Which of the following solutions result in a buffer ?

[SamTsui86]

Homework Statement

2. [1pt]

Which of the following solutions result in a buffer ?



a) 0.100 L of 0.250 M NH3 + 0.050 L of 0.250 M HCl


b) 0.100 L of 0.250 M NH3 + 0.100 L of 0.250 M HCl


c) 0.100 L of 0.250 M NH4Cl + 0.050 L of 0.250 M NaOH


d) 0.100 L of 0.250 M NH4Cl + 0.150 L of 0.250 M NaOH

Homework Equations

M = mol/V

The Attempt at a Solution

so I got the mol for each one, they are

1) .025 mol and .0125 mol
2) .025 mol and .025 mol
3) .025 mol and .0125 mol
4) .025 mol and .0375 mol

I don't know how to do it, please help help

 

[symbolipoint]

Simply check which situation conforms to the definition of a pH buffer. You first know that ammonium and chloride are "completely" ionized in water solution. Now, in which solution exists either a weak base and salt of that base; or an weak acid and a salt of that acid?

 

[Blueshift5]

A buffer solution is one that resists changes in pH when small amounts of acid or base are added. It is made up of a weak acid and its conjugate base, or a weak base and its conjugate acid. In order for a solution to act as a buffer, it must contain significant amounts of both the weak acid/base and its conjugate.

In this case, the solutions that result in a buffer are b) 0.100 L of 0.250 M NH3 + 0.100 L of 0.250 M HCl and d) 0.100 L of 0.250 M NH4Cl + 0.150 L of 0.250 M NaOH. These solutions both contain a weak base (NH3 or NH4Cl) and its conjugate acid (HCl or NaOH) in approximately equal concentrations. This allows the solution to resist changes in pH when small amounts of acid or base are added.