Question

while veryfying the law of conservation of mass,a student carried out a reaction between sodium chloride and silver nitrate in a conical flask. Name the compound which will form as precipitate

Answer 1

The silver nitrate test that there was an anion present in the solution, that will cause silver cations to precipitate. 
Silver usually precipitates as chloride, but also as bromide, iodide and others salts. 
As you have used HCl and NaOH solutions, it must be the chloride. 

The overall reaction you have had there was: 
AgNO3 (aqueous) + NaCl (aqueous) -----> AgCl (white precipitate) + NaNO3 (aqueous) 

or, in a ionic form: 

Ag+ (aqueous) + Cl- (aqueous) -----> AgCl (white precipitate)

Answer 2

Sodium chloride (NaCl) and silver nitrate (AgNO3) are both solids that are highly soluble in water. They give a double displacement reaction where the ions switch places and givesodium nitrate (NaNO3) and silver chloride (AgCl) as the products.