The answer is starch because iodine reacts with starch to change the colour to inky blue or black.
All the others are present in milk naturally so I’m assuming they intent starch
<span> Ice was soon being harvested from contaminated water sources. Microbes in the ice invaded the food and people became ill
</span>so <span>unsanitary ice is your answer i hope this helps</span>
5.8 is 11.2% of what number
51.786 grams
If you do not this, I suggest brushing up on delocalization as well as sigma/pi bonds. Benzene is the only one of the 5 with any pi bonds, so this should be a relatively easy question if you are familiar with the concepts. I would search up a detailed (not to detailed though) explanation of both.
NH3 = water (it is actually a water soluble gas)
C6H14 = CCl4 (C6H14 won't mix with water at all)
Na2S = water (Na2S is a salt. Salts dissolve best in water)
Br2 = CCl4, but it will also dissolve in water.