give reason for:
1. Iron in iron (ii) sulphide does not give hydrogen gas with dilute acid.
2. During crystallisation, the hot saturated solution is gradually cooled .
3. Silver nitrate solution is kept in dark coloured bottles in the laboratory.
4. An atom is ellectrically neutral.
5. Chlorine atoms form chloride ions or CL- ions.
Answers
Answer:
1: FeS formed reacts with sulphuric acid to form ferrous sulphate and release hydrogen di sulphide gas.
So there is no hydrogen evolved in this reaction
2 : Gradual cooling involves dissolving the impure solid in a minimum amount of a hot solvent and
allowing the resulting solution to cool slowly to room temperature. During the cooling process,
pure (or almost pure) crystals form and are then collected by vacuum filtration. Thus it is gradually cooled.
3 : With sunlight it decomposes to silver and silver oxide that can easily precipitate out. Therefore to prevent the photo-dissociation of molecule, silver nitrate solution is kept in a laboratory in coloured reagent bottles so that no direct contact will occur with sunlight that will prevent the dissociation of molecules
4 : Atoms are electrically neutral because they have equal numbers of protons (positively charged) and electrons (negatively charged).
5 : A chlorine atom seven electrons in the outer shell. A sodium atom loses an electron to a chlorine atom. The sodium atom becomes a positive sodium ion. The chlorine atom becomes a negative chloride ion.