How does a conjugate base differ from the acid hbr?
According to the Brønsted–Lowry theory, an acid is a proton donor, and a base is a proton acceptor. Thus, HBr is an acid because it reacts with water according to the equation
HBr + H₂O → H₃O⁺ + Br⁻
In the process, the HBr has donated a proton (H⁺) to the water, and the water has accepted the proton. The HBr is a Brønsted acid, and the water is a Brønsted base.
In the Brønsted-Lowry theory, a conjugate base is whatever is left over after the proton has left. Thus, HBr lost a proton to become Br⁻, so Br⁻ is the conjugate base of HBr.
A conjugate base always has one less H atom and one more negative charge than the original acid. Thus, for example, you can easily say that the conjugate base of H₂O is OH⁻.