Ka for NH4^+ ion is 5.6x10^-10 at 25 oC. Which of the following combinations of reagents...

Question

Question

Ka for NH4^+ ion is 5.6x10^-10 at 25 oC. Which of the following combinations of reagents will produce a buffer with pH=8.85 ?

a) 1 mol NH4Cl and .4 mol NH3

b) 1.4 mol NH4Cl and .4 mol NaOH

c) 1 mol HCl and 1.4 mol NH3

d) all of these

e) none of these

Answer 1

Answer #1

Option A 1mol and 0.4 mol is the correct option.

You can find the option,

Either by calculation
or by the definition of a buffer solution! Buffer solutions are made of either weak acid and its salt(Acid buffer) or a weak base and its salt(basic buffer). Only option A is eligible with the definition.

Now, to prove this by calculation, we use the Henderson-Hasselbalch equation as below-

Answer 2

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