Question

Which of the following 0.10 m aqueous solutions gives the lowest pH?

1) HCl
2) NaOH
3) NH₃
4) H₂SO₄

Answer 1

The 0.10 m aqueous solution that gives the lowest pH among those listed is H₂SO₄, because it is a strong diprotic acid and will contribute to a higher concentration of hydrogen ions compared to the monoprotic acid HCl.

Step-by-step explanation:

To answer this, we must know that the pH is a measure of the hydrogen ion concentration in a solution. Strong acids like HCl and H₂SO₄will completely dissociate in water, leading to a high concentration of hydrogen ions and thus a

low pH. Out of the given options, both HCl and H₂SO₄ are strong acids, but H₂SO₄ is a diprotic acid, which means it can donate two protons (hydrogen ions) per molecule as opposed to HCl, which can donate only one. Therefore, H₂SO₄ will result in a higher concentration of hydrogen ions, making the solution more acidic and giving it the lowest pH.

When arranging the solutions in order of most acidic to basic, the order is:

1. H₂SO₄
2. HCl
3. NaCl, NH4NO3 (neutral)
4. NaCN
5. NaOH

Here, NaOH is the most basic and will have the highest pH.

Answer 2

The 0.10 M aqueous solution of H₂SO₄ has the lowest pH as it is a strong diprotic acid. To order the solutions from most acidic to basic, H₂SO₄ is the most acidic, NaOH is the most basic, with NH4NO3 as weakly acidic and NaCN as weakly basic.

Step-by-step explanation:

The 0.10 M aqueous solution that will give the lowest pH among HCl, NaOH, NH₃, and H₂SO₄ is H₂SO₄ because it is a strong acid that is also diprotic, meaning it can donate two protons (H+) per molecule, doubling the concentration of hydronium ions compared to a monoprotic acid like HCl.

To arrange the solutions NaOH, NaCN, H₂SO₄, NH4NO3, NaCl from most acidic to basic, we consider that H₂SO₄ is a strong acid and thus most acidic, NaOH is a strong base and thus most basic, and the others are either salts or neutral. Based on their intrinsic properties, the order would be: H₂SO₄ > NH4NO3 (since NH4+ acts as a weak acid) > NaCl (neutral) > NaCN (weakly basic due to the CN- ion) > NaOH.

Recalling that strong acids and bases completely ionize in solution, while weak acids and bases do not, helps determine the relative pH levels. For instance, the pH of a 1.0 x 10-3M solution of a strong acid such as HCl would be 3, and it would be acidic, while the pH of a 1.0 x 10-7M solution of a strong acid/base would indicate a neutral pH of 7. For strong bases like NaOH, as shown in the example, a 0.10 M solution would have a pH of 13, being very basic.