The iupac name for a carboxylic acid with two carbons in a straight chain would be

ethanoic acid

Explanation:

For two carbon atom used eth

For saturated hydrocarbon or C-C  single bond  used ane means name is eth +ane = ethane

For –COOH used  -oic acidby Replace the –e ending so the name becomes ethanoic acid

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na