In: Physics
Suppose you have 2.0mol of O2 gas.
How many coulombs of positive charge are contained in this gas in the atomic nuclei?
Express your answer using two significant figures
you're right in noting that the net charge of the gas is zero:
however, this is because it contains equal amounts of positive
nuclear charge and negative electron charge, and not because no
charges are present.
Just treating the positive nuclear charges as their own entity, we
need to know that:
(1) Oxygen has atomic number 8, and so each oxygen atom contains
eight protons. Consequently, the O2 molecule contains sixteen
protons.
(2) Each proton carries a charge of 1.602 x 10^(-19) C (see
"elementary charge").
(3) One mole of O2 gas contain's 6.022 x 10^(23) (Avogadro's
number) molecules of O2.
Hence, the total positive charge of two mol O2 can be computed
by:
(2.0 mol O2) * (6.022 x 10^(23) molecules/mol) * (16
protons/molecule) * (1.602 x 10^(-19) C/proton)
= 3.1 x 10^6 C [1]
Of course, the total negative charge of the gas is equal to 3.1 x
10^6 C as well, and consequently the gas is neutral as a whole.