Question #57f4c
1 Answer
Here's how you can think about this.
Explanation:
For a compound that acts as a Bronsted - Lowry acid, the conjugate base is the species formed after the initial compound donates a proton,
You can look at this from another perspective - if by adding a proton to a chemical species you end up with the initial Bronsted - Lowry acid, then that species is the acid's conjugate base.
Simply put, you get the conjugate base of a Bronsted - Lowry acid by removing one proton, which is the same as a hydrogen ion,
Take a look at the first compound, hydrochloric acid. In aqueous solution, hydrochloric acid donates its proton to water, which acts as a base, to form hydronium ions,
#"HCl"_text((aq]) + "H"_2"O"_text((l]) -> "H"_3"O"_text((aq])^(+) + "Cl"_text((aq])^(-)#
So, which chemical species is the conjugate base of hydrochloric acid?
As you can see, the hydrochloric acid molecule donated its proton to a water molecule. So what remained behind? The chloride anion,
This means that you have
#overbrace("HCl"_text((aq]))^(color(red)("acid")) + overbrace("H"_2"O"_text((l]))^(color(blue)("base")) -> overbrace("H"_3"O"_text((aq])^(+))^(color(blue)("conjugate acid")) + overbrace("Cl"_text((aq])^(-))^(color(red)("conjugate base"))#
How about the conjugate base for hydrogen sulfide,
The exact same principle applies. Take away of its protons to get
#"H"_2"S"_text((aq]) + "H"_2"O"_text((l]) -> "H"_3"O"_text((aq])^(+) + "HS"_text((aq])^(-)#
The conjugate base for hydrogen sulfide is the bisulfite anion,
You reform the acid
I'll leave the third one to you as practice.
Keep in mind, for neutral compounds, taking away one proton will always result in a negative charge on the resulting anion, so don't forget about the charge when writing the chemical formula of the conjugate base.