Apattern that has been established based on verified experimental data that describes an observation but does not provide an explanation as to the reason why said observation occurs is a

Hypothesis

Explanation:

This is a hypothesis. A hypothesis is simply a scientific guess to explain a particular phenomenon. It provides different approaches to which an observation can be verified and properly ascertained.

If we can deduce a pattern from a set of experimental data that we have but we have not explained why the observations occur, this is still within the phase of the scientific method called hypothesis.

given:

mass of na = 115 g

excess cl2

to determine:

mass of nacl produced

explanation:

given reaction is-

2na(s) + cl2(g) → 2nacl(s)

since cl2 is in excess, na will be the limiting reagent

as per the reaction stoichiometry na: nacl = 1: 1

i.e. moles of na reacted = moles of nacl formed

now, # moles of na = mass of na/atomic mass

                                  = 115 g/23 g.mol-1 = 5 moles

therefore, moles of nacl = 5

molar mass of nacl = 58 g/mol

mass of nacl = 5 moles * 58 g.mol-1 = 290 g

ans: amount of nacl produced = 290 g