Given:
<span> 2.1 moles of chlorine gas (Cl2) at standard temperature and pressure (STP)
Required:
volume of CL2
Solution:
Use the ideal gas law
PV = nRT
V = nRT/P
V = (2.1 moles Cl2) (0.08203 L - atm / mol - K) (273K) / (1 atm)
V = 47 L</span>
The fomula is NH4 (1+)
There are only two elements N and H.
As per oxidation state rules, the most electronegative element will have a negative oxidation state and the other element will have a positive oxidation state.
N is more electronative than H, so H will have a positive oxidation state and nitrogen will have a negative oxidation state.
You can also use the rule that states the hydrogen mostly has 1+ oxidation state,except when it is bonded to metals.
In conclusion the oxidation state of H in NH4 (1+) is 1+.
Now you must know that the sum of the oxidations states equals the charge of the ion, which in this case is 1+.
That implies that 4* (1+) + x = 1+
=> x = (1+) - 4(+) = 3-
Answer: the oxidation state of N is 3-, that is the option b.
Methane is the compound CH4, and burning it uses the reaction:
CH4 + O2 -> CO2 + H2O, which is rather exothermic. To find the heat released by burning a certain amount of the substance, you should look at the bond enthalpy of each compound, and then compare the values before and after the reaction. In methane, there are 4 C-H bonds, which have bond energy of 416 kj/mol, resulting in a total bond energy of 1664 kj/mol. O2 is 494 kj/mol. Therefore we have a total of 2080 kj/mol on the left side. On the right side we have CO2, which has 2 C=O bonds, each at 799 kj/mol each, resulting in 1598 kj/mol, and H2O has 2 O-H bonds, at 459kj/mol each, resulting in a total of 2516 kj/mol on the right hand side. Now, this may be confusing because the left hand side seems to have less heat than the right, but you just need to remember: making minus breaking, which results in a total change of 436kj/mol heat evolved.
Now it is a simple matter of find the mols of CH4 reacted, using n=m/mr.
n = 9.5/16.042 = 0.592195 mol
Therefore, if we reacted 0.592195 mol, and we produced 436 kj for one mol, the total amount of energy evolved was 436*<span>0.592195 kj, or 258.197 kj.</span>
