Molar Mass AgNO, 169.87 g.mol 8. To prepare 250.0 mL of a 0.07500 M solution of

Question

Molar Mass AgNO, 169.87 g.mol 8. To prepare 250.0 mL of a 0.07500 M solution of AgNO, from the solid reagent, what mass of reagent must be used? (A) 3.183 g (C) 75.00g (B) 5.662g (D) 18.75 9. A 1.234 g sample of cod Atomic Molar Mass fish was analyzed by the Kjeldahl method for mass percent nitrogen. In this 14.007 g.mol procedure, organie nitrogen is converted into ammonia gas, which is collected and titrated with a standard HCI solution. The liberated ammonia required 25.75 mL of 0.1339 M HCI to reach an endpoint. Calculate the mass percent of nitrogen in the sample. (A) 0.4255% (C) 3.914% (B) 7.830% (D) 4.214%

Explanation / Answer

8) Molarity(M) = (w/M)*(1000/V)

       w = mass of solid = ?

      M = molarmass of AgNO3 = 169.87 g/mol

      v = volume of solution = 250 ml

0.075 = (w/169.87)*(1000/250)

w =3.185 g

answer: A

9)
   NH3 + HCl ---> NH4Cl

   no of mol of HCl reacted = 25.75*0.1339/1000 = 0.00345 mol

   no of mol of NH3 reacted = 0.00345 mol

Mass of N present in sample = 0.00345*14.007 = 0.04832 g

% of N in sample = 0.04832/1.234*100 = 3.916%

answer : C

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