Near water, change in elevation, or change in latitude.
Answer:
b. 1.5 atm.
Explanation:
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In this case, since the undergoing chemical reaction suggests that two moles of A react with one moles of B to produce two moles of C, for the final pressure we can write:

Now, if we introduce the stoichiometry, and the change in the pressure
we can write:

Nevertheless, since the reaction goes to completion, all A is consumed and there is a leftover of B, and that consumed A is:

Thus, the final pressure is:

Therefore the answer is b. 1.5 atm.
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The equilibrium vapour pressure is typically the pressure exerted by a liquid .... it is A FUNCTION of temperature...
Explanation:
By way of example, chemists and physicists habitually use
P
saturated vapour pressure
...where
P
SVP
is the vapour pressure exerted by liquid water. At
100
∘
C
,
P
SVP
=
1
⋅
a
t
m
. Why?
Well, because this is the normal boiling point of water: i.e. the conditions of pressure (i.e. here
1
⋅
a
t
m
) and temperature, here
100
∘
C
, at which the VAPOUR PRESSURE of the liquid is ONE ATMOSPHERE...and bubbles of vapour form directly in the liquid. As an undergraduate you should commit this definition, or your text definition, to memory...
At lower temperatures, water exerts a much lower vapour pressure...but these should often be used in calculations...especially when a gas is collected by water displacement. Tables of
saturated vapour pressure
are available.
Its FeSO3 or iron(iii)sulfite = Fe2(SO3)3