Question

Refer to aqueous solutions containing 1:1 mole ratios of the following pairs of substances. Assume all concentrations are 1 M.

Answer 1

Answer:

c) HCl and NaCl

Explanation:

Since all the solutions are on a 1:1 mole ratio the comparison is straight forward.

The lowest pH will be for solution c) which has a strong acid, HCl, which ionizes 100 % and the neutral salt NaCl (which is neutral since it is derived from the reaction of the strong acid HCl and the strong base NaOH).

Solutions a) and b) are buffers of  the weak base NH₃ and its conjugate acid NH₄⁺ and weak acid H₃PO₄ and its conjugate weak base NaH₂PO₄ respectively.

Solution c) is a basic solution being a mixture of the weak base NH₃ and the strong base NaOH

Solution e) is a mixture of a weak base NH₂ and weak acid HC₂H₃O₂

Answer 2

Answer:

HCl and NaCl option c

Explanation:

 According to the pH scale interpretation a lower pH means that its is more acidic, while a higher pH means that it is more basic.

Simply put a pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is basic.

From the question above c fits in the option with the lower pH meaning its a strong acid and it tends more towards 0 than 7.

A solution, containing a buffer, is one that maintains a relatively constant pH.

NH3 and NH4Cl ;H3PO4 and NaH2PO4 are an acid/base conjugate pair each. They will make an excellent buffer.

NaOH and NH3 would rather make a slightly basic mixture

NH2 and HC2H3O2 (acetic acid) slightly basic mixture ..

Solution c has the lowest pH.