Answer: BF3
Explanation: boron needs 4 electron to obtain octet and Fluorine has just one. For the valence shell to be completely filled it will have to form BF4- with 4 fluorine atom surrounding it.
The states of matter is solid,liquid and gas & you go from there.
Answer:
In Chemistry, Dobereiner triads are defined as, any of several sets of three chemically same elements, the atomic weight of one, which is nearly equal to the mean of the atomic weights of the other two elements.
Answer:a) 11.34 g of ethane 
can be formed
b) 
is the limiting reagent
c) 3.44 g of the excess reagent remains after the reaction is complete
Explanation:
To calculate the moles :
1. 
2. 
According to stoichiometry :
1 mole of require 1 mole of 
Thus 0.378 moles of will require=
of
Thus is the limiting reagent as it limits the formation of product and is the excess reagent.
moles of left = (2.10-0.378) = 1.72 moles
mass of left=
According to stoichiometry :
As 1 mole of give = 1 mole of 
Thus 0.378 moles of give = of
Mass of 
Thus 11.34 g of ethane is formed.
