Which solution will have the lowest pH ?

A. .10 M HCN
B. .10 M HNO3
C. .10 M NaCL
D. .10 M H2CO3
E. .10 M NaOH

To determine which solution will have the lowest pH, we need to identify the solution that is the strongest acid.

The pH of a solution is a measure of its acidity. A lower pH indicates a higher concentration of H+ ions and a stronger acid.

Let's evaluate each option:

A. 0.10 M HCN: HCN is a weak acid, so it will not dissociate completely in water. It will produce some H+ ions, but not as many as a strong acid. Thus, the pH will be higher compared to a strong acid.

B. 0.10 M HNO3: HNO3 is a strong acid that will dissociate completely in water, producing a high concentration of H+ ions. This solution will have a low pH.

C. 0.10 M NaCl: NaCl is a salt and does not directly contribute to the concentration of H+ ions. It will not significantly affect the pH of the solution.

D. 0.10 M H2CO3: H2CO3 is a weak acid and will not dissociate completely in water. It will produce some H+ ions but not as many as a strong acid. The pH will be higher compared to a strong acid.

E. 0.10 M NaOH: NaOH is a strong base and will dissociate completely in water, producing a high concentration of OH- ions. The pH of this solution will be high, indicating basicity, rather than acidity.

Therefore, the solution with the lowest pH is B. 0.10 M HNO3.

To determine which solution will have the lowest pH, we need to look at the nature of the given substances. The pH scale ranges from 0 to 14, with 0 being the most acidic and 14 being the most basic (alkaline). pH less than 7 indicates an acidic solution, whereas a pH greater than 7 indicates a basic solution.

Let's consider the given options:

A. 0.10 M HCN (hydrogen cyanide): HCN is a weak acid, so it will ionize partially in water to release H+ ions. Therefore, it will have a relatively low pH.

B. 0.10 M HNO3 (nitric acid): HNO3 is a strong acid that completely dissociates in water to release H+ ions. It will have a low pH.

C. 0.10 M NaCl (sodium chloride): NaCl is a salt and does not dissociate to release H+ or OH- ions. It is a neutral substance and will have a pH close to 7.

D. 0.10 M H2CO3 (carbonic acid): H2CO3 is a weak acid that partially ionizes in water to release H+ ions. It will have a low pH, but it is not as strong as HNO3.

E. 0.10 M NaOH (sodium hydroxide): NaOH is a strong base that completely dissociates in water to release OH- ions. It will have a high pH, around 14, indicating a basic solution.

Comparing the options, we see that options A (HCN) and B (HNO3) are acidic solutions, with option B being a stronger acid. Therefore, option B, 0.10 M HNO3, is the answer and will have the lowest pH.