# Enthalpy question help

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#1
Hydrogen iodide, HI, is a colourless gas that can be made from the reaction of hydrogen, H2, and iodine, I2.

H2(g) + I2(g) 2HI(g) ΔH = −9 kJ mol−1
The activation energy for the forward reaction is 173 kJ mol−1.

(b) Calculate the activation energy, Ea, for the reverse reaction.
The answer for this was +182

(c) When the reverse reaction takes place hydrogen iodide, HI, decomposes to form iodine and hydrogen.
Calculate the enthalpy change when 336 dm3 of hydrogen iodide, measured at room temperature and pressure, decomposes.
enthalpy change .................................................... kJ [2]

The answer is +63KJ but I don't understand how they got this. Any help would be appreciated thanks!
0
3 years ago
#2
(Original post by Lia22)
Hydrogen iodide, HI, is a colourless gas that can be made from the reaction of hydrogen, H2, and iodine, I2.

H2(g) + I2(g) 2HI(g) ΔH = −9 kJ mol−1
The activation energy for the forward reaction is 173 kJ mol−1.

(b) Calculate the activation energy, Ea, for the reverse reaction.
The answer for this was +182

(c) When the reverse reaction takes place hydrogen iodide, HI, decomposes to form iodine and hydrogen.
Calculate the enthalpy change when 336 dm3 of hydrogen iodide, measured at room temperature and pressure, decomposes.
enthalpy change .................................................... kJ [2]

The answer is +63KJ but I don't understand how they got this. Any help would be appreciated thanks!
What is the enthalpy change per mol of HI for the reverse reaction?

How many moles are actually involved?
0
#3
(Original post by charco)
What is the enthalpy change per mol of HI for the reverse reaction?

How many moles are actually involved?
I worked out the moles as 14
0
3 years ago
#4
(Original post by Lia22)
I worked out the moles as 14
Don't forget that the equation expressed (H2 + I2 <-> 2HI) involves 2 mol of HI.
0
1 year ago
#5
There are 14 miles of 2HI.Now what I did was divide them by 2 which gave me 7 and then multiplied it by 9 (enthalpy change in the reverse reaction), which gave me 63 kJ/mol
0
1 month ago
#6
Where did you get 14 moles from?
0
1 month ago
#7
(Original post by 14.suthasanA)
Where did you get 14 moles from?
Volume/24
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