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
HNO3 ?
Don't forget to include leading zeros before a .
The solution with the lowest pH will be the most acidic, i.e. that with the highest [H+].
A solution with the highest [H+] wil be the solution of the strong acid as it is completely ionised - which is that?
To determine the solution with the lowest pH, we need to look at the nature of the substances and their behavior when dissolved in water. pH measures the concentration of hydrogen ions (H+) in a solution. The higher the concentration of H+, the lower the pH.
Let's analyze each option:
A. 0.10 M HCN: Hydrogen cyanide (HCN) is a weak acid. Weak acids do not completely dissociate in water, so they have a low concentration of H+ ions. The pH of this solution will not be extremely low.
B. 0.10 M HNO3: Nitric acid (HNO3) is a strong acid. Strong acids completely dissociate in water, producing a high concentration of H+ ions. The pH of this solution will be low.
C. 0.10 M NaCl: Sodium chloride (NaCl) is a salt. Salts are formed by the reaction of an acid and a base, and they do not directly contribute to the concentration of H+ ions in solution. The pH of this solution will be neutral (around 7).
D. 0.10 M H2CO3: Carbonic acid (H2CO3) is a weak acid. Similar to HCN, it does not completely dissociate in water, so the concentration of H+ ions is relatively low. The pH of this solution will not be extremely low.
E. 0.10 M NaOH: Sodium hydroxide (NaOH) is a strong base. Strong bases like NaOH dissociate completely in water, generating a high concentration of OH- ions. The pH of this solution will be high (above 7).
Among the given options, 0.10 M HNO3 (option B) will have the lowest pH because it is a strong acid that will generate a high concentration of H+ ions in solution.
To determine which solution will have the lowest pH, we need to look at the nature of the substances and the ions they produce when dissolved in water.
pH is a measure of hydrogen ion concentration in a solution. The lower the pH value, the higher the concentration of hydrogen ions and the more acidic the solution.
Let's analyze each of the given solutions and identify the substances and ions they produce when dissolved in water:
A. .10 M HCN (Hydrocyanic acid): When HCN is dissolved in water, it produces H+ ions and CN- ions. The H+ ions make the solution acidic.
B. .10 M HNO3 (Nitric acid): When HNO3 is dissolved in water, it dissociates into H+ ions and NO3- ions, making the solution acidic.
C. .10 M NaCl (Sodium chloride): NaCl does not dissociate into H+ or OH- ions when dissolved in water, so it does not affect the pH significantly. It is a neutral substance.
D. .10 M H2CO3 (Carbonic acid): When H2CO3 is dissolved in water, it dissociates into H+ ions and HCO3- ions, making the solution acidic.
E. .10 M NaOH (Sodium hydroxide): NaOH dissociates into Na+ ions and OH- ions when dissolved in water. The presence of OH- ions makes the solution basic, not acidic.
Now let's compare the options. Options A, B, and D all produce H+ ions when dissolved in water, making the solutions acidic. However, HNO3 is a strong acid, meaning it dissociates completely, producing a higher concentration of H+ ions than HCN or H2CO3. Therefore, option B, .10 M HNO3, will have the lowest pH.
To summarize, the solution with the lowest pH among the given options is .10 M HNO3 (option B).