Well, an independent variable ids the thing that stays the same and a dependent variable is the thing that changes.
The variable would be the distance you dropped them.
Answer:
5.6 seconds
Explanation:
The reaction follows a zero-order in dinitrogen monoxide
Rate = k[N20]^0 = change in concentration/time
[N20]^0 = 1
Time = change in concentration of N2O/k
Initial number of moles of N2O = 300 mmol = 300/1000 = 0.3 mol
Initial concentration = moles/volume = 0.3/4 = 0.075
Number of moles after t seconds = 150 mmol = 150/1000 = 0.15 mol
Concentration after t seconds = 0.15/4 = 0.0375 M
Change in concentration of N2O = 0.075 - 0.0375 = 0.0375 M
k = 0.0067 M/s
Time = 0.0375/0.0067 = 5.6 s
The answer to your question is Gallium, or GA. The trick is to always check if they are along the same vertical column. This indicates that they have the same Valence electrons, which is involved in all the bonding and define the electronegative status of the atom.