Thursday, April 29, 2021

Acids, Bases and Salts | Class 10 | Activity 2.5 with Solution

Activity 2.5
  • Take two test tubes, label them as A and B.
  • Take about 0.5 g of sodium carbonate (Na2CO3) in test tube A and about 0.5 g of sodium hydrogen carbonate (NaHCO3) in test tube B.
  • Add about 2 mL of dilute HCl to both test tubes.
  • What do you observe?
✅ Answer: CO2 gas is produced in both test tubes.

Test tube A:

Na2CO3(s) + 2HCl(aq) 2NaCl(aq) + H2O(l) + CO2(g)

Test tube B:

NaHCO3(s) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g) 

  • Pass the gas produced in each case through lime water (calcium hydroxide solution) as shown in Fig. 2.2 and record your observations.
Fig. 2.2


✅ Answer: On passing CO2 through lime water (calcium hydroxide), lime water becomes milky.

Ca(OH)2(aq) + CO2(g) CaCO3(s) + H2O(l)

            (Lime water)                     (White precipitate)

On passing excess CO2lime water becomes clear due to the formation of soluble calcium bicarbonate.

CaCO3(s)+ H2O(l)+ CO2(g) Ca(HCO3)2(aq)
                                                         (Soluble in water) 

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