Question

In: Chemistry

How many grams of dry NH4Cl need to be added to 2.10 L of a 0.400...

How many grams of dry NH4Cl need to be added to 2.10 L of a 0.400 M solution of ammonia, NH3, to prepare a buffer solution that has a pH of 8.58? Kb for ammonia is 1.8×10−5. Express your answer with the appropriate units.

Expert Solution

PH = 8.58

POH = 14-PH

= 14-8.58 = 5.42

PKb = -logKb

= -log1.8*10^-5

= 4.75

n0 0f moles of NH3 = molarity * volume in L

= 0.4*2.1 = 0.84 moles

POH = PKb + log [salt]/[base]

5.42 = 4.75 + log[NH4Cl]/0.84

5.42-4.75 = log[NH4Cl]/0.84

0.67 = log[NH4Cl]/0.84

[NH4Cl]/0.84 = 10^0.67 = 4. 678

[NH4Cl] = 4.678*0.84 = 3.9295 moles

mass of NH4Cl = no of moles * gram molar mass

= 3.9295*53.5 = 210.2gm >>>> answer

queen_honey_blossom answered 2 years ago

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