Consider the following problem:
Target: 2NOCl (g) ¡æ N2 (g) + O2 (g) + Cl2 (g) ¥ÄHrxn= ?
Steps:
1. ¨ö N2(g) + ¨ö O2(g) ¡æ NO(g) ¥ÄH= 90.3 kJ
2. NO(g) + ¨ö Cl2(g) ¡æ NOCl(g) ¥Ä 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
To determine the ΔHrxn value for the target equation, we need to manipulate the given equations in order to cancel out the intermediate reactants and products.
In step 2, we have the equation: NO(g) + ½ Cl2(g) → NOCl(g) ΔH = -38.6 kJ.
We can see that in the target equation, 2NOCl(g) is a product. To match the coefficients, we need to double the equation in step 2.
So, multiplying the equation in step 2 by 2, we get: 2NO(g) + Cl2(g) → 2NOCl(g).
Therefore, the correct answer is: b. Step 2 should be only multiplied by 2.