explain activity 2.9 acid base and salt...class 10th

Dear Student
Activity 2.9 asks us to react solid sodium chloride with concentrated sulphuric acid and check if the gas evolved turn the blue litmus paper into red or not.
Observation: Gas fumes produce, but do not turn the blue litmus paper into the red.
Explanation: Solid sodium chloride reacts with concentrated sulphuric acid and forms dry hydrochloric acid gas.
Here HCl is produced in gaseous form as there is no water.
NaCl(s) + H2SO4(conc.) —> Na2SO(s)+ HCl(g)
A litmus paper works on H+ or OH- ion. Since there is no water in HCl gas, HCl does not dissociate into its ion and does not turn the blue litmus red.
HCl (aq) ——-> H+ + Cl
Inference/Conclusion: Concentrated acids and bases need an aqueous medium to turn litmus paper.


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