Question

The pH of a solution containing 2.0 mole HNO2 and 2.0 mole NaNO2 in 1.0 L of solution will not change by:

a. adding KNO₂.

b. adding Mg(NO₃)₂

c. adding HCl.

d. adding NH₄NO₃.

e. adding HNO₂.

Answer 1

This is a buffer so:

pH = pKA + log(conjugate/acid)

conjugate = NO-2

acid = HNO2

a. adding KNO2. --> adding KNO2; will increase conjugate, therefore, changes log(ratio) which finally changes pH; this is not an answer

b. adding Mg(NO3)2--> since NO3- is not the same as NO2-

c. adding HCl. --> produces more acid from the conjugate; will change pH

d. adding NH4NO3. since NO3- is not the same as NO2-; ithis could be an answer but NH4+ in solution will interact as a base/acid therefore, will mofdify pH

e. adding HNO2. --> increases direclty acid concentration