Answer: d) -705.55 kJ
Explanation:
Heat of reaction is the change of enthalpy during a chemical reaction with all substances in their standard states.

Reversing the reaction, changes the sign of 


On multiplying the reaction by
, enthalpy gets half:


Thus the enthalpy change for the given reaction is -705.55kJ
.......When they yield the same amount , *Reversible reactions* will reach chemical equilibrium........
Answer:
The mass was there all along, it was just in the air. The weight of the oxygen from the air is not weighed in the beginning, only at the end as part of the product, making it seem like there is a total mass change.
Explanation:
(a) The given data is as follows.
T =
= (55 + 273) K
= 328 K
P = 35 bar = 3500 kPa
Let us assume that moles of ethylene present are 1 kmol and according to the ideal gas equation, PV = nRT.
Or, V = 
= 
= 0.779 
Hence, the volume occupied by 18 kg of ethylene at
and 35 bar is 0.779
.
(b) The given data is as follows.
V = 0.25 
T =
= (50 + 273) K
= 323 K
P = 115 bar = 11500 kPa
Using ideal gas equation first, we will calculate its moles as follows.
n = 
= 
= 1.07 mol
Since, moles = 
Hence, mass of ethylene will be calculated as follows.
moles = 
1.07 mol = 
mass = 29.96 g
Therefore, mass of given ethylene is 29.96 g.
Problem 2
You start out with 216 ugrams of Fermium - 253. After 3 days, you will have 1/2 as much. 108 ugrams is what you have.
Another 3 days goes by. You started with 108 ugrams. That gets cut in 1/2 again. Now you have 54 ugrams.
Finally another 3 days goes by. You started with 54 ugrams. you now have 1/2 as much which would be 27 ugrams
#days Amount in micrograms
0 216
3 108
6 54
9 27
Problem One
You are using Nitrogen as your base example. The first thing you should do is fill in the table. Then you should try and make some rules. You need the rules in case the exam you are preparing for picks a different element to talk about these bond tendencies. In any event, it's handy to think this way.
<em><u>Table</u></em>
Bond Energy Kj/Mol Bond Length pico meters
N - N 167 145
N=N 418 125
N≡N 942 110
<em><u>Rules</u></em>
As the number of bonds INCREASES, the energy contained in the bond goes UP
As the number of bonds INCREASES, the length of the bond goes DOWN.