Would you expect the following reactions to be spontanious at high temperatures,
ID: 840100 • Letter: W
Question
Would you expect the following reactions to be spontanious at high temperatures, low temperatures, or not at all? Explain your choice.
1)PCl3(g) + Cl2(g) --> PCl5(s) H* = -87.9 kJ
2) 2 N2O(g) ---> 2N2(g) + O2(g) H* = -164.1 kJ
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The molar mass of aluminum sulfite Al2(SO3)3 is 294.15 g/mol.
1) How man moles of Al2(SO3)3 are in 4.23 grams of Al2(SO3)3?
2) How many alumminum ions are present in .637 moles of Al2(SO3)3? (please show work)
3) How many grams of oxygen are present in a 1.25 mole sample of Aluminum sulfite? (please show work)
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=How many mL of a .200 M methanol solution are needed to make 150 mL of a 0.0375 M methanol solution? (please show work so I can understand how it was done)
Explanation / Answer
1)PCl3(g) + Cl2(g) --> PCl5(s) H* = -87.9 kJ
A reaction is spontaneous if dG < 0
we know that
dG = dH - TdS
Given dH < 0
now look at the reaction
calculate dn
dn = moles of gaseous products - moles of gaseous reactants
dn = 1-2
dn = -1
As dn <0 , dS < 0
for the reaction to be spontaneous
dH - TdS < 0
As dH < 0 and dS <0
is possible only at low values of T
so the reaction is spontaneous at low temperatures
2) 2 N2O(g) ---> 2N2(g) + O2(g) H* = -164.1 kJ
A reaction is spontaneous if dG < 0
we know that
dG = dH - TdS
Given dH < 0
now look at the reaction
calculate dn
dn = moles of gaseous products - moles of gaseous reactants
dn = 3-2
dn = 1
As dn > 0 , dS > 0
for the reaction to be spontaneous
dH - TdS < 0
As dH < 0 and dS > 0
is possible only at any values of T
so the reaction is spontaneous at all temperatures
3) moles = mass /molar mass
moles = 4.23 / 294.15
moles = 0.01438
Al2(S03)3 ---> 2 Al3+ + 3 S032-
so
moles of Al+3 = 2 x moles of Al2(S03)3
moles of Al+3 = 2 x 0.637
moles of Al+3 = 1.274
Given Al2(S03)3
mass of oxygen in 1 mole of Al2(S03)3 = 9 x 16 = 144
mass of oxygen in 1.25 mole of Al2(S03)3 = 144 x 1.25 = 180 g
4) apply M1V1 = M2V2
V1 x 0.2 = 0.0375 x 150
V1 = 28.125
so 28.125 ml is required
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