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.
i> The reagents used are solid sodium chloride (NaCl) and concentrated sulphuric acid (H2SO4).
ii> Dry litmus paper will show no color change.
Wet blue litmus paper changes to red.
iii> The reaction showing the formation of ions are given below:
$HCl+H_{2} O\rightarrow \ \ H_{3} O^{+} \ +\ Cl^{-}$
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- 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 :
- Why does dry HCl gas not change the colour of the dry litmus paper?
- Hold one moist and one dry strip of blue litmus paper over dry HCl acid gas. Which strip will turn red and why?
- 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 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.
- Name the gas evolved when dilute HCl reacts with sodium hydro-carbonate. How is it recognized?
- Why does HCL gas show its acidic nature only when it dissolves in water?
- Name the gas evolved when a metal reacts with water.
- Draw the electron-dot structure of a hydrogen chloride molecule:(i) Which inert gas does the H atom in HCl resemble in electron arrangement? (ii) Which inert gas does the Cl atom in HCl resemble in electron arrangement?
- When a piece of limestone reacts with dilute HCl, a gas X is produced. When gas X is passed through water, then a white precipitate Y is formed. On passing excess of gas X, the white precipitate dissolves forming a soluble compound Z.(a) What are X, Y and Z?(b) Write equations for the reactions which takes place:(i) when limestone reacts with dilute HCl(ii) when gas X reacts with limewater to form white precipitate Y.(iii) when excess gas X dissolves white precipitate Y to form a soluble compound Z.
- (a) What is produced if an acid is added to a base?(b) Why does dry HCl gas not change the colour of dry litmus paper?(c) What colour does phenolphthalein indicator turn when added to an alkali (such as sodium hydroxide)?
- What is the name of the process due to which dry ice changes into carbon dioxide gas?
- (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?
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