Which compounds MUST be present? Explain why. (Write the formulae and present yo

Question

Which compounds MUST be present? Explain why. (Write the formulae and present your evidence.):

Which compounds MUST be absent? Explain why. (Write the formulae and present your evidence.):

Which compounds are INDETERMINATE - unable to determine if present or absent. (Write the formulae.):

A sample consists of one or more of the following salts: BaCl2, Li2CO3, NaNO3. The sample dissolves completely in water and when dilute HCl is added to this solution, effervescence is seen.

Which compounds MUST be present? Explain why. (Write the formulae and present your evidence.):

Which compounds MUST be absent? Explain why. (Write the formulae and present your evidence.):

Which compounds are INDETERMINATE - unable to determine if present or absent. (Write the formulae.):

Explanation / Answer

a) Li2CO3 must be present

Because Li2CO3 react with HCl to give LiCl , CO2 and H2O

CO2 gas is the reason for effervescence

Li2CO3(aq) + 2HCl(aq) -----> 2LiCl(aq) + CO2(g) + H2O(l)

b) NaNO3 must ba a sent

If NaNO3 present it will react with HCl

NaNO3 + HCl ------> NaCl + HNO3

and HNO3 react with Li2CO3(which is reaponsible for the efferevescence)

HNO3 + Li2CO3 ------> LiHCO3(aq) + LiNO3(aq)

So, no effervescence will occur

c) H2CO3 is intermediate

Li2CO3(aq) + 2HCl(aq) -------> H2CO3(aq) + 2LiCl

H2CO3 ( Carbonic acid ) is unstable and decomposes in to CO2 and H2O

H2CO3(aq) -------> H2O(l) + CO2(g)

  

  

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