A student prepared hydrogen chloride gas by treating sodium chloride with concentrated sulphuric acid in a test-tube. He held a strip of dry blue litmus paper in HCl gas coming out of the test-tube. The student observed that on coming in contact with HCl gas, the colour of blue litmus paper :
(1)turned yellow (2)turned violet
(3)remained blue (4)turned red
"

Correct answer: (4) turned red

Explanation: Litmus is an acid-base indicator. Acids turn blue litmus to red and bases turn red litmus to blue. As HCl is an acid, it will turn blue litmus to red.

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Updated on: 10-Oct-2022

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(i) Draw a labelled diagram to show the preparation of hydrogen chloride gas in the laboratory.(ii) Test the gas evolved first with dry and then with wet litmus paper. In which of the two cases, does the litmus paper show change in colour?(iii) State the reason of exhibiting acidic character by dry HCl gas / HCl solution.
Why does dry HCl gas not change the colour of the dry litmus paper?
Michael prepares HCl gas in his school laboratory using certain chemicals. He puts both dry and wet blue litmus papers in contact with the gas.(i) Name the reagents used by Michael to prepare HCl gas. (ii) State the color changes observed with the dry and wet blue litmus paper. (iii) Show the formation of ions when HCl gas combines with water.
Hold one moist and one dry strip of blue litmus paper over dry HCl acid gas. Which strip will turn red and why?
A student placed a pinch of solid sodium hydrogencarbonate on a strip of red litmus paper. He found that the colour of red litmus paper strip :
A student puts a drop of reaction mixture of a saponification reaction first a blue litmus paper and then on a red litmus paper. He may observe that:There is no change in the blue litmus paper and the red litmus paper turns white.There is no change in the red litmus paper and the blue litmus paper turns red.There is no change in the blue litmus paper and the red litmus paper turns blue.No change in colour is observed in both the litmus papers.
Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over the burning sulphur.What will be the action of this gas on:Dry litmus paper?Moist litmus paper?Write a balanced chemical equation for the reaction taking place.
You are provided with three test tubes A, B and C as shown in figure with different liquids. What will you observe when you put(a) a piece of blue litmus paper in each test tube(b) a piece of red litmus paper in each test tube(c) a few drops of phenolphthalein solution to each test tube?
What will be the action of the following substances on litmus paper? Dry HCl gas, Moistened NH3 gas, Lemon juice, Carbonated soft drink, Curd, Soap solution.
(a) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?(b) Dry hydrogen chloride gas does not change the colour of dry litmus paper why?
During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to(a) absorb the evolved gas(b) moisten the gas(c) absorb moisture from the gas(d) absorb Cl– ions from the evolved gas
A student takes Na2CO3 powder in a test tube and pours some drops of acetic acid in it. He observes:(a) No reaction in the test tube. (b) Colourless gas with pungent smell.(c) Bubbles of a colourless and odourless gas. (d) White fumes with smell of vinegar.
A student placed a few drops of a liquid over a portion of the red litmus paper as shown here. He observed that the red litmus paper turned blue. The liquid could be :(1) dilute hydrochloric acid (2) dilute sodium hydroxide(3)water(4)dilute acetic acid"

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(1)turned yellow	(2)turned violet
(3)remained blue	(4)turned red