I think the answer is accuracy
1.) A compound is a thing that is composed of two or more (separate) elements.
2.) A compound cannot be separated easily, while its properties differ from where it originates from. It also is formed from chemical reactions.
3.) A pure substance, also known as chemical substance, is a material with constant composition and consistant properties.
4.) If a substance is not a pure substance, then it is an impure substance.
Hope this helped. :)
Well the IUPAC naming system is for naming organic compounds in chemistry whereas the taxonomic hierarchical naming system is for classifying and naming species of organisms and finding relationships in terms of physical characteristics. The only way I'd say that they're similar is in the way they actually name the compound/species. E.g, in chemistry, you always have a base name and to that base name you can add a suffix and/or prefix(es). And in biology, you always have the first bit of the me which is the generic name and the second bit of the name which is the specific name. I know this probably wasn't very helpful but this is a very odd question if it's one that would be in an exam because chemistry and biology wouldn't usually be mixed together...
Answer:
Enthalpy change for the dissolution of the unknown solid = 4.6 Kj/mole
Explanation:
Using Q = m x Cs x ΔT ................................(1)
where Q = Amount of heat absorbed
m = Mass of solution
Cs = Specific heat capacity of solution
ΔT = Change in temperature
Given Density of solution = 1.20 g/ml
And volume of solution = 150 ml
Mass of solution = density x volume
= 1.2 x 150
= 180 g
From equation (1)
Q = 180 x 4.18 x 19.2 = 14446.08 = 14.4 Kj
So, ΔH of the dissolution of the unknown solid = 
= 
= 4.6 kj/mole
