Which of the following mixtures will result in the formation of a buffer solution if all solutions are 1.0 M before mixing?
i) 100. mL of NH3(aq) and 100. mL of HCl(aq).
ii) 100. mL of NH3(aq) and 50. mL of HCl(aq).
iii) 100. mL of NH3(aq) and 50. mL NaOH(aq).
iv) 100. mL of NH4Cl(aq) and 100. mL of NH3(aq).
v) 100. mL of NH4Cl(aq) and 50. mL of NaOH(aq).
a. ) i and ii
b. ) i and iv
c. ) ii and v
d. ) ii, iii, and v
e. ) ii, iv, and v
I strongly think it's (ii) and (v), but I'm unsure of (iv)
For a basic buffer you want a weak base (NH3) and a salt of the weak base (NH4Cl) since the acid being mixed is always HCl.
Just reason through to see if you have a weak base and its salt.
NH3 + HCl ==> HCl
i. 100 mmoles (mL x M) NH3 and 100 mmoles HCl. Exactly neutral, no excess of either; therefore, no buffer.
ii. 100 mmoles NH3 + 50 mmoles HCl gives 50 mmoles NH4Cl and uses 1/2 leaving 50 mmoles NH3. Both NH3 and NH4Cl present; therefore, buffer.
iii. 100 mmoles NH3 and 50 mmoles NaOH, no salt formation; therefore, no buffer.
iv. 100 mmoles NH4Cl + 100 mmoles NH3. Both base and salt present; therefore, buffer.
v. 100 mL NH4Cl + 50 mmoles NaOH.
NH4Cl + NaOH ==> NaCl + H2O + NH3
All NaOH used.
produces 50 mmoles NH3 and leaves 50 mmoles NH4Cl; therefore, NH4Cl and NH3 present in final mixture and it is buffered.
OK?
Thank you
0.7
To determine which mixtures will result in the formation of a buffer solution, we need to consider the components required for a buffer. A buffer solution consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
Let's analyze each mixture:
i) 100 mL of NH3(aq) and 100 mL of HCl(aq)
- NH3 is a weak base, and HCl is a strong acid.
- This mixture does not contain a weak acid or its conjugate base, so it will not form a buffer solution.
ii) 100 mL of NH3(aq) and 50 mL of HCl(aq)
- Same as before, NH3 is a weak base, and HCl is a strong acid.
- This mixture does not contain a weak acid or its conjugate base, so it will not form a buffer solution.
iii) 100 mL of NH3(aq) and 50 mL of NaOH(aq)
- NH3 is a weak base, and NaOH is a strong base.
- This mixture contains a weak base (NH3) and its conjugate acid (NH4OH).
- This mixture can form a buffer solution.
iv) 100 mL of NH4Cl(aq) and 100 mL of NH3(aq)
- NH4Cl is a salt of NH4+, which is the conjugate acid of NH3, a weak base.
- NH3 is a weak base, and NH4Cl is its conjugate acid.
- This mixture contains a weak base (NH3) and its conjugate acid (NH4Cl).
- This mixture can form a buffer solution.
v) 100 mL of NH4Cl(aq) and 50 mL of NaOH(aq)
- Similar to the previous mixture, NH4Cl is a salt of NH4+ (conjugate acid of NH3).
- NH3 is a weak base, and NaOH is a strong base.
- This mixture contains a weak base (NH3) and its conjugate acid (NH4Cl).
- This mixture can form a buffer solution.
Based on the analysis, the mixtures that will result in the formation of a buffer solution are (iii) 100 mL of NH3(aq) and 50 mL of NaOH(aq), (iv) 100 mL of NH4Cl(aq) and 100 mL of NH3(aq), and (v) 100 mL of NH4Cl(aq) and 50 mL of NaOH(aq).
Therefore, the correct option is (d) ii, iii, and v.