Consider the following problem:
Target: 2NOCl(g) ? N2(g)+ O2(g)+Cl2 (g) ?Hrxn= ?
Steps:
1. 1/2 N2(g) + 1/2 O2(g)? NO(g) ?H= 90.3 kJ
2. NO(g) + 1/2 Cl2(g) ? NOCl(g) ?H= -38.6 kJ
As you determine the ¥ÄHrxn value for the target equation above, what must be done to step 2?
Question options:
a. Step 2 requires no change
b. Step 2 should be only multiplied by 2
c. Step 2 should be reversed and multiplied by 1/2.
d. Step 2 should be reversed and multiplied by 2.
e. Step 2 should be only reversed
d. Step 2 should be reversed and multiplied by 2.
To determine the ΔHrxn value for the target equation, we need to manipulate the given steps accordingly. Let's analyze Step 2:
Step 2: NO(g) + 1/2 Cl2(g) → NOCl(g) ΔH = -38.6 kJ
Comparing this equation to the target equation:
2NOCl(g) → N2(g) + O2(g) + Cl2(g)
We can see that Step 2 needs to be modified to match the stoichiometry of the target equation. The target equation has twice the amount of NOCl compared to Step 2. Therefore, we need to reverse Step 2 and multiply it by 2 to obtain the correct stoichiometric coefficients.
Revised Step 2: 2NOCl(g) → 2NO(g) + Cl2(g) ΔH = 2 * (-38.6 kJ) = -77.2 kJ
So, the correct answer is:
d. Step 2 should be reversed and multiplied by 2.