Andrea is performing two experiments to measure the correlation between sunlight exposure and fish activity. in one experiment, she uses a tank of goldfish in her home. she places the tank in the window on a sunny day and then on a cloudy day, each time recording the average amount of swimming done by the fish during several sample time intervals. in the second experiment, she observes the fish in the pond in her yard on two days, one sunny and one cloudy, and counts the number of times the fish surface looking for food during several time intervals.

which is a scientifically significant similarity between these experiments?
a) lack of controls
b) careful measurements
c) the use of domesticated fish
d) the same independent variable

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

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.