Write the formulas of the conjugate acids of the following Brønsted-Lowry bases.
A.C4H4N−
B.(SO4)2−
C.(CH3)3N
Write the formulas of the conjugate bases of the following Brønsted-Lowry acids.
A.HCN
B.(CH3)2NH2+
C.H2SO4
D.HSO4−
C5H5N
To write the formulas of the conjugate acids of the given Brønsted-Lowry bases, you will need to add a proton (H+) to each base. The conjugate acid is formed by accepting a proton.
A. C4H4N− + H+ → C4H5N
The conjugate acid of C4H4N− is C4H5N.
B. (SO4)2− + H+ → HSO4−
The conjugate acid of (SO4)2− is HSO4−.
C. (CH3)3N + H+ → (CH3)3NH+
The conjugate acid of (CH3)3N is (CH3)3NH+.
To write the formulas of the conjugate bases of the given Brønsted-Lowry acids, you will need to remove a proton (H+) from each acid. The conjugate base is formed by donating a proton.
A. HCN → CN−
The conjugate base of HCN is CN−.
B. (CH3)2NH2+ → (CH3)2NH
The conjugate base of (CH3)2NH2+ is (CH3)2NH.
C. H2SO4 → HSO4−
The conjugate base of H2SO4 is HSO4−.
D. HSO4− → SO42−
The conjugate base of HSO4− is SO42−.
To find the formulas of the conjugate acids of Brønsted-Lowry bases and the formulas of the conjugate bases of Brønsted-Lowry acids, you need to understand the concept of conjugate acids and bases.
In Brønsted-Lowry acid-base theory, a Brønsted-Lowry acid is a species that donates a proton (H+ ion) in a chemical reaction, and a Brønsted-Lowry base is a species that accepts a proton. A conjugate acid is the species formed when a base accepts a proton, and a conjugate base is the species formed when an acid donates a proton.
To write the formula of a conjugate acid, you need to add a proton (H+) to the base. To write the formula of a conjugate base, you need to remove a proton (H+) from the acid.
Let's go through each of the given compounds:
A. C4H4N−:
To find the formula of its conjugate acid, add a proton (H+):
C4H4N− + H+ → C4H5N
B. (SO4)2−:
To find the formula of its conjugate acid, add a proton (H+):
(SO4)2− + 2H+ → H2SO4
C. (CH3)3N:
To find the formula of its conjugate acid, add a proton (H+):
(CH3)3N + H+ → (CH3)3NH+
Now let's move on to the formulas of the conjugate bases of the given Brønsted-Lowry acids:
A. HCN:
To find the formula of its conjugate base, remove a proton (H+):
HCN → CN−
B. (CH3)2NH2+:
To find the formula of its conjugate base, remove a proton (H+):
(CH3)2NH2+ → (CH3)2NH2
C. H2SO4:
To find the formula of its conjugate base, remove a proton (H+):
H2SO4 → HSO4−
D. HSO4−:
To find the formula of its conjugate base, remove a proton (H+):
HSO4− → SO42−
By following these steps, you can determine the formulas of the conjugate acids and bases for a given set of Brønsted-Lowry acid-base pairs.
Students often are confused by Bronsted=Lowry acid/base theory but here is an easy way to remember it. Look at ANY pair. The acid will be the one with more H atoms. Bases will be the one with the smaller number of H atoms.
From above:
Write the formulas of the conjugate bases of the following Brønsted-Lowry acids.
A.HCN
B.(CH3)2NH2+
C.H2SO4
D.HSO4−
So for A we take the H off and have CN^-.
For B. so we take off the H (from the N) to leave (CH3)2NH
For C, take H off to leave HSO4^-
etc.
For the second part add the H to find the acid.