false. Correct the false statements.

Lemon water is basic in nature.

While playing in a park, a child was stung by a wasp. Some elders suggested applying a paste of baking soda and others lemon juice as a remedy. Which remedy do you think is appropriate and why?

When an acidic solution is mixed with a basic solution, they _________ each other forming _________ and water.

Paheli observed that most of the fish in the pond of her village were gradually dying. She also observed that the waste of a factory in their village is flowing into the pond which probably caused the fish to die.

(a) Explain why the fish were dying.

(b) If the factory waste is acidic in nature, how can it be neutralised?

An acid is ______.

Acids are ______ in taste.

Name the acid present in the given table.

The Acid secreted in our stomach is ______.

Curd contains ______ acid. 

Which one of the following acids undergoes complete ionisation?

Complete the following equation.

H+ + H2O → ______.

Complete the following equation.

Na2CO3 + 2HCl → ______ + ______ + CO2

Complete the following equation.

ZnO + 2HCl → ______ + ______.

Complete the following equation.

Zn + ______ → Na2ZnO2 + H2 ↑

Complete the following equation.

CaO + H2SO4 → ______ + H2O

Which is the strongest acid in the following?


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