The amount of nitrogen in an organic substance can be determined by an analytica

Question

The amount of nitrogen in an organic substance can be determined by an analytical method called the Kjeldahl method, in which all the nitrogen in the organic substance is converted to ammonia. The ammonia, which is a weak base, can be neutralized with hydrochloric acid, as described by the equation NH3(aq) + HCl(aq) NH4Cl(aq) If 75.0 mL of 0.150 M HCI(aq) is needed to neutralize all the NH3(g) from a 2.25-g sample of organic material, calculate the mass percentage of nitrogen in the sample. Number 6 Previous Give Up & View Solution Check Answer Next Exit Hint

Explanation / Answer

moles of HCl reacted = molarity * volume

= 0.150 M * 75.0 mL

= 0.150 M * 0.0750 L

= 0.01125 mol

Since 1 mol of HCl reacts with 1 mol of NH3

So,

mol of NH3 reacted = 0.01125 mol

Molar mass of NH3 = 1*MM(N) + 3*MM(H)

= 1*14.01 + 3*1.008

= 17.034 g/mol

we have below equation to be used:

mass of NH3,

m = number of mol * molar mass

= 0.01125 mol * 17.034 g/mol

= 0.192 g

Mass % of NH3 = mass of NH3*100/mass of sample

= 0.192*100/2.25

= 8.53 %

Answer: 8.53 %

Feel free to comment below if you have any doubts or if this answer do not work

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