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+HCL------------->NH4CL

If 33.0 mL of 0.150 M HCl(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

2.Lead(II) nitrate and ammonium iodide react to form lead(II) iodide and ammonium nitrate according to the reaction

What volume of a 0.250 M NH4I solution is required to react with 887 mL of a 0.540 M Pb(NO3)2 solution?

How many moles of PbI2 are formed from this reaction?

If you cant answer completely please do not answer at all!!!!! thank you :)

Explanation / Answer

1)

moles of HCl = 33 x 0.150 / 1000 = 4.95 x 10^-3

moles of NH3 = moles of HCl = 4.95 x 10^-3

moles of N = moles of NH3 = 4.95 x 10^-3

mass of N = moles x molar mass

                = 4.95 x 10^-3 x 14

               = 0.0693 g

mass percent of nitrogen = mass of nitrogen x 100 / sample mass

                                          = 0.0693 x 100 / 2.25

                                         = 3.08 %

2)

Pb(NO3)2 + 2 NH4I ----------------------> PbI2 + 2NH4NO3

M1V1/n1 = M2V2/n2

0.540 x 887 / 1 = 0.250 x V2 / 2

V2 = 3832 mL

volume of NH4I = 3832 mL

moles of PbI2 formed = 0.540 x 887 / 1000

                                   = 0.479

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