{b} In experiment B. the iron filings weighed 2.0g at the beginning of the experiment
and the iron sulphide produced weighed 2.8g.
Explain this increase in mass.

Explanation:

The increase in mass is because the iron fillings have combined with a sulfide to produce iron sulfide and so the mass will increase.

In such a reaction like this, the mass of the reactants must be conserved. By so doing, the mass of reactants and products must be the same.

When two substances combine together, their masses added up to that of the individual masses. This helps to conserve the mass.

93.2 ml + 3920 ml = 4013 ml total  

(93.2 ml) * (2.03 m) / (4013 ml) = 0.0471 m

the volume in in l of the diluted solution would be 0.0471 m.

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.