21. Solving a chemistry problem

68. A portion of the test technical sample containing an ammonium salt was heated with a certain volume (V NaOH) of a titrated sodium hydroxide solution until the ammonia was completely removed. A certain HCl (V HCl) was used to neutralize the excess alkali. Determine the mass fraction of ammonia in the sample.
Table 4
Problem No. Sample weight, g Volume of NaOH, cm3 Concentration of NaOH Volume of HCl, cm3 Concentration of HCl
68 0.3092 35.00 N=0.09038 18.00 N=0.1000