Which of the following salts have a ph value lesser than 7?
Na2CO3
NaCl
AlCl3
(NH4)2CO3
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Heya friend!!
Rajdeep here....
When you add water on these salts, they hydrolyze, giving an acid and a base:
1. Na2CO3 + H2O --------> NaOH + H2CO3
We know, sodium hydroxide is a strong base and carbonic acid is a weak acid. So influence of the base is more, due to which Na2CO3 solution is basic in nature, so it's pH value is MORE THAN 7.
2. NaCl + H2O ------> NaOH + HCl
We know, NaOH is a strong base and HCl is a strong acid, so both neutralize each other, due to which NaCl solution is neutral. Hence, its pH value is NEARLY EQUAL TO 7.
3. AlCl3 + H2O ------> Al(OH)3 + HCl
We know, Al(OH)3 is a weak base and HCl is a strong acid, hence influence of acid is more due to which AlCl3 solution is acidic. So it's pH value is LESS THAN 7.
4. (NH4)2CO3 + H2O -----> NH4OH + H2CO3
NH4OH, though a weak base, is an alkali, but H2CO3 is a weak acid, hence ammonium carbonate solution in basic, so its pH value is MORE THAN 7.
Your answer is 3. AlCl3.
Thanks!!
Rajdeep here....
When you add water on these salts, they hydrolyze, giving an acid and a base:
1. Na2CO3 + H2O --------> NaOH + H2CO3
We know, sodium hydroxide is a strong base and carbonic acid is a weak acid. So influence of the base is more, due to which Na2CO3 solution is basic in nature, so it's pH value is MORE THAN 7.
2. NaCl + H2O ------> NaOH + HCl
We know, NaOH is a strong base and HCl is a strong acid, so both neutralize each other, due to which NaCl solution is neutral. Hence, its pH value is NEARLY EQUAL TO 7.
3. AlCl3 + H2O ------> Al(OH)3 + HCl
We know, Al(OH)3 is a weak base and HCl is a strong acid, hence influence of acid is more due to which AlCl3 solution is acidic. So it's pH value is LESS THAN 7.
4. (NH4)2CO3 + H2O -----> NH4OH + H2CO3
NH4OH, though a weak base, is an alkali, but H2CO3 is a weak acid, hence ammonium carbonate solution in basic, so its pH value is MORE THAN 7.
Your answer is 3. AlCl3.
Thanks!!
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