Question #0f450

1 Answer
Oct 28, 2015

Answer:

#K_b=1.8xx10^(-10)color(white)(x)"mol/l"#

Explanation:

We can firstly find the #pK_a# value using this expression for a weak acid:

#pH=1/2(pK_a-logc)#

Where #c# is the concentration of the acid.

#2.5=1/2pK_a-1/2log(0.18)#

#2.5=1/2pK_a+0.372#

#1/2pK_a=2.128#

#pK_a=4.256#

We now use the relationship:

#pK_a+pK_b=14#

#pK_b=14-4.256=9.744#

This means that #-logK_b=9.744#

From which #K_b=1.8xx10^(-10)color(white)(x)"mol/l"#