Many metals corrode. An experiment is carried out to see if magnesium ribbon wrapped around a piece of iron rod has an effect on the rate at which the iron

rod rusts. The apparatus is shown in Figure 4. The method used is an iron rod, with magnesium ribbon wrapped around it, is placed in a boiling tube labelled A 10 cm3 water from a measuring cylinder is poured into this boiling tube an identical rod but with no magnesium ribbon wrapped around it is placed in a second boiling tube labelled B Both boiling tubes are left for a few days. (i) Explain why iron rod rather than stainless steel rod is used in this experiment. (iii) After a few days the two boiling tubes were examined. (ii) State why it is not necessary to use a pipette to measure out 10 cm3 water in this experiment.