Which of the following has the HIGHEST
pKa?
1. HClO3
2. HBrO
3. HClO
4. HIO
5. HClO4
HClO3 and HClO4 are both strong acids, and therefore will not have the highest pKa. Between Cl, Br, and I the LEAST electronegative is I, meaning it wont pull the electrons towards itself as much as Cl or Br, so it wont weaken the H bond as much. HIO has the highest pKa.
To determine which of the following compounds has the highest pKa, we need to compare their acid strength. The higher the pKa value, the weaker the acid.
1. HClO3: Chloric acid (HClO3) is a strong acid, meaning it completely ionizes in water and has a low pKa.
2. HBrO: Hypobromous acid (HBrO) is a weak acid and has a higher pKa than HClO3.
3. HClO: Hypochlorous acid (HClO) is a weaker acid than HBrO and has a higher pKa.
4. HIO: Iodic acid (HIO) is a stronger acid than the previous compounds mentioned and has a lower pKa.
5. HClO4: Perchloric acid (HClO4) is the strongest acid among the options and has the lowest pKa.
Therefore, the compound with the HIGHEST pKa is HClO.
To determine which of the given compounds has the highest pKa, we need to understand what pKa is and how it relates to acid strength.
The pKa value is a measure of the acidity of a compound or molecule. It represents the logarithm (base 10) of the acid dissociation constant (Ka), which is a measure of how readily an acid donates a proton (H+) in a solution. In general, the lower the pKa value, the stronger the acid, and the higher the pKa value, the weaker the acid.
Now, let's compare the given compounds:
1. HClO3 (Chloric acid): Chloric acid is a strong acid with a pKa value of around -1. It is highly dissociated in water and is therefore a strong acid.
2. HBrO (Hypobromous acid): Hypobromous acid is a weak acid with a pKa value of around 8.7. It only partially dissociates in water and is considered a weak acid.
3. HClO (Hypochlorous acid): Hypochlorous acid is a weak acid with a pKa value of around 7.5. Like hypobromous acid, it only partially dissociates in water.
4. HIO (Hypoiodous acid): Hypoiodous acid is a weak acid with a pKa value of around 10.4. It is weaker than both hypobromous acid and hypochlorous acid.
5. HClO4 (Perchloric acid): Perchloric acid is a strong acid with a pKa value of around -10. It is highly dissociated in water and is therefore a strong acid.
From the given options, HClO4 (perchloric acid) has the lowest pKa value (-10). Therefore, it has the highest acidity and is the strongest acid among the provided choices.
The highest pKa value means the weakest acid. Why not look up the Ka or pKa values and see.
http://clas.sa.ucsb.edu/staff/Resource%20Folder/Chem109ABC/Acid,%20Base%20Strength/Table%20of%20Acids%20w%20Kas%20and%20pKas.pdf